ORCID Profile
0000-0002-8367-4056
Current Organisations
Philips Healthcare
,
Monash Institute of Pharmaceutical Sciences
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Animal Physiology—Systems | Physiology | Veterinary Sciences | Pharmacology and Pharmaceutical Sciences | Pharmacology | Basic Pharmacology | Animal Physiology—Cell
ANZSRC Socio-Economic Objective (SEO)
Biological sciences | Health not elsewhere classified | Treatments (e.g. chemicals, antibiotics) | Expanding Knowledge in the Medical and Health Sciences |
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Publications
THE CONCISE GUIDE TO PHARMACOLOGY 2021/22: G protein-coupled receptors.
Publisher: Wiley
Date: 16-09-2021
DOI: 10.1111/BPH.15538
Abstract: The Concise Guide to PHARMACOLOGY 2021/22 is the fifth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of nearly 1900 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes over 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at oi/bph.15538. G protein-coupled receptors are one of the six major pharmacological targets into which the Guide is ided, with the others being: ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2021, and supersedes data presented in the 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.
Relaxin-like bioactivity of ovine insulin 3 (INSL3) analogues
Publisher: Wiley
Date: 12-2002
DOI: 10.1046/J.1432-1033.2002.03348.X
Abstract: Relaxin is an insulin-like peptide consisting of two separate chains (A and B) joined by two inter- and one intrachain disulfide bonds. Binding to its receptor requires an Arg-X-X-X-Arg-X-X-Ile motif in the B-chain. A related member of the insulin superfamily, INSL3, has a tertiary structure that is predicted to be similar to relaxin. It also possesses an Arg-X-X-X-Arg motif within its B-chain, although this is displaced by four amino acids towards the C-terminus from the corresponding position within relaxin. We have previously shown that synthetic INSL3 itself does not display relaxin-like activity although analogue (Analogue A) with an introduced arginine residue in the B-chain giving it an Arg cassette in the exact relaxin position does possess weak activity. In order to identify further the structural features that impart relaxin function, solid phase peptide synthesis was used to prepare three additional analogues for bioassay. Each of these contained point substitutions within the arginine cassette. Analogue D contained the full human relaxin binding cassette, Analogue G consisted of the native INSL3 sequence containing an Arg to Ala substitution, and Analogue E was a further modification of Analogue A, with the same substitution. Each analogue was fully chemically characterized by a number of criteria. Detailed circular dichroism spectroscopy analyses showed that the changes caused little alteration of secondary structure and, hence, overall conformation. However, each analogue displayed only weak relaxin-like activity. These results indicate that while the arginine cassette is vital for relaxin-like activity, there are additional, as yet unidentified structural requirements for relaxin binding.
Regulation of AMP-activated protein kinase activity by G-protein coupled receptors: potential utility in treatment of diabetes and heart disease.
Publisher: Elsevier BV
Date: 09-2008
DOI: 10.1016/J.PHARMTHERA.2008.05.008
Abstract: G-protein coupled receptors (GPCRs) comprise the largest and most erse family of membrane receptors in the human genome, relaying information from a vast array of external stimuli. GPCRs are targets for approximately 30% of all current therapeutic agents. Recently some GPCRs have been shown to mediate part of their effects through activation of AMP-activated protein kinase (AMPK), a sensor of whole body energy status that plays a pivotal role in whole body energy balance by integrating signals in the periphery and central nervous system. It regulates glucose and lipid metabolism, food intake and body weight, making it an attractive target for the treatment of diseases such as type 2 diabetes and obesity. It mediates the effects of several important adipokines such as leptin and adiponectin and is thought to be responsible for the antidiabetic effects of metformin and thiazolidinediones. A erse number of GPCRs (including adrenoceptors, cannabinoid receptors, ghrelin receptors, melanocortin receptors) modulate AMPK activity. This review focuses on the regulation of AMPK by GPCRs and signaling intermediates of GPCR signaling such as cyclic AMP and calcium, and how GPCR signaling can modulate AMPK activity by several different mechanisms, and the therapeutic implications of AMPK activation by GPCRs.
THE INFLUENCE OF AGE AND SEX ON CARDIAC, RENAL AND CAUDAL ARTERY CATECHOLAMINE CONTENT IN SPONTANEOUSLY HYPERTENSIVE (SHR) AND WISTAR KYOTO (WKY) RATS
Publisher: Wiley
Date: 09-1986
DOI: 10.1111/J.1474-8673.1986.TB00642.X
Abstract: Noradrenaline (NA), adrenaline (A) and dopamine (DA) levels were measured in the heart, kidney and caudal artery of male and female SHR and WKY rats aged 6, 14 and 28 weeks, and the influence of strain, sex and age on catecholamine content determined. Levels of A were elevated in all three regions of SHR compared to WKY rats, independent of age and sex. This may represent increased A accumulation in sympathetic nerves resulting from the increased sympatho-adrenomedullary hyper-reactivity of the SHR strain. DA levels were also elevated in the heart and kidney of SHR rats, independent of sex and age. Na levels were lower in the heart of SHR rats, but this appeared to be partly a consequence of cardiac hypertrophy and partly due to strain difference between older male but not female rats. Thus a simple association between decreased cardiac NA levels and hypertension appeared unlikely. It is emphasised that further genetic studies of F2 backcross rats would be required to establish an etiological association between these differences in catecholamine levels and differences in blood pressure between the SHR and WKY strains.
beta2- and beta3-Adrenoceptors activate glucose uptake in chick astrocytes by distinct mechanisms: A mechanism for memory enhancement?
Publisher: Wiley
Date: 29-06-2007
DOI: 10.1111/J.1471-4159.2007.04789.X
Abstract: Isoprenaline, acting at beta-adrenoceptors (ARs), enhances memory formation in single trial discriminated avoidance learning in day-old chicks by mechanisms involving alterations in glucose and glycogen metabolism. Earlier studies of memory consolidation in chicks indicated that beta3-ARs enhanced memory by increasing glucose uptake, whereas beta2-ARs enhance memory by increasing glycogenolysis. This study examines the ability of beta-ARs to increase glucose uptake in chick forebrain astrocytes. The beta-AR agonist isoprenaline increased glucose uptake in a concentration-dependent manner, as did insulin. Glucose uptake was increased by the beta2-AR agonist zinterol and the beta3-AR agonist CL316243, but not by the beta1-AR agonist RO363. In chick astrocytes, reverse transcription-polymerase chain reaction studies showed that beta1-, beta2-, and beta3-AR mRNA were present, whereas radioligand-binding studies showed the presence of only beta2- and beta3-ARs. beta-AR or insulin-mediated glucose uptake was inhibited by phosphatidylinositol-3 kinase and protein kinase C inhibitors, suggesting a possible interaction between the beta-AR and insulin pathways. However beta2- and beta3-ARs increase glucose uptake by two different mechanisms: beta2-ARs via a Gs-cAMP-protein kinase A-dependent pathway, while beta3-ARs via interactions with Gi. These results indicate that activation of beta2- and beta3-ARs causes glucose uptake in chick astrocytes by distinct mechanisms, which may be relevant for memory enhancement.
Bidirectional transport of NMDA receptor and ionophore in the vagus nerve
Publisher: Elsevier BV
Date: 1989
DOI: 10.1016/0014-2999(89)90668-7
Abstract: Accumulations of binding sites for [3H]3-[+-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic ([3H]CPP) and [3H]-N-(1-[2-thienyl]cyclohexyl)-3,4-piperidine ([3H]TCP) were demonstrated both proximal and distal to 24-h ligatures of the central and peripheral vagus nerve in the rat using radioligand binding and autoradiography. Peaks of label occurred at the proximal and distal extremities of double ligations but not between the ligatures, or in sham-operated or colchicine-treated nerves. Together these results suggest that both the primary acceptor site and the ionophore of the N-methyl-D-aspartate receptor undergo bidirectional axonal transport in central and peripheral branches of the vagus nerve.
Relaxin family peptide receptors - from orphans to therapeutic targets
Publisher: Elsevier BV
Date: 08-2008
DOI: 10.1016/J.DRUDIS.2008.04.002
Abstract: The relaxin family peptides have distinct expression profiles and physiological functions. Several of them are the cognate ligands for 4 G-protein-coupled relaxin family peptide receptors (RXFPs formerly LGR7, LGR8, GPCR135, GPCR142). The relaxin/RXFP1 system has roles in reproductive physiology but is also involved in fibrosis, wound healing and responses to infarction. Relaxin has a potential use in congestive heart failure where fibrosis plays an important role in organ failure. The INSL3/RXFP2 system has biological roles in reproductive biology that may have limited therapeutic potential. However, the recently characterized relaxin-3/RXFP3 system is important in stress/anxiety and body composition. RXFP3 receptor antagonists are potentially novel anti-anxiety and anti-obesity drugs.
[3H]‐CLONIDINE BINDING TO α‐ADRENOCEPTORS IN MEMBRANES PREPARED FROM REGIONS OF GUINEA‐PIG KIDNEY: ALTERATION BY MONOVALENT AND DIVALENT CATIONS
Publisher: Wiley
Date: 1980
DOI: 10.1111/J.1476-5381.1980.TB10909.X
Abstract: 1 [(3)H]-clonidine binds reversibly to membranes prepared from regions of guinea-pig kidney.2 Higher levels of binding were obtained in the membranes prepared from renal cortex (2.15 +/- 0.27 pmol/g wet wt.) than renal medulla (0.53 +/- 0.07 pmol/g wet wt.) or papilla (0.14 +/- 0.06 pmol/g wet wt. n = 4).3 Scatchard analysis performed by addition of unlabelled clonidine (1 to 30 pmol) gave figures for the dissociation constant (K(d)) for the binding of [(3)H]-clonidine to renal cortical membranes of 9.0 +/- 0.8 nM and B(max) of 21.6 +/- 1.7 pmol/g wet wt. (n = 4). Hill plots of these data gave gradients close to unity, indicating a lack of co-operative site interactions.4 The monovalent cations, sodium and potassium, and the alent cation, calcium, produced concentration-dependent decreases in [(3)H]-clonidine binding to membranes prepared from renal cortex, the EC(50)s being respectively 25 mM, 37 mM and 23 mM.5 At low concentrations the alent cations, magnesium (1 mM) and manganese (0.1 mM), produced enhancement of [(3)H]-clonidine binding. At higher concentrations (>10 mM) both alent cations inhibited binding.6 Scatchard analysis of [(3)H]-clonidine binding performed in the presence of sodium (100 mM), magnesium (1 mM) or manganese (0.1 mM) revealed that the alterations in binding are primarily due to changes in apparent affinity rather than a change in the number of binding sites. Sodium (100 mM) produced a change in the K(d) from 7.0 +/- 0.4 nM (n = 8) to 42.3 +/- 27.5 nM (n = 3), whereas magnesium (1 mM) decreased the K(d) to 6.0 +/- 0.9 nM and manganese (0.1 mM) to 4.0 +/- 1.0 nM (n = 3).7 The results indicate that [(3)H]-clonidine labels a binding site that has properties resembling an alpha(2)-adrenoceptor, located in the renal cortex. The changes produced by the addition of monovalent and alent cations are entirely due to changes in the apparent affinity of [(3)H]-clonidine binding.
THE EFFECTS OF α‐ADRENOCEPTOR AGONISTS AND ANTAGONISTS ON RESPONSES OF TRANSMURALLY STIMULATED PROSTATIC AND EPIDIDYMAL PORTIONS OF THE ISOLATED VAS DEFERENS OF THE RAT
Publisher: Wiley
Date: 08-1979
DOI: 10.1111/J.1476-5381.1979.TB13694.X
Abstract: 1 The effects of alpha-adrenoceptor agonists and antagonists on contractile responses of transmurally stimulated prostatic and epididymal portions of the rat isolated vas deferens were examined. 2 Responses to single stimuli consisted of two phases, the first predominant in the prostatic and the second in the epididymal portion. The first phase was resistant to alpha-adrenoceptor antagonists but the second was reduced in a dose-related manner in the order of potency prazosin greater than azapetine greater than phentolamine greater than labetalol greater than yohimbine. 3 Both phases of the response to a single stimulus were reduced by clonidine but only the first could be reliably restored by yohimbine. 4 Trains of transmural stimuli produced biphasic responses, an early rapid component predominant in the prostatic and a slow secondary component predominant in the epididymal portion. The effects of alpha-adrenoceptor antagonists on these responses were complex. Prazosin produced the most straightforward inhibition of responses with relative resistance of the early rapid component. Only yohimbine and phentolamine produced increases in responses which could be pre-junctional in origin. 5 The alpha-adrenoceptor agonists, oxymetazoline and clonidine, reduced while phenylephrine increased responses to trains of stimuli. 6 These results are discussed in relation to the nature of the innervation of rat vas deferens and the usefulness of the preparation in pharmacological tests for activity at alpha-adrenoceptors.
The effects of amiodarone, an α and β receptor antagonist, on adrenergic transmission in the cat spleen
Publisher: Elsevier BV
Date: 05-1976
Kakouris et al. reply
Publisher: Elsevier BV
Date: 06-1993
Autoradiographic demonstration of endothelium-dependent 125I-Bolton-Hunter substance P binding to dog carotid artery
Publisher: Elsevier BV
Date: 05-1986
INVESTIGATION OF THE ROLE OF CALCIUM IN THE SUPER-SENSITIVITYPRODUCED BY COCAINE IN CAT SPLEEN STRIPS
Publisher: Wiley
Date: 04-1979
DOI: 10.1111/J.1476-5381.1979.TB07883.X
Abstract: 1. Cocaine (2 x 10(-6) M and 10(-5) M) produced 2 and 7 fold shifts to the left of the dose-response curve to (-)-noradrenaline recorded isotonically in isolated splenic capsular strips of the cat. 2. The same concentrations of cocaine also produced increases in the maximum response of the tissue to 117% and 126.7% of control. 3. Desmethylimipramine (DMI, 10(-7) to 10(-6) M) produced no significant potentiation of the response of cat spleen strips to (-)-noradrenaline. At 10(-5) M DMI decreased the maximum response. 4. Cocaine (10(-5) M) produced a 3.3 fold shift to the left of the dose-response curve whereas DMI (10(-6) M) had no effect on the dose-response curve to oxymetazoline in cat splenic capsular strips. 5. Cocaine (10(-5) M) in the presence of phentolamine (10(-6) M) produced a shift to the left and an increase in the maximum response to K+, an agonist which is believed to produce muscle contraction by increasing the membrane calcium flux. 6. Cocaine (10(-5 M) had no effect on the dose-response curve to angiotensin which is believed to contract vascular muscle by releasing calcium from intracellular storage sites. 7. The potentiating effect of cocaine (10(-5) M) on responses of spleen strips to (-)-noradrenaline was blocked by the calcium flux inhibitor SKF 525A (2.65 x 10(-5) M). 8. It is concluded that the results are compatible with the view that cocaine enhances the influx of calcium across the cell membrane during responses to agonists that utilize the extracellular pool of calcium and that this effect is responsible for a large part of the potentiation of the response.
Localization of β-adrenoceptors in the rabbit ear by light microscopic autoradiography
Publisher: Elsevier BV
Date: 09-1985
DOI: 10.1016/0014-2999(85)90589-8
Abstract: The beta-adrenoceptor antagonist [125I]cyanopindolol (CYP) was used to localize beta-adrenoceptors in sections of rabbit ear. Biochemical studies demonstrated that the binding was stereoselective, and that the beta-adrenoceptors are predominantly of the beta 2-subtype. Autoradiographic studies using 3H-Ultrofilm or nuclear emulsion coated coverslips showed high concentrations of beta 2-adrenoceptors present in the central ear artery, hyaline cartilage, nerve trunks, epithelium and sebaceous glands.
Adrenoceptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database
Publisher: Edinburgh University Library
Date: 16-09-2019
Abstract: The nomenclature of the Adrenoceptors has been agreed by the NC-IUPHAR Subcommittee on Adrenoceptors [58], see also [180]. Adrenoceptors, α1α1-Adrenoceptors are activated by the endogenous agonists (-)-adrenaline and (-)-noradrenaline. phenylephrine, methoxamine and cirazoline are agonists and prazosin and cirazoline antagonists considered selective for α1- relative to α2-adrenoceptors. [3H]prazosin and [125I]HEAT (BE2254) are relatively selective radioligands. S(+)-niguldipine also has high affinity for L-type Ca2+ channels. Fluorescent derivatives of prazosin (Bodipy PLprazosin- QAPB) are used to examine cellular localisation of α1-adrenoceptors. Selective α1-adrenoceptor agonists are used as nasal decongestants antagonists to treat hypertension (doxazosin, prazosin) and benign prostatic hyperplasia (alfuzosin, tamsulosin). The α1- and β2-adrenoceptor antagonist carvedilol is used to treat congestive heart failure, although the contribution of α1-adrenoceptor blockade to the therapeutic effect is unclear. Several anti-depressants and anti-psychotic drugs are α1-adrenoceptor antagonists contributing to side effects such as orthostatic hypotension and extrapyramidal effects.Adrenoceptors, α2 α2-Adrenoceptors are activated by (-)-adrenaline and with lower potency by (-)-noradrenaline. brimonidine and talipexole are agonists and rauwolscine and yohimbine antagonists selective for α2- relative to α1-adrenoceptors. [3H]rauwolscine, [3H]brimonidine and [3H]RX821002 are relatively selective radioligands. There is species variation in the pharmacology of the α2A-adrenoceptor. Multiple mutations of α2-adrenoceptors have been described, some associated with alterations in function. Presynaptic α2-adrenoceptors regulate many functions in the nervous system. The α2-adrenoceptor agonists clonidine, guanabenz and brimonidine affect central baroreflex control (hypotension and bradycardia), induce hypnotic effects and analgesia, and modulate seizure activity and platelet aggregation. clonidine is an anti-hypertensive and counteracts opioid withdrawal. dexmedetomidine (also xylazine) is used as a sedative and analgesic in human and veterinary medicine with sympatholytic and anxiolytic properties. The α2-adrenoceptor antagonist yohimbine has been used to treat erectile dysfunction and mirtazapine as an anti-depressant. The α2B subtype appears to be involved in neurotransmission in the spinal cord and α2C in regulating catecholamine release from adrenal chromaffin cells.Adrenoceptors, ββ-Adrenoceptors are activated by the endogenous agonists (-)-adrenaline and (-)-noradrenaline. Isoprenaline is selective for β-adrenoceptors relative to α1- and α2-adrenoceptors, while propranolol (pKi 8.2-9.2) and cyanopindolol (pKi 10.0-11.0) are relatively β1 and β2 adrenoceptor-selective antagonists. (-)-noradrenaline, xamoterol and (-)-Ro 363 show selectivity for β1- relative to β2-adrenoceptors. Pharmacological differences exist between human and mouse β3-adrenoceptors, and the 'rodent selective' agonists BRL 37344 and CL316243 have low efficacy at the human β3-adrenoceptor whereas CGP 12177 and L 755507 activate human β3-adrenoceptors [88]. β3-Adrenoceptors are resistant to blockade by propranolol, but can be blocked by high concentrations of bupranolol. SR59230A has reasonably high affinity at β3-adrenoceptors, but does not discriminate well between the three β- subtypes whereas L 755507 is more selective. [125I]-cyanopindolol, [125I]-hydroxy benzylpindolol and [3H]-alprenolol are high affinity radioligands that label β1- and β2- adrenoceptors and β3-adrenoceptors can be labelled with higher concentrations (nM) of [125I]-cyanopindolol together with β1- and β2-adrenoceptor antagonists. [3H]-L-748337 is a β3-selective radioligand [474]. Fluorescent ligands such as BODIPY-TMR-CGP12177 can be used to track β-adrenoceptors at the cellular level [8]. Somewhat selective β1-adrenoceptor agonists (denopamine, dobutamine) are used short term to treat cardiogenic shock but, chronically, reduce survival. β1-Adrenoceptor-preferring antagonists are used to treat hypertension (atenolol, betaxolol, bisoprolol, metoprolol and nebivolol), cardiac arrhythmias (atenolol, bisoprolol, esmolol) and cardiac failure (metoprolol, nebivolol). Cardiac failure is also treated with carvedilol that blocks β1- and β2-adrenoceptors, as well as α1-adrenoceptors. Short (salbutamol, terbutaline) and long (formoterol, salmeterol) acting β2-adrenoceptor-selective agonists are powerful bronchodilators used to treat respiratory disorders. Many first generation β-adrenoceptor antagonists (propranolol) block both β1- and β2-adrenoceptors and there are no β2-adrenoceptor-selective antagonists used therapeutically. The β3-adrenoceptor agonist mirabegron is used to control overactive bladder syndrome.
Chronic activation of the low affinity site of β1‐adrenoceptors stimulates haemodynamics but exacerbates pressure‐overload cardiac remodelling
Publisher: Wiley
Date: 27-08-2013
DOI: 10.1111/BPH.12272
Separate roles for β2- and β3-adrenoceptors in memory consolidation
Publisher: Elsevier BV
Date: 12-1999
DOI: 10.1016/S0306-4522(99)00469-8
Abstract: Consolidation of a labile memory which would not normally be stored can be achieved by intracerebral administration of noradrenaline. In a series of experiments using discriminated, one trial passive avoidance learning with the day-old chick, the effect of noradrenaline has been shown to be due to actions at different subtypes of adrenoceptors. The effect of noradrenaline is dose-dependent, with a moderate dose producing memory consolidation. However, higher doses of noradrenaline (0.3-10 nmol/hemisphere) prevent consolidation, an effect not seen with isoprenaline suggesting that these doses stimulate alpha-adrenoceptors. The promotion of memory consolidation by noradrenaline or isoprenaline at low doses was attributable to beta3-adrenoceptors and at medium doses to beta2-adrenoceptors. At higher doses of noradrenaline, there was alpha1-adrenoceptor-mediated inhibition of memory consolidation. Consolidation can also be achieved by administration of either beta2- or beta3-adrenoceptor agonists at specific times after training. Although these two adrenoceptors both promoted memory consolidation, there was a differential action on the stages of memory formation. The dose-response curve to the beta3- and the beta2-agonists was shifted by the appropriate antagonist but not by the antagonist at the other beta-adrenoceptor. Although beta1-adrenoceptors are present in chick brain, they do not seem to have a role in memory formation. These results explain why noradrenaline, acting at different adrenoceptors, can have different effects on memory formation with memory being either consolidated or inhibited depending on the dose. The findings also demonstrate a role in memory formation for beta3-adrenoceptors found in the brain. Agonists acting specifically at beta2- or beta3-adrenoceptors may be of value in diseases involving cognitive impairment.
The effects of labetalol (AH 5158) on metabolism of 3H(−)-noradrenaline released from the cat spleen by nerve stimulation
Publisher: Elsevier BV
Date: 11-1977
Localization and characterization of two propranolol resistant (-) [125I]cyanopindolol binding sites in rat skeletal muscle
Publisher: Elsevier BV
Date: 12-1991
DOI: 10.1016/0014-2999(91)90179-T
Abstract: Autoradiographic studies were performed in sections of rat gastrocnemius, plantaris and soleus muscle bundles with (-)-[125I]cyanopindolol (59-69 pM) in the presence of (-)-propranolol (1 microM) to block beta 1- and beta 2-adrenoceptors. Two distinct populations of binding sites remained, one evenly distributed over the muscle bundles and the other localized in discrete patches. Evenly distributed binding was highest in the soleus muscle and inhibited by (+/-)-, (-)- and (+)-alprenolol (20 microM), tertatolol (1 microM), BRL 37344 (2-20 microM), (-)-isoprenaline (100 microM), phentolamine (10 microM) and haloperidol (250 microM) but not ICI 118,551 (70 nM), CGP 20712A (100 nM), (+)-isoprenaline (100 microM), pindolol (2 microM), cimaterol (100 microM) or serotonin (10 microM). Stereoselectivity for the optical isomers of alprenolol was displayed in the soleus muscle only. Highly localized binding was inhibited by serotonin (10 microM), (-)- and (+)-isoprenaline (100 microM) and phentolamine (10 microM).
Noradrenaline release in the locus coeruleus modulates memory formation and consolidation; roles for α- and β-adrenergic receptors.
Publisher: Elsevier BV
Date: 11-2010
DOI: 10.1016/J.NEUROSCIENCE.2010.07.052
Abstract: Noradrenaline, essential for the modulation of memory, is released in various parts of the brain from nerve terminals controlled by the locus coeruleus (LoC). Noradrenaline release consequent upon input from higher brain areas also occurs within the LoC itself. We examined the effect of noradrenaline on adrenergic receptors in the LoC on memory processing, using colored bead discrimination learning in the young domestic chick. We have shown previously that the release of noradrenaline in the hippoc us and cortex (mesopallium) is essential for acquisition and consolidation of short-term to intermediate and to long-term memory. Noradrenaline release within the LoC is triggered by the glutamatergic input from the forebrain. Inhibition by LoC injection of NMDA or AMPA receptor antagonists is rescued by injection of β2-and β3-adrenoceptor (AR) agonists in the hippoc us. We show that inhibition of α2A-ARs by BRL44408 in the LoC up to 30 min post-training consolidates weakly-reinforced learning. Conversely activation of α2A-ARs in the LoC at the times of consolidation between short-term and intermediate and long-term memory caused memory loss, which is likely to be due to a decreased release of noradrenaline within these two time windows. The α2A-AR antagonist will block presynaptic inhibitory receptors leading to an increase in extracellular noradrenaline. This interpretation is supported by the actions of noradrenaline uptake blockers that produce the same memory outcome. BRL44408 in the mesopallium also caused memory enhancement. β2-ARs are important in the first time window, whereas α1-, α2C-and β3-ARs are important in the second time window. The results reveal that for successful memory formation noradrenaline release is necessary within the LoC as well as in other brain regions, at the time of consolidation of memory from short-term to intermediate and from intermediate to long-term memory.
Relaxin family peptide receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database
Publisher: Edinburgh University Library
Date: 16-09-2019
DOI: 10.2218/GTOPDB/F60/2019.4
Abstract: Relaxin family peptide receptors (RXFP, nomenclature as agreed by the NC-IUPHAR Subcommittee on Relaxin family peptide receptors [18, 75]) may be ided into two pairs, RXFP1/2 and RXFP3/4. Endogenous agonists at these receptors are heterodimeric peptide hormones structurally related to insulin: relaxin-1, relaxin, relaxin-3 (also known as INSL7), insulin-like peptide 3 (INSL3) and INSL5. Species homologues of relaxin have distinct pharmacology and relaxin interacts with RXFP1, RXFP2 and RXFP3, whereas mouse and rat relaxin selectively bind to and activate RXFP1 [172]. relaxin-3 is the ligand for RXFP3 but it also binds to RXFP1 and RXFP4 and has differential affinity for RXFP2 between species [170]. INSL5 is the ligand for RXFP4 but is a weak antagonist of RXFP3. relaxin and INSL3 have multiple complex binding interactions with RXFP1 [176] and RXFP2 [84] which direct the N-terminal LDLa modules of the receptors together with a linker domain to act as a tethered ligand to direct receptor signaling [173]. INSL5 and relaxin-3 interact with their receptors using distinct residues in their B-chains for binding, and activation, respectively [211, 97].
Memory loss caused by β-amyloid protein is rescued by a β3-adrenoceptor agonist
Publisher: Elsevier BV
Date: 04-2010
DOI: 10.1016/J.NEUROBIOLAGING.2008.05.018
Abstract: Accumulation of the neurotoxic beta-amyloid protein (Abeta) in the brain is a key step in the pathogenesis of Alzheimer's disease (AD). Although transgenic mouse models of AD have been developed, there is a clear need for a validated animal model of Abeta-induced amnesia which can be used for toxicity testing and drug development. Intracranial injections of Abeta(1-42) impaired memory in a single trial discriminative avoidance learning task in chicks. Memory inhibition was closely associated with the state of aggregation of the Abeta peptide, and a scrambled-sequence of Abeta(1-42) peptide failed to impair memory. Abeta had little effect on labile (short-term and intermediate) memory, but blocked consolidation of memory into long-term storage mimicking the type of anterograde amnesia that occurs in early AD. Since noradrenaline exerts a modulatory influence on labile memory in the chick, we examined the effects of two beta-adrenoceptor (AR) agonists on Abeta-induced amnesia. A beta(3)-AR agonist (CL316243), but not a beta(2)-AR agonist, rescued Abeta-induced memory loss, suggesting the need for further studies on the role of beta(3)-ARs in AD.
CHARACTERIZATION AND LOCALIZATION OF [3H]-CLONIDINE BINDING IN MEMBRANES PREPARED FROM GUINEA-PIG SPLEEN
Publisher: Wiley
Date: 02-1982
DOI: 10.1111/J.1440-1681.1982.TB00781.X
Abstract: 1. [3H]-Clonidine binds to membranes prepared from guinea-pig spleen with high affinity. 2. Kinetic experiments indicated that [3H]-clonidine associates rapidly to the binding site and that the binding is reversible. A study of the dissociation of [3H]-clonidine from splenic membranes revealed two components. The slowly dissociating component corresponded to a high affinity process (Kd = 2.1 nmol/l) in good agreement to that obtained by saturation analysis. 3. Over the concentration range used, saturation experiments revealed only a single population of sites with a dissociation constant (Kd) of 2.4 nmol/l and a density of 5.1 pmol/g wet weight tissue. 4. Examination of the relatively potency of a series of alpha-adrenoceptor agonists and antagonists indicates that [3H]-clonidine binding is to alpha 2-adrenoceptors. 5. High levels of binding were obtained to lymphocytes prepared from guinea-pig spleen and to membranes from the splenic capsule. Pretreatment of animals with 6-hydroxydopamine produced changes in apparent affinity of binding with little change in the number of receptor sites. 6. It is concluded that [3H]-clonidine labels is a site resembling the alpha 2-adrenoceptor in guinea-pig spleen. Few if any of these sites are located prejunctionally and a significant fraction are associated with lymphocytes.
Lidocaine and surgical modification reduces mortality in a rat model of cardiac failure induced by coronary artery ligation
Publisher: Elsevier BV
Date: 05-2000
DOI: 10.1016/S1056-8719(00)00103-9
Abstract: Coronary artery ligation in the rat provides a useful experimental model of cardiac failure however, this procedure carries with it a high mortality rate (50%). In this study, we used lidocaine (10 mg/kg, i.m.) before coronary artery ligation and 2 h after surgery to minimise the incidence of ventricular fibrillation (VF) that leads to sudden death in this model. We found that coronary artery ligation, using lidocaine in conjunction with a modified surgical procedure, had a mortality rate of 15%, much lower than reported in previous studies using this model. These modifications allow for the production of larger infarcts with 29% of animals having an infarct size > 50% of the epicardial surface. Infarct size in our myocardial infarction (MI) group varied between 5% and 75% of the left ventricular (LV) surface area resulting in a mean infarct size of 41.3 +/- 1.3% for the epicardial surface and 40.0 +/- 1.3% for the endocardial surface.
α2-adrenoceptors in the basal ganglia have a role in memory consolidation and reinforcement
Publisher: Elsevier BV
Date: 09-2003
DOI: 10.1016/S0028-3908(03)00172-2
Abstract: This study demonstrates a role for alpha(2)-adrenoceptors in the basal ganglia in the consolidation of memory using weakly and strongly reinforced models of discriminated avoidance learning in the chick. The memory enhancing action of noradrenaline injected into the basal ganglia (lobus parolfactorius-LPO) was reduced in the presence of the alpha(2)-adrenoceptor antagonist yohimbine, but when noradrenaline was injected into the multi-modal association area (intermediate medial hyperstriatum ventrale-IMHV), yohimbine failed to prevent memory enhancement. Yohimbine injected into the LPO prevented, whereas the alpha(2)-adrenoceptor agonists oxymetazoline and clonidine enhanced, consolidation of memory. The timing of the inhibitory effect of yohimbine in the LPO suggested that alpha(2)-adrenoceptor involvement occurs 10-15 min after training, and that stimulation of alpha(2)-ARs in LPO is necessary for subsequent consolidation of memory. Oxymetazoline, being hydrophilic, was ineffective injected into IMHV, whereas the action of the lipophilic alpha(2)-adrenoceptor agonist clonidine in the IMHV was interpreted as an action at a site more distal in the brain, probably the LPO. The results suggest that noradrenaline release in the basal ganglia in the chick stimulates alpha(2)-adrenoceptors, which modulate and consolidate memory formation mediated by beta(2)- or beta(3)-ARs in the association area. The LPO may be responsible for the reinforcement of memory in the IMHV.
The Concise Guide to PHARMACOLOGY 2015/16: Overview
Publisher: Wiley
Date: 12-2015
DOI: 10.1111/BPH.13347
ML290 is a biased allosteric agonist at the relaxin receptor RXFP1.
Publisher: Springer Science and Business Media LLC
Date: 07-06-2017
DOI: 10.1038/S41598-017-02916-5
Abstract: Activation of the relaxin receptor RXFP1 has been associated with improved survival in acute heart failure. ML290 is a small molecule RXFP1 agonist with simple structure, long half-life and high stability. Here we demonstrate that ML290 is a biased agonist in human cells expressing RXFP1 with long-term beneficial actions on markers of fibrosis in human cardiac fibroblasts (HCFs). ML290 did not directly compete with orthosteric relaxin binding and did not affect binding kinetics, but did increase binding to RXFP1. In HEK-RXFP1 cells, ML290 stimulated cAMP accumulation and p38MAPK phosphorylation but not cGMP accumulation or ERK1/2 phosphorylation although prior addition of ML290 increased p-ERK1/2 responses to relaxin. In human primary vascular endothelial and smooth muscle cells that endogenously express RXFP1, ML290 increased both cAMP and cGMP accumulation but not p-ERK1/2. In HCFs, ML290 increased cGMP accumulation but did not affect p-ERK1/2 and given chronically activated MMP-2 expression and inhibited TGF-β1-induced Smad2 and Smad3 phosphorylation. In vascular cells, ML290 was 10x more potent for cGMP accumulation and p-p38MAPK than for cAMP accumulation. ML290 caused strong coupling of RXFP1 to Gα s and Gα oB but weak coupling to Gα i3 . ML290 exhibited signalling bias at RXFP1 possessing a signalling profile indicative of vasodilator and anti-fibrotic properties.
Relaxin requires the angiotensin II type 2 receptor to abrogate renal interstitial fibrosis
Publisher: Elsevier BV
Date: 07-2014
DOI: 10.1038/KI.2013.518
Abstract: Fibrosis is a hallmark of chronic kidney disease, for which there is currently no effective cure. The hormone relaxin is emerging as an effective antifibrotic therapy however, its mechanism of action is poorly understood. Recent studies have shown that relaxin disrupts the profibrotic actions of transforming growth factor-β1 (TGF-β1) by its cognate receptor, relaxin family peptide receptor 1 (RXFP1), extracellular signal-regulated kinase phosphorylation, and a neuronal nitric oxide synthase-dependent pathway to abrogate Smad2 phosphorylation. Since angiotensin II also inhibits TGF-β1 activity through its AT2 receptor (AT2R), we investigated the extent to which relaxin interacts with the AT2R. The effects of the AT2R antagonist, PD123319, on relaxin activity were examined in primary rat kidney myofibroblasts, and in kidney tissue from relaxin-treated male wild-type and AT2R-knockout mice subjected to unilateral ureteric obstruction. Relaxin's antifibrotic actions were significantly blocked by PD123319 in vitro and in vivo, or when relaxin was administered to AT2R-knockout mice. While heterodimer complexes were formed between RXFP1 and AT2Rs independent of ligand binding, relaxin did not directly bind to AT2Rs but signaled through RXFP1-AT2R heterodimers to induce its antifibrotic actions. These findings highlight a hitherto unrecognized interaction that may be targeted to control fibrosis progression.
Selectivity of a series of clonidine-like drugs for α1 and α2 adrenoceptors in rat brain
Publisher: Elsevier BV
Date: 12-1980
DOI: 10.1016/0304-3940(80)90172-X
Abstract: Drug dosage forms contain many components in addition to the active pharmaceutical ingredient(s) to assist in the manufacturing process as well as to optimise drug delivery. Due to advances in drug delivery technology, excipients are currently included in novel dosage forms to fulfil specific functions and in some cases they directly or indirectly influence the extent and/or rate of drug release and absorption. Since plant polysaccharides comply with many requirements expected of pharmaceutical excipients such as non-toxicity, stability, availability and renewability they are extensively investigated for use in the development of solid oral dosage forms. Furthermore, polysaccharides with varying physicochemical properties can be extracted from plants at relatively low cost and can be chemically modified to suit specific needs. As an ex le, many polysaccharide-rich plant materials are successfully used as matrix formers in modified release dosage forms. Some natural polysaccharides have even shown environmental-responsive gelation characteristics with the potential to control drug release according to specific therapeutic needs. This review discusses some of the most important plant-derived polymeric compounds that are used or investigated as excipients in drug delivery systems.
Synthesis, conformational studies and biological activity of Να‐mono‐biotinylated rat relaxin*
Publisher: Wiley
Date: 05-2001
DOI: 10.1034/J.1399-3011.2001.00853.X
Abstract: Biotin-avidin immobilization can be a useful tool in structure-function studies of hormone receptors. A crucial step is the preparation of a specifically biotinylated hormone that is able to bind to its receptor while leaving the biotin group free for interaction with avidin. The receptor for relaxin, an ovarian peptidic hormone produced during pregnancy, has not yet been isolated. We therefore undertook to prepare a specifically monobiotinylated rat relaxin for use in ligand-searching strategies. Rat relaxin is a convenient analogue because reliable bioassays exist, thus allowing assessment of the effect of N-biotinylation on bioactivity. To help improve the yield of the two-chain, three-disulfide bond rat relaxin, 2-hydroxy-4-methoxybenzyl (Hmb) backbone protection was used during the solid-phase assembly of the B-chain to help prevent any possible chain aggregation. As a final step, while the protected peptide was still on the resin, the biotin label was introduced at the N-terminus of the B-chain using standard coupling protocols. The chain combination with the A-chain was accomplished in reasonable yield. Secondary structural measurements demonstrated that the biotin caused the starting B-chain to adopt a more ordered conformation. The labelled synthetic relaxin exhibited similar circular dichroism spectra to native and synthetic single B-chain peptides. In addition, the biotinylated relaxin showed no significant difference in its chronotropic activity in the rat isolated heart assay compared with the native peptide. Biosensor studies showed that antibody recognition was retained upon attachment of the synthetic relaxin to the streptavidin-derivatized surface.
Energy metabolism and memory processing: role of glucose transport and glycogen in responses to adrenoceptor activation in the chicken.
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.1016/J.BRAINRESBULL.2008.02.019
Abstract: From experiments using a discriminated bead task in young chicks, we have defined when and where adrenoceptors (ARs) are involved in memory modulation. All three ARs subtypes (alpha(1)-, alpha(2)- and beta-ARs) are found in the chick brain and in regions associated with memory. Glucose and glycogen are important in the role of memory consolidation in the chick since increasing glucose levels improves memory consolidation while inhibiting glucose transporters (GLUTs) or glycogen breakdown inhibits memory consolidation. The selective beta(3)-AR agonist CL316243 enhances memory consolidation by a glucose-dependent mechanism and the administration of the non-metabolized glucose analogue 2-deoxyglucose reduces the ability of CL316243 to enhance memory. Agents that reduce glucose uptake by GLUTs and its incorporation into the glycolytic pathway also reduce the effectiveness of CL316243, but do not alter the dose-response relationship to the beta(2)-AR agonist zinterol. However, beta(2)-ARs do have a role in memory related to glycogen breakdown and inhibition of glycogenolysis reduces the ability of zinterol to enhance memory. Both beta(2)- and beta(3)-ARs are found on astrocytes from chick forebrain, and the actions of beta(3)-ARs on glucose uptake, and beta(2)-ARs on the breakdown of glycogen is consistent with an effect on astrocytic metabolism at the time of memory consolidation 30 min after training. We have shown that both beta(2)- and beta(3)-ARs can increase glucose uptake in chick astrocytes but do so by different mechanisms. This review will focus on the role of ARs on memory consolidation and specifically the role of energy metabolism on AR modulation of memory.
Characterization and localization of atypical β‐adrenoceptors in rat ileum
Publisher: Wiley
Date: 11-1995
DOI: 10.1111/J.1476-5381.1995.TB17206.X
Abstract: 1. Homogenate binding studies and receptor autoradiography have been used to examine the binding characteristics and localization of propranolol-resistant (-)-[125I]-cyanopindolol (CYP) binding sites in rat ileum. 2. Saturation studies with (-)-[125I]-CYP and homogenates of rat ileum identified a site with pKD 8.89 +/- 0.08 and Bmax = 50.3 +/- 4.1 fmol mg-1 protein (n = 6). Both beta 1- and beta 2-adrenoceptors (AR) were not detected in these preparations. 3. (-)-Isoprenaline infusion (400 micrograms kg-1 h-1) for 14 days caused no significant change in the density of (-)-[125I]-CYP binding which was 48.9 +/- 12.8 and 40.6 +/- 12.3 fmol mg-1 protein in control and isoprenaline-treated animals respectively (n = 6) (P = 0.97). 4. Competition for (-)-[125I]-CYP binding in the presence of 0.1 microM (-)-propranolol gave affinity values for CYP, tertatolol, alprenolol, ICI 118551 and CGP 20712A that correspond to known affinities at atypical beta-ARs. Stereoselectivity ratios for tertatolol and alprenolol were low. 5. Autoradiographic localization of propranolol resistant (-)-[125I]-CYP binding showed sites associated with the mucosa and to a lesser extent to the muscularis. A small population of beta 2-ARs were detected located predominantly in the longitudinal and circular smooth muscle layers. 6. This study identifies an (-)-[125I]-CYP binding site in rat ileum that is resistant to blockade by propranolol (0.1 microM), is located predominantly in the mucosa, shows resistance to downregulation by isoprenaline and has binding characteristics of the atypical beta-AR.
ROLE OF CENTRAL β-ADRENOCEPTORS IN THE CONTROL OF PENTYLENETETRAZOL-INDUCED CONVULSIONS IN RATS
Publisher: Wiley
Date: 03-1982
DOI: 10.1111/J.1476-5381.1982.TB09159.X
Abstract: 1 The role of central beta-adrenoceptors in the anticonvulsant effect of beta-adrenoceptor antagonists has been examined. 2 Oral administration of (-)- and (+)-propranolol (0.05-1 mg/kg) and (+/-)-pindolol (0.025-0.5 mg/kg) produced a dose-dependent decrease in duration of convulsions produced by pentylenetetrazol (PTZ 50 mg/kg, i.p.) in rats. 3 At the EC50 level, (-)-propranolol is seven times more effective than the (+)-isomer. 4 Oral administration of (-)-, (+)- or (+/-)-practolol (1-10 mg/kg) or (-)- or (+)-timolol (1-10 mg/kg), two beta-adrenoceptor antagonists that do not penetrate the blood brain barrier, had no significant effect on the duration of PTZ-induced convulsions. 5 Intracerebroventricular administration of (-)-propranolol (0.5 microgram/kg) or (-)-timolol (0.25 microgram/kg) produced highly significant anticonvulsant effects whereas the (+)-isomers at the same dose level were ineffective. (+/-)-Pindolol (0.25 microgram/kg) was also much more effective given by this route than when given orally. The (+)- and (-)-isomers of the beta 1-adrenoceptor selective antagonist practolol (10 microgram/kg) exerted only weak anticonvulsant effects. 6 This study provides evidence that beta-adrenoceptor antagonists exert an anticonvulsant effect through central beta 2-adrenoceptors. At high dose levels, additional anticonvulsant activity is associated with membrane stabilization in those antagonists which possess this property.
Functional and molecular evidence for β1‐, β2‐ and β3‐adrenoceptors in human colon
Publisher: Wiley
Date: 04-1997
[3H]Forskolin binding to cardiac adenylate cyclase in guinea pigs chronically infused with isoproterenol
Publisher: Elsevier BV
Date: 08-1995
DOI: 10.1016/0024-3205(95)02049-O
Abstract: Guinea pigs were infused with the beta-adrenoceptor agonist isoproterenol (400 micrograms/kg/hr, 7 days) and cardiac adenylate cyclase was detected using [3H]forskolin. Two populations of [3H]forskolin binding sites were present in heart, the affinities (KD 2 nM and 280 nM) and densities (Bmax 9 and 900 fmol/mg protein) of which were unchanged by isoproterenol infusion compared with vehicle (1 mM HCl). The autoradiographic localisation of [3H]forskolin binding was also unchanged. The G protein activators NaF 10 mM and 5'-guanylylimidodiphosphate (Gpp(NH)p) 10 microM increased [3H]forskolin binding in heart from vehicle-treated animals by 100% and 80% respectively. NaF-stimulated binding was unchanged in isoproterenol-treated animals, however, Gpp(NH)p-stimulated binding was reduced by 35% which may indicate an increased influence of Gi.
Multiple signalling pathways involved in β2‐adrenoceptor‐mediated glucose uptake in rat skeletal muscle cells
Publisher: Wiley
Date: 02-2006
Role of beta-adrenoceptors in glucose uptake in astrocytes using beta-adrenoceptor knockout mice
Publisher: Wiley
Date: 22-03-2011
THE EFFECTS OF PIPEROXAN ON UPTAKE OF NORADRENALINE AND OVERFLOW OF TRANSMITTER IN THE ISOLATED BLOOD PERFUSED SPLEEN OF THE CAT
Publisher: Wiley
Date: 08-1978
DOI: 10.1111/J.1476-5381.1978.TB17283.X
Abstract: 1 The competitive alpha-adrenoceptor blocking agent, piperoxan, in concentrations up to 2 x 10(-4) M, produced large dose-dependent increases in transmitter overflow from the isolated blood perfused spleen of the cat following nerve stimulation at 10 hertz. 2 At concentrations greater than 2 x 10(-4) M, piperoxan produced a rise in perfusion pressure, a contraction of the splenic capsule, and a marked dose-dependent decrease in transmitter overflow. 3 Phenoxybenzamine (10(-4) M) and desmethylimipramine (3 x 10(-5) M) produced further increases in transmitter overflow when added after piperoxan. 4 Piperoxan (5.8 to 6.6 x 10(-6) M) had no effect on the recovery of 3H in the venous blood following the close arterial infusion or injection of (3H)-(--)-noradrenaline, indicating that the drug does not inhibit uptake of the amine. 5 Piperoxan produced dose-dependent inhibition of responses of the splenic vasculature to close arterial injection of 1 microgram of (--)-noradrenaline but was much less effective at inhibiting responses to nerve stimulation. At 2 x 10(-6) M piperoxan produced a considerable reduction of the response to injected noradrenaline but potentiated the response to nerve stimulation. 6 In isolated strips of cat splenic capsule, piperoxan produced a shift to the right of the dose-response curve to noradrenaline with no change of the maximum response. There was no evidence of a postsynaptic sensitizing effect of the type observed in the rat vas deferens.
β2-Adrenoceptor-mediated regulation of glucose uptake in skeletal muscle--ligand-directed signalling or a reflection of system complexity?
Publisher: Springer Science and Business Media LLC
Date: 09-05-2013
DOI: 10.1007/S00210-013-0879-7
Abstract: The capacity of G protein-coupled receptors (GPCRs) to activate multiple G protein isoforms and additional effectors such as β-arrestins has become a well-established paradigm and provides the basis for developing drugs that preferentially activate beneficial signalling pathways. There are many published ex les of ligand-directed signalling, and recent studies have provided direct evidence that different agonists stabilise distinct GPCR conformations. This field is rapidly evolving, but a key question is whether signalling bias observed in heterologous cell expression systems can be translated to physiological systems of therapeutic relevance. The paper by Ngala et al. in this issue of the journal addresses the capacity of agonists acting at the β2-adrenoceptor to engender signalling bias in relation to glucose uptake in isolated skeletal muscle, an area of considerable potential interest in targeting insulin-independent pathways for the treatment of type 2 diabetes. The authors show that clenbuterol and BRL37344 have opposite effects on glucose uptake, despite both having agonist actions at β2-adrenoceptors. This study underlines some of the obstacles associated with studies in a complex physiological system but nonetheless highlights the need to consider signalling bias in the relevant target tissue when developing novel drugs.
Stimulation of α1‐adrenoceptors in rat kidney mediates increased inositol phospholipid hydrolysis
Publisher: Wiley
Date: 06-1987
DOI: 10.1111/J.1476-5381.1987.TB10291.X
Abstract: The molecular events which follow activation of alpha 1-adrenoceptors in rat kidney were investigated by measuring inositol phospholipid hydrolysis. Slices were labelled with [3H]-inositol (0.25 microM) and the accumulation of [3H]-inositol phosphates ([3H]-IP's) was measured after stimulation with alpha-adrenoceptor agonists. Phospholipid labelling was both time- and Ca2+-dependent. In kidney, Ca2+ (1 mM) increased the incorporation of [3H]-inositol by 49% and in cerebral cortex reduced it by 46%. Following addition of noradrenaline (NA, 1 mM), accumulation of [3H]-IP's increased linearly for at least 60 min. In Ca2+-free buffers a 2.1 fold increase in [3H]-IP accumulation was observed and further increases in stimulated and control levels were produced in the presence of Ca2+ (2.5 mM). These responses were attenuated by the inclusion of indomethacin (10 microM) and abolished in the presence of EGTA (0.5 mM). Responses to (-)-NA were more than 4 fold higher in the renal cortex than in the medulla. Separation of the IP's which accumulate after alpha-adrenoceptor agonists showed that after 60 min stimulation the major products were glycerophosphoinositol and inositol-phosphate with smaller amounts of inositol-bisphosphate and inositol-trisphosphate. The most effective agonists tested for stimulation of accumulation of [3H]-IP's were (-)-NA greater than phenylephrine greater than methoxamine, (+)-NA. Clonidine and (-)-isoprenaline were ineffective at concentrations up to 100 microM. The order of effectiveness of alpha-adrenoceptor antagonists was prazosin greater than BE2254 greater than phentolamine greater than idazoxan greater than rauwolscine. The results indicate that alpha 1-adrenoceptors in rat kidney are linked to phosphoinositide hydrolysis and that this response is localized mainly to the renal cortex.
THE CHARACTERISTICS OF [3H]-CLONIDINE BINDING TO ANα-ADRENOCEPTOR IN MEMBRANES FROM GUINEA-PIG KIDNEY
Publisher: Wiley
Date: 04-1979
DOI: 10.1111/J.1476-5381.1979.TB07879.X
Abstract: 1. [3H]-clonidine binds to membranes prepared from guinea-pig kidney. 2. At 25 degrees C the binding is rapid and saturable. 3. Scatchard analysis of the binding data showed that the Kd for [3H]-clonidine binding in kidney membranes is 8.54 nM and the density of binding sites 12.5 pmol/g wet wt. tissue. 4. Hill plots of the binding data showed that there were no cooperative site interactions associated with binding. 5. [3H]-clonidine binding could be displaced by drugs, the most potent being drugs with a high affinity for the alpha-adrenoceptor. The neuroleptic drugs (+)-butaclamol, cis-clopenthixol and cis-flupenthixol at high concentration also displaced [3H]-clonidine binding. 6. Drugs acting as agonists or antagonists of beta-adrenoceptors, histamine receptors, acetylcholine receptors as well as prostaglandins E1, E2, F1alpha and F2alpha, angiotensin II, arginine vasopressin, naloxone, nalorphine and pargyline had little effect on binding. 7. It is likely that the binding site labelled by [3H]-clonidine in guinea-pig kidney membranes is an alpha-adrenoceptor similar in some pharmacological aspects to an alpha2-adrenoceptor.
AUTORADIOGRAPHIC ANALYSIS OF (‐)‐[125I]‐CYP BINDING IN MOUSE KIDNEY
Publisher: Wiley
Date: 03-1986
DOI: 10.1111/J.1440-1681.1986.TB00339.X
Abstract: The distribution and binding characteristics of the radioligand (-)-[125I]-cyanopindolol (CYP) have been examined in slide mounted mouse kidney sections, using the technique of in vitro labelling and autoradiography. (-)-[125I]-CYP binding to sections was of high affinity (KD = 55.8 pmol/l, s.e.m. = 8.1, n = 4) to a single population of non-interacting sites (nH = 0.95, s.e.m. = 0.01, Bmax = 0.74 fmol/section, s.e.m. = 0.12, n = 4) and stereoselective with respect to the (-)- and (+)-isomers of both propranolol and pindolol. Autoradiographic studies showed that (-)-[125I]-CYP binding was localized to areas in the renal cortex and medulla. Both cortical and medullary binding were abolished by the inclusion of (-)-propranolol (1 mumol/l) in the incubation medium, whereas (-)-isoprenaline (200 mumol/l) selectively abolished cortical binding. Medullary binding could be prevented by the inclusion of the lipophilic compounds cinanserin (10 mumol/l), haloperidol (10 mumol/l) or phentolamine (10 mumol/l), either alone or together or by washing at 37 degrees C. These results suggest that medullary binding sites are lipid rather than receptor-related. In conclusion, in mouse kidney sections, (-)-[125I]-CYP binds to discrete areas in the cortex and medulla. Cortical binding sites have the molecular characteristics of beta-adrenoceptors while medullary binding sites are lipid-related. Caution should therefore be exercised when defining non-specific binding of lipophilic radioligands. The autoradiographic technique is useful for discriminating between receptor and non-receptor binding sites.
Autoradiographic analysis of receptors on vascular endothelium
Publisher: Elsevier BV
Date: 1987
DOI: 10.1016/0014-2999(87)90128-2
Abstract: Receptor autoradiography was used to examine the distribution of muscarinic cholinoceptors ([3H]QNB), alpha 2-adrenoceptors ([3H]rauwolscine), beta-adrenoceptors ([125I]CYP) and substance P receptors ([125I]BHSP) in rabbit aorta, pulmonary artery, rat aorta, dog aorta, splenic, renal and coronary arteries, bovine aorta and coronary arteries. Muscarinic cholinoceptors and alpha 2-adrenoceptors were not associated with endothelium in any of the blood vessels examined. Substance P receptors were found on endothelium in dog renal but not bovine coronary arteries, and beta-adrenoceptors were found on endothelium in dog coronary arteries but not bovine aorta. The results suggest that endothelium-dependent relaxation can result either from activation of receptors located directly on the endothelial cells or, as is the case for ACh, by an indirect mechanism via activation of receptors located on the vascular smooth muscle.
Densitometric analysis of β1- and β2-adrenoceptors in guinea-pig atrioventricular conducting system
Publisher: Elsevier BV
Date: 04-1990
DOI: 10.1016/0022-2828(90)91483-N
Abstract: Quantitative autoradiography was used to determine the densities of beta 1- and beta 2-adrenoceptors in the atrioventricular conducting system in guinea-pig. (-)[125I]Cyanopindolol (CYP) was used to label beta 1- and beta 2-adrenoceptors in the absence or presence of the beta 1-adrenoceptor selective antagonist CGP 20712A (100 nM) or the beta 2-adrenoceptor selective antagonist ICI 118,551 (70 nM) or the non-selective beta-adrenoceptor antagonist (-)-propranolol (1 microM). Protein in discrete anatomical regions was determined using a densitometric method based on the dye Coomassie brilliant blue G. In the atrioventricular conducting system the proportion of beta 2-adrenoceptors determined by inhibition of total (-)[125I]-CYP binding by CGP 20712A (100 nM) ranged from 32.5% (atrioventricular node) to 48.7% (left bundle branch). In the atrioventricular node (16.8 fmol/mg protein), bundle of His (12.1 fmol/mg protein), right (17.4 fmol/mg protein) and left (21.1 fmol/mg protein) bundle branches and Purkinje cells there was a higher density of beta 2-adrenoceptors than in the interventricular septum (8.4 fmol/mg protein) and right atria (8.3 fmol/mg protein). The medial smooth muscle of the aorta, aortic valve, adventitia of the aorta, nerve tissue, tricuspid and mitral valves contained only beta 2-adrenoceptors. It is speculated that the use of beta-adrenoceptor antagonists to control cardiac arrhythmias involving a defect in conduction in the atrioventricular node should take into consideration both beta 1- and beta 2-adrenoceptors.
Serelaxin-mediated signal transduction in human vascular cells: Bell-shaped concentration-response curves reflect differential coupling to G proteins
Publisher: Wiley
Date: 12-2015
DOI: 10.1111/BPH.12964
Relaxin family peptide receptors in GtoPdb v.2021.3
Publisher: Edinburgh University Library
Date: 02-09-1970
DOI: 10.2218/GTOPDB/F60/2021.3
Abstract: Relaxin family peptide receptors (RXFP, nomenclature as agreed by the NC-IUPHAR Subcommittee on Relaxin family peptide receptors [18, 81]) may be ided into two pairs, RXFP1/2 and RXFP3/4. Endogenous agonists at these receptors are heterodimeric peptide hormones structurally related to insulin: relaxin-1, relaxin, relaxin-3 (also known as INSL7), insulin-like peptide 3 (INSL3) and INSL5. Species homologues of relaxin have distinct pharmacology and relaxin interacts with RXFP1, RXFP2 and RXFP3, whereas mouse and rat relaxin selectively bind to and activate RXFP1 [184]. relaxin-3 is the ligand for RXFP3 but it also binds to RXFP1 and RXFP4 and has differential affinity for RXFP2 between species [183]. INSL5 is the ligand for RXFP4 but is a weak antagonist of RXFP3. relaxin and INSL3 have multiple complex binding interactions with RXFP1 [189] and RXFP2 [91] which direct the N-terminal LDLa modules of the receptors together with a linker domain to act as a tethered ligand to direct receptor signaling [186]. INSL5 and relaxin-3 interact with their receptors using distinct residues in their B-chains for binding, and activation, respectively [225, 104].
Adrenoceptors in GtoPdb v.2021.3
Publisher: Edinburgh University Library
Date: 02-09-2021
Abstract: The nomenclature of the Adrenoceptors has been agreed by the NC-IUPHAR Subcommittee on Adrenoceptors [60, 186]. Adrenoceptors, α1 The three α1-adrenoceptor subtypes α1A, α1B and α1D are activated by the endogenous agonists (-)-adrenaline and (-)-noradrenaline. -(-)phenylephrine, methoxamine and cirazoline are agonists and prazosin and doxazosin antagonists considered selective for α1- relative to α2-adrenoceptors. [3H]prazosin and [125I]HEAT (BE2254) are relatively selective radioligands. S(+)-niguldipine also has high affinity for L-type Ca2+ channels. Fluorescent derivatives of prazosin (Bodipy FLprazosin- QAPB) are used to examine cellular localisation of α1-adrenoceptors. α1-Adrenoceptor agonists are used as nasal decongestants antagonists to treat symptoms of benign prostatic hyperplasia (alfuzosin, doxazosin, terazosin, tamsulosin and silodosin, with the last two compounds being α1A-adrenoceptor selective and claiming to relax bladder neck tone with less hypotension) and to a lesser extent hypertension (doxazosin, terazosin). The α1- and β2-adrenoceptor antagonist carvedilol is used to treat congestive heart failure, although the contribution of α1-adrenoceptor blockade to the therapeutic effect is unclear. Several anti-depressants and anti-psychotic drugs are α1-adrenoceptor antagonists contributing to side effects such as orthostatic hypotension. Adrenoceptors, α2 The three α2-adrenoceptor subtypes α2A, α2B and α2C are activated by (-)-adrenaline and with lower potency by (-)-noradrenaline. brimonidine and talipexole are agonists and rauwolscine and yohimbine antagonists selective for α2- relative to α1-adrenoceptors. [3H]rauwolscine, [3H]brimonidine and [3H]RX821002 are relatively selective radioligands. There are species variations in the pharmacology of the α2A-adrenoceptor. Multiple mutations of α2-adrenoceptors have been described, some associated with alterations in function. Presynaptic α2-adrenoceptors regulate many functions in the nervous system. The α2-adrenoceptor agonists clonidine, guanabenz and brimonidine affect central baroreflex control (hypotension and bradycardia), induce hypnotic effects and analgesia, and modulate seizure activity and platelet aggregation. clonidine is an anti-hypertensive (relatively little used) and counteracts opioid withdrawal. dexmedetomidine (also xylazine) is increasingly used as a sedative and analgesic in human [31] and veterinary medicine and has sympatholytic and anxiolytic properties. The α2-adrenoceptor antagonist mirtazapine is used as an anti-depressant. The α2B subtype appears to be involved in neurotransmission in the spinal cord and α2C in regulating catecholamine release from adrenal chromaffin cells. Although subtype-selective antagonists have been developed, none are used clinically and they remain experimental tools. Adrenoceptors, β The three β-adrenoceptor subtypes β1, β2 and β3 are activated by the endogenous agonists (-)-adrenaline and (-)-noradrenaline. Isoprenaline is selective for β-adrenoceptors relative to α1- and α2-adrenoceptors, while propranolol (pKi 8.2-9.2) and cyanopindolol (pKi 10.0-11.0) are relatively selective antagonists for β1- and β2- relative to β3-adrenoceptors. (-)-noradrenaline, xamoterol and (-)-Ro 363 show selectivity for β1- relative to β2-adrenoceptors. Pharmacological differences exist between human and mouse β3-adrenoceptors, and the 'rodent selective' agonists BRL 37344 and CL316243 have low efficacy at the human β3-adrenoceptor whereas CGP 12177 (low potency) and L 755507 activate human β3-adrenoceptors [88]. β3-Adrenoceptors are resistant to blockade by propranolol, but can be blocked by high concentrations of bupranolol. SR59230A has reasonably high affinity at β3-adrenoceptors, but does not discriminate between the three β- subtypes [320] whereas L-748337 is more selective. [125I]-cyanopindolol, [125I]-hydroxy benzylpindolol and [3H]-alprenolol are high affinity radioligands that label β1- and β2- adrenoceptors and β3-adrenoceptors can be labelled with higher concentrations (nM) of [125I]-cyanopindolol together with β1- and β2-adrenoceptor antagonists. Fluorescent ligands such as BODIPY-TMR-CGP12177 can be used to track β-adrenoceptors at the cellular level [8]. Somewhat selective β1-adrenoceptor agonists (denopamine, dobutamine) are used short term to treat cardiogenic shock but, chronically, reduce survival. β1-Adrenoceptor-preferring antagonists are used to treat cardiac arrhythmias (atenolol, bisoprolol, esmolol) and cardiac failure (metoprolol, nebivolol) but also in combination with other treatments to treat hypertension (atenolol, betaxolol, bisoprolol, metoprolol and nebivolol) [507]. Cardiac failure is also treated with carvedilol that blocks β1- and β2-adrenoceptors, as well as α1-adrenoceptors. Short (salbutamol, terbutaline) and long (formoterol, salmeterol) acting β2-adrenoceptor-selective agonists are powerful bronchodilators used to treat respiratory disorders. Many first generation β-adrenoceptor antagonists (propranolol) block both β1- and β2-adrenoceptors and there are no β2-adrenoceptor-selective antagonists used therapeutically. The β3-adrenoceptor agonist mirabegron is used to control overactive bladder syndrome. There is evidence to suggest that β-adrenoceptor antagonists can reduce metastasis in certain types of cancer [189].
FUNCTION, CHARACTERIZATION AND AUTORADIOGRAPHIC LOCALIZATION AND QUANTITATION OF β‐ADRENOCEPTORS IN CARDIAC TISSUES
Publisher: Wiley
Date: 06-1989
DOI: 10.1111/J.1440-1681.1989.TB01600.X
Abstract: 1. This paper demonstrates the use of organ bath, radioligand binding and autoradiography to detect beta 1- and beta 2-adrenoceptors in human and guinea-pig cardiac tissues. 2. In organ bath experiments, non-selective and beta 1- and beta 2-adrenoceptor selective agonists produced concentration-dependent inotropic responses in human right atrial appendage. Both subtypes mediate inotropic responses. In guinea-pig right atria chronotropic responses were mediated predominantly through beta 1-adrenoceptors. 3. Receptor binding studies using (-)[125I]-cyanopindolol (CYP) and beta 1- and beta 2-adrenoceptor selective antagonists showed that beta 2-adrenoceptors comprised 25% of the total population of beta-adrenoceptors in guinea-pig right atria. In human right atria the proportion is higher (40%). 4. Quantitative autoradiography was used to determine the location and densities of beta 1- and beta 2-adrenoceptors in guinea-pig heart. Both beta 1- and beta 2-adrenoceptors were distributed on myocardium. The atrioventricular conducting system had a higher density of beta 2-adrenoceptors compared with myocardium.
New views of human cardiac β-adrenoceptors
Publisher: Elsevier BV
Date: 05-1989
DOI: 10.1016/0022-2828(89)90791-8
Abstract: Small ubiquitin-related modifiers (SUMOs) regulate erse cellular processes through their covalent attachment to target proteins. Vertebrates express three SUMO paralogs: SUMO-1, SUMO-2, and SUMO-3 (SUMO-2 and SUMO-3 are approximately 96% identical and referred to as SUMO-2/3). SUMO-1 and SUMO-2/3 are conjugated, at least in part, to unique subsets of proteins and thus regulate distinct cellular pathways. However, how different proteins are selectively modified by SUMO-1 and SUMO-2/3 is unknown. We demonstrate that BLM, the RecQ DNA helicase mutated in Bloom syndrome, is preferentially modified by SUMO-2/3 both in vitro and in vivo. Our findings indicate that non-covalent interactions between SUMO and BLM are required for modification at non-consensus sites and that preferential SUMO-2/3 modification is determined by preferential SUMO-2/3 binding. We also present evidence that sumoylation of a C-terminal fragment of HIPK2 is dependent on SUMO binding, indicating that non-covalent interactions between SUMO and target proteins provide a general mechanism for SUMO substrate selection and possible paralog-selective modification.
Characterization of postsynaptic α‐adrenoceptors in rat aortic strips and portal veins
Publisher: Wiley
Date: 07-1983
DOI: 10.1111/J.1476-5381.1983.TB10002.X
Abstract: Postsynaptic alpha-adrenoceptors in rat isolated aortic strips and portal veins have been examined using a number of agonist and antagonist drugs which have varying selectivity for alpha 1- and alpha 2-adrenoceptors. In both tissues (-)-noradrenaline [-)-NA), (-)-adrenaline [-) Adr) (-)-alpha-methyl noradrenaline [-)-alpha-Me-NA) and (-)-phenylephrine [-)-PE) were full agonists, while clonidine, oxymetazoline and (2-(2,6-dichlorophenyl)-5,6-dihydroimidazo(2,1,b) thiazole (44,549) were partial agonists. Guanfacine was a full agonist in aortic strips but only a partial agonist in portal veins. In aortic strips, pA2 values for prazosin and yohimbine were not significantly different using (-)-NA, (-)-PE or guanfacine as the agonist, suggesting a single population of alpha-adrenoceptors. The order of potency of the antagonists, prazosin = 2-(beta-(4-hydroxyphenyl)-ethylaminomethyl)-tetralone (BE2254) greater than phentolamine greater than yohimbine greater than rauwolscine, is indicative of an alpha 1-type of receptor. In portal veins, the order of potency of the antagonists was prazosin greater than BE2254 greater than phentolamine greater than yohimbine greater than rauwolscine, again indicating an alpha 1-type of receptor. The mean pA2 value for yohimbine was not significantly different in either tissue. However, mean pA2 values for prazosin, BE-2254 and phentolamine were approximately one order of magnitude lower in portal veins than in aortic strips, suggesting that the receptors in the two tissues may not be identical.
The relationship between α2-adrenoceptor selectivity and anticonvulsant effect in a series of clonidine-like drugs
Publisher: Elsevier BV
Date: 06-1982
DOI: 10.1016/0006-8993(82)91086-1
Abstract: Clonidine and the 4 clonidine-like drugs: 44-549, lofexidine, guanfacine, and CP-14,304-18, had anticonvulsant activity against pentylenetetrazole-induced convulsions in rats. The magnitude and dose range over which anticonvulsant effects were observed was related to the selectivity of the compounds for alpha 2 and alpha 1 adrenoceptors. Selective alpha 2 adrenoceptor agonists may form a new group of anticonvulsants.
Mouse beta 3a- and beta 3b-adrenoceptors expressed in Chinese hamster ovary cells display identical pharmacology but utilize distinct signalling pathways.
Publisher: Wiley
Date: 04-2002
The beta3-adrenoceptor agonist 4-[[(Hexylamino)carbonyl]amino]-N-[4-[2-[[(2S)-2-hydroxy-3-(4-hydroxyphenoxy)propyl]amino]ethyl]-phenyl]-benzenesulfonamide (L755507) and antagonist (S)-N-[4-[2-[[3-[3-(acetamidomethyl)phenoxy]-2-hydroxypropyl]amino]-ethyl]phenyl]benzenesulfonamide (L748337) activate different signaling pathways in Chinese hamster ovary-K1 cells stably expressing the human beta3-adrenoceptor.
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 06-08-2008
Abstract: This study identifies signaling pathways activated by the beta(2)-/beta(3)-adrenoceptor (AR) agonist zinterol, the selective beta(3)-AR agonist L755507, and the selective beta(3)-AR antagonist L748337 in CHO-K1 cells expressing human beta(3)-adrenoceptors. Zinterol and L755507 caused a robust concentration-dependent increase in cAMP accumulation (pEC(50) values of 8.5 and 12.3, respectively), whereas L748337 had low efficacy. Maximal cAMP accumulation with zinterol and L755507 was increased after pretreatment with pertussis toxin, indicating that the human beta(3)-AR couples to G(i) and to G(s). In contrast to cAMP, zinterol, L755507 and L748337 increased phosphorylation of extracellular signal-regulated kinase 1/2 (Erk1/2) with very high potency (pEC(50) values of 10.9, 11.7, and 11.6). These compounds also stimulated phosphorylation of p38 mitogen-activated protein kinase (MAPK) but with much lower potency than Erk1/2 (pEC(50) values of 5.9, 5.5, and 5.7, respectively). Pertussis toxin completely blocked Erk1/2 and p38 MAPK phosphorylation in response to L748337, demonstrating a requirement for G(i/o) coupling, whereas L755507-stimulated p38 MAPK phosphorylation was not inhibited by pertussis toxin, and Erk1/2 phosphorylation was inhibited by only 30%. We found that high levels of cAMP interfered with agonist-activated p38 MAPK phosphorylation. L748337 increased extracellular acidification rate (ECAR) in the cytosensor microphysiometer with efficacy similar to zinterol and L755507, albeit with lower potency (pEC(50) value of 7.2 compared with zinterol, 8.1, and L755507, 8.6). The ECAR response to L748337 was largely via activation of p38 MAPK, demonstrated by 65% inhibition with 4-[4-(4-fluorophenyl)-1-(3-phenylpropyl)-5-(4-pyridinyl)-1H-imidazol-2-yl]-3-butyn-1-ol (RWJ67657). We conclude that the beta(3)-AR agonist L755507 couples to both G(s) and G(i) to activate adenylate cyclase and MAPK signaling, whereas the beta(3)-AR antagonist L748337 couples predominantly to G(i) to activate MAPK signaling.
Ligand-directed signaling at the beta3-adrenoceptor produced by 3-(2-Ethylphenoxy)-1-[(1,S)-1,2,3,4-tetrahydronapth-1-ylamino]-2S-2-propanol oxalate (SR59230A) relative to receptor agonists.
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 23-08-2007
Abstract: This study examines signaling pathways activated by the mouse beta(3)-adrenoceptor (AR) expressed in Chinese hamster ovary cells at high (CHObeta(3)H) or low (CHObeta(3)L) levels. Functional responses included extracellular acidification rate (ECAR), cAMP accumulation, and p38 mitogen-activated protein kinase (MAPK) or extracellular signal-regulated protein kinase 1/2 (Erk1/2) phosphorylation. (-)-Isoproterenol and the beta(3)-AR agonist (R, R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino]-propyl]1,3-benzodioxole-2,2-decarboxylate (CL316243) caused concentration-dependent increases in cAMP accumulation and ECAR in CHObeta(3)H and CHObeta(3)L cells. For cAMP accumulation, the beta(3)-AR ligand SR59230A was a partial agonist in CHObeta(3)H and an antagonist in CHObeta(3)L cells but for ECAR was an agonist at both expression levels. This suggested that SR59230A, which is normally regarded as an antagonist, can selectively activate pathways leading to ECAR. Examination of the pathways stimulated by (-)-isoproterenol, CL316243, and SR59230A for both ECAR and cAMP accumulation suggested that the cAMP pathway predominates in CHObeta(3)H cells, whereas p38 MAPK is a major contributor to ECAR in CHObeta(3)L cells and was the sole contributor to responses to SR59230A. Western blots of p38 MAPK and Erk1/2 phosphorylation confirmed that MAPKs are activated in CHObeta(3)H and CHObeta(3)L cells by CL316243 and SR59230A but that SR59230A has much higher efficacy. In addition, p38 MAPK phosphorylation displayed differences in drug potency and efficacy between CHObeta(3)H and CHObeta(3)L cells related to inhibition of the response by cAMP. Thus, CL316243 and SR59230A display reversed orders of efficacy for cAMP accumulation compared with Erk1/2 and p38 MAPK phosphorylation, providing a strong indication of ligand-directed signaling.
Molecular pharmacology of GPCRs
Publisher: Wiley
Date: 09-10-2018
DOI: 10.1111/BPH.14474
Effects of yohimbine stereoisomers on contractions of rat aortic strips produced by agonists with different selectivity for α1-and α2-adrenoceptors
Publisher: Elsevier BV
Date: 12-1983
DOI: 10.1016/0014-2999(83)90533-2
Abstract: Three stereoisomers of yohimbine (corynanthine, rauwolscine and yohimbine) have been used to characterize alpha-adrenoceptors in rat aortic strips. pA2 values for each antagonist were calculated using 3 different agonists ((-)-noradrenaline, (-)-phenylephrine and guanfacine) which possess varying affinities for alpha 1 and alpha 2 receptors. Mean pA2 values were not significantly different irrespective of the agonist used and the order of the potency was corynanthine greater than yohimbine greater than rauwolscine. The results are consistent with the presence of alpha 1-adrenoceptors in rat aorta.
Roles of the receptor, the ligand, and the cell in the signal transduction pathways utilized by the relaxin family peptide receptors 1-3
Publisher: Wiley
Date: 04-2009
Relaxin family peptide receptors - Former orphans reunite with their parent ligands to activate multiple signalling pathways
Publisher: Wiley
Date: 03-2007
The C-terminus of the B-chain of human insulin-like peptide 5 is critical for cognate RXFP4 receptor activity.
Publisher: Springer Science and Business Media LLC
Date: 11-12-2015
DOI: 10.1007/S00726-015-2144-5
Abstract: Insulin-like peptide 5 (INSL5) is an orexigenic peptide hormone belonging to the relaxin family of peptides. It is expressed primarily in the L-cells of the colon and has a postulated key role in regulating food intake. Its G protein-coupled receptor, RXFP4, is a potential drug target for treating obesity and anorexia. We studied the effect of modification of the C-terminus of the A and B-chains of human INSL5 on RXFP4 binding and activation. Three variants of human INSL5 were prepared using solid phase peptide synthesis and subsequent sequential regioselective disulfide bond formation. The peptides were synthesized as C-terminal acids (both A- and B-chains with free C-termini, i.e., the native form), amides (both chains as the C-terminal amide) and one analog with the C-terminus of its A-chain as the amide and the C-terminus of the B-chain as the acid. The results showed that C-terminus of the B-chain is more important than that of the A-chain for RXFP4 binding and activity. Amidation of the A-chain C-terminus does not have any effect on the INSL5 activity. The difference in RXFP4 binding and activation between the three peptides is believed to be due to electrostatic interaction of the free carboxylate of INSL5 with a positively charged residue (s), either situated within the INSL5 molecule itself or in the receptor extracellular loops.
Autoradiographic localization of β-adrenoceptors in rat kidney
Publisher: Elsevier BV
Date: 07-1983
DOI: 10.1016/0014-2999(83)90484-3
Abstract: The beta-adrenoceptor antagonist radioligand [125I]cyanopindolol (CYP) has been used to localize beta-adrenoceptors in rat kidney sections. [125I]CYP bound with high affinity to sites in rat kidney sections having the recognition characteristics of beta-adrenoceptors. Autoradiographic studies combined with histochemical techniques demonstrated that the beta-adrenoceptors were primarily located on renal glomeruli, distal and cortical collecting tubules rather than on proximal tubules or vascular elements.
Intracerebroventricular administration of the β3-adrenoceptor agonist CL 316243 causes Fos immunoreactivity in discrete regions of rat hypothalamus
Publisher: Elsevier BV
Date: 09-2000
DOI: 10.1016/S0304-3940(00)01359-8
Abstract: Intracerebroventricular (i.c.v.) administration of the beta(3)-AR agonist BRL37344 causes dose dependent decreases in food intake in rats suggesting a role for beta(3)-AR in the central control of feeding. We have conducted experiments investigating the effects of i.c.v. administration of the selective beta(3)-AR agonist CL316243 on Fos expression to determine whether beta(3)-AR stimulation affects neurones within specific brain nuclei. Significantly higher numbers of Fos positive cells were found in the rats treated i.c.v. with CL316243 compared with control rats in the paraventricular hypothalamus, lateral hypothalamic area, ventromedial hypothalamic nucleus and dorsal hypothalamic area. Pre-treatment with the selective beta(3)-AR antagonist SR59230A resulted in a significant decrease in the number of Fos positive cells in all those areas compared with rats treated with CL316243 alone. These experiments demonstrate that i.c.v. administration of selective beta(3)-AR agonist causes neuronal activation in hypothalamic areas important in the central regulation of appetite via a beta(3)-AR mediated effect.
Enhanced serelaxin signalling in co-cultures of human primary endothelial and smooth muscle cells.
Publisher: Wiley
Date: 15-01-2016
DOI: 10.1111/BPH.13371
Expression of β3‐adrenoceptor mRNA in rat brain
Publisher: Wiley
Date: 11-1995
DOI: 10.1111/J.1476-5381.1995.TB17205.X
Abstract: The reverse transcription olymerase chain reaction was used to demonstrate beta 3-adrenoceptor mRNA in rat brain regions. Levels were highest in hippoc us, cerebral cortex and striatum and lower in hypothalamus, brainstem and cerebellum.
Divergent effects of strontium and calcium‐sensing receptor positive allosteric modulators (calcimimetics) on human osteoclast activity
Publisher: Wiley
Date: 03-06-2018
DOI: 10.1111/BPH.14344
Stimulation of α1‐adrenoceptors inhibits memory consolidation in the chick
Publisher: Wiley
Date: 10-2001
DOI: 10.1046/J.0953-816X.2001.01742.X
Abstract: Investigation of the effects of the different adrenoceptor (AR) subtypes in memory formation may reveal discrete actions of noradrenaline in memory modulation and storage mediated through particular AR subtypes. Noradrenaline injected intracerebrally in the chick produced biphasic effects on memory consolidation with enhancement at low doses and inhibition at high doses. We have previously shown that the enhancement by the lower doses of noradrenaline is attributable to actions at beta2- and beta3-adrenoceptors, whereas the inhibitory effect of higher doses is attributable to alpha1-adrenoceptors. The present studies show that the inhibition of memory by high doses of noradrenaline is mimicked by the alpha1-AR agonist methoxamine, and the dose-response curve is shifted to the right by pretreatment with the alpha1-AR antagonist prazosin. alpha1-ARs may play a critical role in memory formation in highly stressful situations, when noradrenaline levels are high in particular brain regions. It is not known where the alpha1-ARs responsible for the effect on memory are localized. alpha1-ARs are found on neurons and astrocytes and in the cerebral vasculature and therefore the action of high doses of noradrenaline via alpha1-AR agonists could be via an action at any of these sites. Activation of alpha1-adrenoceptors in the intermediate hyperstriatum ventrale in the chick forebrain by the alpha1 adrenoceptor agonist methoxamine inhibits the consolidation of memory. Because the same effect is produced by high levels of noradrenaline, it is likely that stimulation of alpha1-ARs is the mechanism underlying this effect.
Signalling profiles of H 3 relaxin, H 2 relaxin and R 3(BΔ 23–27)R /I 5 acting at the relaxin family peptide receptor 3 (RXFP 3)
Publisher: Wiley
Date: 15-05-2014
DOI: 10.1111/BPH.12623
The effect of monoamine oxidase inhibitors on the rectal temperature of the rat
Publisher: Oxford University Press (OUP)
Date: 05-1974
DOI: 10.1111/J.2042-7158.1974.TB09284.X
Abstract: The monoamine oxidase (MAO) inhibitors, clorgyline, harmaline, nialamide, phenelzine and tranylcypromine, injected intraperitoneally into conscious unrestrained rats produced hypothermia. When clorgyline and tranylcypromine were compared, the latter produced a larger degree of hypothermia in spite of the fact that both drugs almost completely inhibited liver and hypothalamic MAO. Hypothermia produced by tranylcypromine, but not that produced by clorgyline, was attenuated by prior administration of haloperidol which indicated that it was partly mediated by a dopaminergic mechanism. In addition, tranylcypromine, but not clorgyline, inhibited uptake of (–)-noradrenaline into rat hearts. Hypoglycaemia was not involved in the hypothermia produced by these MAO inhibitors in rats.
Characterization of propranolol‐resistant (−)‐[125I]‐cyanopindolol binding sites in rat soleus muscle
Publisher: Wiley
Date: 06-1993
DOI: 10.1111/J.1476-5381.1993.TB13576.X
Abstract: 1. The characteristics of a propranolol-resistant (-)-[125I]-cyanopindolol (CYP) binding site in rat soleus muscle were determined. 2. Saturation studies performed on homogenates of rat soleus muscle showed two phases of (-)-[125I]-CYP binding, a high affinity site (KD1 30.5 +/- 16.3 pM, Bmax 9.4 +/- 1.38 fmol mg-1 protein) and a lower affinity site (KD2 522.5 +/- 29.1 pM, Bmax 62.19 +/- 11.76 fmol mg-1 protein, n = 4). 3. In rat soleus muscle homogenates labelled with (-)-[125I]-CYP (500 pM), (-)-propranolol competition curves were biphasic with pKD values of 8.30 +/- 0.19, and 5.33 +/- 0.08, n = 7. 4. Competition between (-)-[125I]-CYP (500 pM) and (+/-)-tertatolol, (+/-)-nadolol, (+/-)-alprenolol, (+/-)-CYP, and (-) and (+)-pindolol showed that these compounds competed for binding at the propranolol-resistant site with affinities lower than those displayed at typical beta-adrenoceptors. The atypical beta-adrenoceptor agonists BRL 37344, SR58611A and ICI D7114 and the partial agonist (+/-)-CGP 12177 also competed for (-)-[125I]-CYP binding. 5. Stereoselectivity was demonstrated for the stereoisomers of alprenolol and tertalolol. The (-)-isomers of alprenolol and tertalolol had higher affinity than their corresponding (+)-isomers (3.1 and 2.6 fold respectively). These low stereoselectivity values are a characteristic of atypical beta-adrenoceptors. 6. The beta-adrenoceptor agonists, (-)-adrenaline, (-)-isoprenaline and (-)-noradrenaline, all showed lower affinity than the atypical beta-adrenoceptor agonists and competition curves appeared biphasic in nature. 7. These results confirm the presence of a propranolol-resistant (- )-[125I]-CYP binding site in rat soleus muscle. The affinities of the tested compounds at the propranolol-resistant (- )-[125I]-CYP binding site show similarities to their affinities at 'atypical' beta-adrenoceptors in adipocytes and gastrointestinal tissues and at the cloned beta 3-adrenoceptor.
Factors influencing biased agonism in recombinant cells expressing the human α1A‐adrenoceptor
Publisher: Wiley
Date: 10-06-2017
DOI: 10.1111/BPH.13837
Autoradiographic localization of β‐adrenoceptor subtypes in guinea‐pig kidney
Publisher: Wiley
Date: 06-1985
DOI: 10.1111/J.1476-5381.1985.TB08867.X
Abstract: The distribution of beta-adrenoceptor subtypes in slide-mounted sections of guinea-pig kidney has been examined by the technique of in vitro labelling combined with autoradiography. Binding of (-)-[125I]-cyanopindolol (Cyp) to kidney sections equilibrated and dissociated slowly, was saturable and stereoselective with respect to the isomers of propranolol and pindolol. These characteristics were appropriate for binding to beta-adrenoceptors. Delineation of beta-adrenoceptor subtypes was achieved by use of betaxolol (beta 1-adrenoceptors) and ICI 118,551 (beta 2-adrenoceptors) and computer assisted curve fitting techniques. Both beta 1- and beta 2-adrenoceptors were present in the proportions 1:2. 3H-Ultrofilm images of (-)-[125I]-Cyp binding to guinea-pig kidney sections showed localized patches of binding in the cortex and concentrated binding in the outer stripe of the medulla. Cortical receptors were of the beta 1 subtype and those associated with the outer stripe of the medulla were of the beta 2-adrenoceptor subtype. beta 1-Adrenoceptors were concentrated over glomeruli and beta 2-adrenoceptors over the straight portion of the proximal tubule.
Excitatory amino acid projections to the periaqueductal gray in the rat: A retrograde transport study utilizing d[3H]aspartate and [3H]GABA
Publisher: Elsevier BV
Date: 1990
DOI: 10.1016/0306-4522(90)90310-Z
Abstract: The afferents to the periaqueductal gray utilizing excitatory amino acid transmitters have been described in rat brain by autoradiography following microinfusion and retrograde transport of D[3H]aspartate. Parallel experiments employing injections of [3H]GABA established that the retrograde labelling found with D[3H]aspartate was transmitter-selective. Following infusion of D[3H]aspartate, perikaryal labelling was found in nine subcortical areas, particularly infralimbic and cingulate cortices, with a predominance of ipsilateral labelled perikarya. Heaviest cortical labelling was localized in perirhinal cortex, in an extensive band of cells adjoining the rhinal sulcus. The hypothalamus contained the heaviest perikaryal labelling within brain: D[3H]aspartate labelled cells in 11 hypothalamic and mammillary nuclei. Intense bilateral labelling was obtained in ventromedial hypothalamus, although the number of perikarya was lower contralaterally. D[3H]Aspartate also produced heavy ipsilateral labelling of perikarya in posterior hypothalamus. Labelling patterns in cortex and hypothalamus were precise and topographic, and [3H]GABA never labelled cells in these regions. Other telencephalic and diencephalic areas containing prominent, retrogradely labelled cells were the lateral septum, amygdala, zona incerta and lateral habenula. The relative density of labelled cells in mesencephalic areas was much lower than that found in cortex and hypothalamus, although D[3H]aspartate labelled a moderate number of perikarya in the inferior colliculus and cuneiform nucleus. A smaller number of heavily labelled cells was found in the parabrachial nuclei, Kolliker-Fuse nucleus and laterodorsal tegmental nucleus. Only occasional labelled perikarya were observed in the myencephalon. Low densities of labelled cells were found after the injection of [3H]GABA into the periaqueductal gray, and the only regions in which a small number of perikarya were labelled by both [3H]GABA and D[3H]aspartate were the dorsal raphe and parabrachial nuclei. Overall, the retrograde transport of D[3H]aspartate revealed a complex topographic and convergent network of afferent pathways to the periaqueductal gray likely to utilize an excitatory amino acid transmitter. Our findings confirm the selectivity of this neurochemical mapping technique and provide evidence that hypothalamic, habenular, subthalamic and cuneiform afferents to the periaqueductal gray utilize an acidic amino acid as their transmitter. They also confirm that corticofugal afferents to periaqueductal gray utilize an excitatory amino acid.
The actions of relaxin family peptides on signal transduction pathways activated by the relaxin family peptide receptor RXFP4.
Publisher: Springer Science and Business Media LLC
Date: 26-11-2016
DOI: 10.1007/S00210-016-1321-8
Abstract: The relaxin family peptide receptor 4 (RXFP4) is a G protein-coupled receptor (GPCR) expressed in the colorectum with emerging roles in metabolism and appetite regulation. It is activated by its cognate ligand insulin-like peptide 5 (INSL5) that is expressed in enteroendocrine L cells in the gut. Whether other evolutionarily related peptides such as relaxin-2, relaxin-3, or INSL3 activate RXFP4 signal transduction mechanisms with a pattern similar to or distinct from INSL5 is still unclear. In this study, we compare the signaling pathways activated by various relaxin family peptides to INSL5. We found that, like INSL5, relaxin-3 activated ERK1/2, p38MAPK, Akt, and S6RP phosphorylations leading to increased cell proliferation and also caused GRK and β-arrestin-mediated receptor internalization. Interestingly, relaxin-3 was slightly more potent than INSL5 in ERK1/2 and Akt phosphorylations, but both peptides were almost equipotent in adenylyl cyclase inhibition, S6RP phosphorylation, and cell proliferation. In addition, relaxin-3 showed greater efficacy only in Akt phosphorylation but not in the other pathways investigated. In contrast, no signaling activity or receptor internalization mechanisms were observed following relaxin-2 and INSL3. In conclusion, relaxin-3 is a high-efficacy agonist at RXFP4 with a comparable signal transduction profile to INSL5.
Role of β-adrenoceptors in the anticonvulsant effect of propranolol on leptazol-induced convulsions in rats
Publisher: Oxford University Press (OUP)
Date: 02-1982
DOI: 10.1111/J.2042-7158.1982.TB04202.X
Abstract: Signal transducer and activator of transcription 3 (STAT3) signaling plays critical roles in regulating skeletal muscle mass, repair, and diseases. In this review, we discuss the upstream activators of STAT3 in skeletal muscles, with a focus on interleukin 6 (IL6) and transforming growth factor beta 1 (TGF-β1). We will also discuss the double-edged effect of STAT3 activation in the muscles, including the role of STAT3 signaling in muscle hypertrophy induced by exercise training or muscle wasting in cachectic diseases and muscular dystrophies. STAT3 is a critical regulator of satellite cell self-renewal after muscle injury. STAT3 knock out affects satellite cell myogenic progression by impairing proliferation and inducing premature differentiation. Recent studies in STAT3 signaling demonstrated its direct role in controlling myogenic capacity of myoblasts and satellite cells, as well as the potential benefit in using STAT3 inhibitors to treat muscle diseases. However, prolonged STAT3 activation in muscles has been shown to be responsible for muscle wasting by activating protein degradation pathways. It is important to balance the extent of STAT3 activation and the duration and location (cell types) of the STAT3 signaling when developing therapeutic interventions. STAT3 signaling in other tissues and organs that can directly or indirectly affects skeletal muscle health are also discussed.
Role of adrenoceptor subtypes in memory consolidation
Publisher: Elsevier BV
Date: 08-2002
DOI: 10.1016/S0301-0082(02)00023-0
Abstract: Noradrenaline release in areas within the forebrain occurs following activation of noradrenergic cells in the locus coeruleus (LoC). Release of noradrenaline by attentional/arousal/vigilance factors appears to be essential for learning and is responsible for the consolidation of memory. Noradrenaline can activate any of nine different adrenoceptor (AR) subtypes in the brain and selectivity of action may be achieved by the spatial location and relative density of the AR subtypes, by different affinities of the different subtypes and by temporal selectivity in terms of when the different ARs are activated in the memory formation process. This review examines the use of selective agonists and antagonists to determine the roles of the AR subtypes in the one-trial discriminated avoidance learning paradigm in the chick. A model is developed that integrates noradrenergic activity in basal ganglia (lobus parolfactorius (LPO)) and association cortex (intermediate medial hyperstriatum ventrale (IMHV)) leading to the consolidation of memory 30 min after training. There is evidence that beta(2)- and beta(3)-ARs are important in the association area but require input from alpha(2)-AR stimulated activity in the basal ganglia for consolidation. On the other hand, alpha(1)-AR activation in the IMHV is inhibitory and prevents consolidation. While there is no role for beta(1)-ARs in memory consolidation, they play a role in short-term memory (STM). The use of the precocial chick has clear advantages in having a temporally discrete learning task which allows for discrimination memory and whose development can be followed at discrete intervals after learning. These studies reveal clear roles for AR subtypes in the formation and consolidation of memory in the chick, which have allowed the development of a model that can now be tested in mammalian systems.
The Effects of the β3-Adrenoceptor Agonist BRL 35135 on UCP Isoform mRNA Expression
Publisher: Elsevier BV
Date: 11-1998
Abstract: The mitochondrial uncoupling protein UCP-1 uncouples respiration from ATP synthesis in brown adipose tissue (BAT) and thus energy is dissipated as heat. Recently two further isoforms have been identified which may play a similar role in other tissues. We have determined the effects of the rodent-selective beta3-adrenoceptor (beta3-AR) agonist BRL 35135, on beta3-AR and UCP mRNA levels in tissues from lean and obese (fa/fa) Zucker rats. beta3-AR mRNA levels were reduced in fa/fa white (WAT) and brown (BAT) adipose tissue relative to levels in lean littermates. BRL 35135 treatment increased expression levels of beta3-AR mRNA in both genotypes. UCP-2 and UCP-3 mRNA levels in BAT, WAT and skeletal muscle were reduced by 2-3 fold in the fa/fa rats relative to the lean rats. We confirm that BRL 35135 increases BAT UCP-1 mRNA in lean rats, and find that BAT UCP-3 mRNA was reduced 3.2 fold, with no changes in UCP-2 expression. In WAT BRL 35135 increased UCP-2 and UCP-3 expression 2-3 fold in both lean and fa/fa rats. In lean rats, skeletal muscle UCP-3 mRNA was increased 2.3 fold by BRL 35135 whereas UCP-2 was reduced by 2.2 fold. BRL 35135 had no effects on UCP-2 and UCP-3 expression in skeletal muscle of the fa/fa rats. Our results demonstrate that mechanisms regulating UCP isoform synthesis in fa/fa rats are impaired and that WAT could be involved in the thermogenic response of BRL 35135.
Themed section: molecular pharmacology of GPCRs
Publisher: Wiley
Date: 22-02-2012
Inhibition by cAMP of the phosphoinositide response to α1-adrenoceptor stimulation in rat kidney
Publisher: Elsevier BV
Date: 04-1988
DOI: 10.1016/0014-2999(88)90124-0
Abstract: The effect of increasing intracellular levels of cAMP has been investigated on the PI response to stimulation of alpha 1-adrenoceptors in rat kidney. Stimulation of adenylate cyclase with forskolin or incubation with dibutyryl cAMP (dcAMP) inhibited noradrenaline (NA)-stimulated [3H]inositol phosphate (IP) accumulation. Forskolin did not alter the EC50 to NA. No effect on NA-stimulated [3H]IP accumulation was seen with dibutyryl cGMP (dcGMP). The results suggest that hormones which produce alterations in cAMP levels influence alpha 1-adrenoceptor-mediated responses.
Evidence for pleiotropic signaling at the mouse beta3-adrenoceptor revealed by SR59230A [3-(2-Ethylphenoxy)-1-[(1,S)-1,2,3,4-tetrahydronapth-1-ylamino]-2S-2-propanol oxalate].
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 12-2005
Abstract: This study examines the action of the beta(3)-adrenoceptor antagonist SR59230A [3-(2-ethylphenoxy)-1-[(1,S)-1,2,3,4-tetrahydronapth-1-ylamino]-2S-2-propanoloxalate] at cloned mouse beta(3)-adrenoceptors expressed in Chinese hamster ovary cells (CHO-K1-beta(3)) or endogenously expressed in 3T3-F442A adipocytes or ileum. SR59230A displayed partial agonist properties compared with the beta(3)-adrenoceptor agonist CL316243 [(R,R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino]-propyl]1,3-benzodioxole-2,2-dicarboxylate] in CHO-K1-beta(3) with the intrinsic activity increasing with the level of receptor expression. Functional affinity values for SR59230A at each level of receptor expression were in agreement with pK(I) values determined by binding. In cytosensor microphysiometer studies, SR59230A was a full agonist for increases in extracellular acidification rates (ECARs) at all levels of receptor expression, and antagonist actions were measurable only in medium- or low-expressing cells. In 3T3-F442A adipocytes, SR59230A antagonized CL316243-mediated increases of cAMP and had no agonist actions. However, in the cytosensor micro-physiometer, SR59230A (acting via beta(3)-adrenoceptors) was an agonist with an intrinsic activity greater than CL316243. In mouse ileum, SR59230A relaxed smooth muscle, although concentration-response curves were biphasic. Relaxant effects were produced by concentrations that did not affect cAMP levels. Differences in tissue responses to SR59230A were not caused by major differences in expression of Galphas. ECAR responses were not affected by pretreatment of cells with pertussis toxin, indicating that signaling did not involve Gi. Therefore, SR59230A displays agonist and antagonist actions at the mouse beta(3)-adrenoceptor. Because SR59230A only antagonized accumulation of cAMP in 3T3-F442A adipocytes yet in the same cells was an agonist for ECAR, cAMP-independent signaling pathways must mediate part of the agonist actions in the microphysiometer.
AUTORADIOGRAPHIC LOCALIZATION OF RECEPTORS IN THE MAMMALIAN CARDIOVASCULAR SYSTEM
Publisher: Wiley
Date: 05-1987
DOI: 10.1111/J.1440-1681.1987.TB00995.X
Abstract: 1. Autoradiographic techniques have been used to examine the location of beta-adrenoceptors in the heart and beta-adrenoceptors, substance P receptors and muscarinic cholinoceptors in blood vessels. 2. Both beta 1-adrenoceptors and beta 2-adrenoceptors were present in guinea-pig and human heart, on the myocardium and associated with the cardiac nerves and blood vessels. 3. Nerves on the vasculature and vascular smooth muscle contained beta-adrenoceptors and muscarinic cholinoceptors. 4. Receptors for substance P and beta-adrenoceptors, but not muscarinic cholinoceptors were present on endothelial cells.
The role of the sympathetic nervous system in the regulation of leptin synthesis in C57BL/6 mice
Publisher: Wiley
Date: 12-02-1999
DOI: 10.1016/S0014-5793(99)00049-6
Abstract: The objectives of this study were to determine whether leptin synthesis is regulated by the sympathetic nervous system and if so whether beta-adrenergic receptors mediate this effect. We show that sympathetic blockade by reserpine increases leptin mRNA levels in brown but not white adipose tissue, while acute cold-exposure decreases leptin expression 10-fold in brown adipose tissue and 2-fold in white adipose tissue. The cold-induced reduction in leptin mRNA can be prevented by a combination of propranolol and SR 59230A but not by either antagonist alone, indicating that beta3-adrenergic receptors and classical beta1/beta2-adrenergic receptors both mediate responses to sympathetic stimulation. Circulating leptin levels reflect synthesis in white adipose tissue but not in brown adipose tissue.
Relaxin family peptide receptor (RXFP1) coupling to Gαi3, involves the C-terminal Arg752 and localization within membrane raft microdomains
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 24-11-2009
Abstract: The relaxin family peptide receptors (RXFP) 1 and 2 are targets for the relaxin family peptides relaxin and insulin-like peptide 3 (INSL3), respectively. Although both receptors and peptides share a high degree of sequence identity, the cAMP signaling pathways activated by the two systems are quite distinct. Relaxin activation of RXFP1 initially results in accumulation of cAMP via G(alpha)(s), but this is modulated by inhibition of cAMP through G(alpha)(oB). Over time, RXFP1 recruits coupling to G(alpha)(i3), causing additional cAMP accumulation via a G(alpha)(i3)-Gbetagamma-phosphoinositide 3-kinase (PI3K)-protein kinase C (PKC)zeta pathway. In contrast, INSL3 activation of RXFP2 results in accumulation of cAMP only via G(alpha)(s), modulated by cAMP inhibition through G(alpha)(oB). Thus, the aim of this study was to identify the cause of differential G-protein coupling between these highly similar receptors. Construction of chimeric receptors revealed that G(alpha)(i3) coupling is dependent upon the transmembrane region of RXFP1 and independent of the receptor ectodomain or ligand bound. Generation of C-terminal truncated receptors identified the terminal 10 amino acids of the RXFP1 C terminus as essential for G(alpha)(i3) signaling, and point mutations revealed an obligatory role for Arg(752). RXFP1-mediated G(alpha)(i3), but not G(alpha)(s) or G(alpha)(oB), signaling was also found to be dependent upon membrane rafts, and RXFP1 coupled to G(alpha)(i3) after only 3 min of receptor stimulation. Therefore, RXFP1 coupling to the G(alpha)(i3)-Gbetagamma-PI3K-PKCzeta pathway requires the terminal 10 amino acids of the RXFP1 C terminus and membrane raft localization, and the observed delay in this pathway occurs downstream of G(alpha)(i3).
Erratum to “effects of glucose and 2-deoxyglucose on memory formation in the chick: interaction with β3-adrenoceptor agonists” [neuroscience 114 (1) 69–79]☆
Publisher: Elsevier BV
Date: 04-2003
Enhancement of memory consolidation in chicks by β3-adrenoceptor agonists
Publisher: Elsevier BV
Date: 02-2001
DOI: 10.1016/S0014-2999(01)00757-9
Abstract: The effects of intracranial injection of three beta(3)-adrenoceptor agonists, sodium-4-[-2[-2-hydroxy-2-(-3-chloro-phenyl)ethylamino] propyl]phenoxyacetate (BRL 37344), 2-hydroxy-5(2-((2-hydroxy-3-(4-((1-methyl-4-trifluoromethyl)1H-imidazole-2-yl)-phenoxy)propyl)amino)ethoxy)-benzamide monomethane sulfonate) (+/-)-CGP12177A) and the pro-drug RS-N-(7-carbethoxymethoxyl 1,2,3,4-tetrahydronaphth-2-yl)-2 hydroxy 2-(3-chlorophenyl)ethanamine (SR58611A), were examined on reinforcement of memory in day-old chicks. BRL37344 and CGP12177 facilitated memory, whereas SR58611A had no effect. The dose-response relationships of the beta(3)-adrenoceptor agonists were challenged with the selective beta(3)-adrenoceptor antagonist 3-(2-ethylphenoxy)-1-[(1S)-1,2,3,4-tetrahydronapth-1-ylamino]-2S-2-propanol oxalate (SR59230A) or the beta(2)-adrenoceptor antagonist (-)propranolol. BRL 37344 appeared to act predominantly at beta(3)-adrenoceptors at low doses and at beta(2)-adrenoceptors at higher doses. Facilitation of labile into long-term storage by beta(3)-adrenoceptor agonists appears to be a class action of these drugs.
Persistent β-adrenoceptor blockade with alkylating pindolol (BIM) in guinea-pig left atria and trachea
Publisher: Elsevier BV
Date: 10-1988
DOI: 10.1016/0006-2952(88)90390-5
Abstract: The actions of alkylating pindolol (N8-bromoacetyl-N1-3'-(4-indolyloxy)-2'-hydroxypropyl[z]-1,8- diamino-p-menthane BIM) have been examined on beta-adrenoceptors in guinea-pig left atria and trachea. In organ bath experiments, addition of BIM (greater than or equal to 0.1 microM), followed by washout, produced concentration-dependent rightward shifts of the dose-response curve to cumulative additions of (-)-isoprenaline and oxymethylene-isoprenaline and reductions in the maximal response. The "apparent" pA2 value for BIM was 9.23 +/- 0.20 (slope = 0.98 +/- 0.20). Changes in the maximal density of beta-adrenoceptor binding sites were determined in guinea-pig left atrial membranes using [125I]-cyanopindolol. BIM (0.1, 1.0 and 10 microM) produced 14, 23 and 41% reductions in Bmax with no change in KD. The binding of [125I]-BIM to guinea-pig left atrial membranes had a high non-specific binding component and a pseudo-Hill coefficient less than unity. The "apparent" KD value of [125I]-BIM at beta-adrenoceptor binding sites was 85.7 +/- 57.9 pM.
Pharmacological insights into safety and efficacy determinants for the development of adenosine receptor biased agonists in the treatment of heart failure
Publisher: Cold Spring Harbor Laboratory
Date: 23-07-2020
DOI: 10.1101/2020.07.22.215509
Abstract: Adenosine A 1 receptors (A 1 R) are a potential target for cardiac injury treatment due to their cardioprotective/antihypertrophic actions, but drug development has been h ered by on-target side effects such as bradycardia and altered renal haemodynamics. Biased agonism has emerged as an attractive mechanism for A 1 R-mediated cardioprotection that is haemodynamically safe. Here we investigate the pre-clinical pharmacology, efficacy and side-effect profile of the A 1 R agonist neladenoson, shown to be safe but ineffective in phase IIb trials for the treatment of heart failure. We compare this agent with the well-characterised, pan-adenosine receptor (AR) agonist NECA, capadenoson, and the A 1 R biased agonist VCP746, previously shown to be safe and cardioprotective in pre-clinical models of heart failure. We show that like VCP746, neladenoson is biased away from Ca 2+ influx relative to NECA and the cAMP pathway at the A 1 R, a profile predictive of a lack of adenosine-like side effects. Additionally, neladenoson was also biased away from the MAPK pathway at the A 1 R. In contrast to VCP746, which displays more ‘adenosine-like’ signalling at the A 2B R, neladenoson was a highly selective A 1 R agonist, with biased, weak agonism at the A 2B R. Together these results show that unwanted haemodynamic effects of A 1 R agonists can be avoided by compounds biased away from Ca 2+ influx relative to cAMP, relative to NECA. The failure of neladenoson to reach primary endpoints in clinical trials suggests that A 1 R-mediated cAMP inhibition may be a poor indicator of effectiveness in chronic heart failure. This study provides additional information that can aid future screening and/or design of improved AR agonists that are safe and efficacious in treating heart failure in patients. Biased agonists that preference against calcium influx relative to the cyclic AMP pathway, when compared to a conventional agonist, confer clinical safety to A 1 adenosine receptor ligands.
β1- and β3-adrenoceptor mediated smooth muscle relaxation in hypothyroid rat ileum
Publisher: Elsevier BV
Date: 03-2001
DOI: 10.1016/S0014-2999(01)00795-6
Abstract: The effect of hypothyroidism on gastrointestinal beta(1)- and beta(3)-adrenoceptor function and expression was examined in rat ileal smooth muscle preparations. (-)-Isoprenaline and the selective beta(3) agonist disodium (R,R)-5-[2-[[2-3-chlorophenyl)-2-hydroxyethyl]-amino]propyl]-1,3-benzodioxole-2,2-dicarboxylate (CL 316234) relaxed both control and hypothyroid tissues in a dose-dependent manner. Responses to isoprenaline were reduced in tissues from hypothyroid rats, as was the shift produced with the beta(3)-adrenoceptor antagonist, 3-(2-ethylphenoxy)-1-[(1S)-1,2,3,4-tetrahydronaphth-1-ylamino]-(2S)-2-propanol oxalate (SR 59230A). No change was seen in responses to CL 316243. Experiments with a selective beta(1)-adrenoceptor antagonist produced results suggesting that isoprenaline did not act at this receptor. Messenger RNA levels for both beta(1)- and beta(2)-adrenoceptors were not affected by hypothyroidism. These results show that, unlike in adipose tissues, ileal beta(1)- and beta(3)-adrenoceptors are not directly regulated by thyroid hormone and that beta(3)-adrenoceptor coupling to the relaxation response is reduced in a rat model of hypothyroidism.
Structural requirements for the interaction of sheep insulin-like factor 3 with relaxin receptors in rat atria
Publisher: Elsevier BV
Date: 12-2002
DOI: 10.1016/S0014-2999(02)02662-6
Abstract: Relaxin is a peptide with various reproductive and nonreproductive functions. The site for the peptide-receptor interaction contains two arginines (Arg) and an isoleucine (Ile) or valine (Val) residue in the B-chain with a configuration of -Arg-X-X-X-Arg-X-X-Ile/Val-X-. The sheep insulin-like peptide 3 (INSL3), a structural homologue of relaxin, also contains the n, n+4 arginines in the B-chain but they are displaced towards the carboxyl terminus by four residues (-X-X-X-X-Arg-X-X-Val-Arg-). Human INSL3 increases the activity of human relaxin in mouse bioassays. Here, we investigated whether sheep synthetic INSL3 affects the relaxin activity in rat atria. INSL3 lacked relaxin-like agonist activity but blocked the activity of relaxin and competed for relaxin binding sites at high concentrations. We also synthesized analogues of INSL3, with amino acid substitutions in the arginine-binding region. Analogues A, D and E, which have the arginines in positions identical to relaxin, showed weak relaxin-like agonist activity. These results suggest that other sites in the relaxin molecule are involved in high-affinity peptide-receptor interaction for the production of the relaxin biological responses.
Multipathway In Vitro Pharmacological Characterization of Specialized Proresolving G Protein-Coupled Receptors
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 06-02-2022
DOI: 10.1124/MOLPHARM.121.000422
Abstract: Specialized proresolving mediators (SPMs) and their cognate G protein-coupled receptors are implicated in autoimmune disorders, including chronic inflammation, rheumatoid arthritis, systemic scleroderma, and lupus erythematosus. To date, six G protein-coupled receptors (GPCRs) have been paired with numerous endogenous and synthetic ligands. However, the function and downstream signaling of these receptors remains unclear. To address this knowledge gap, we systematically expressed each receptor in a human embryonic kindney 293 (HEK293)-Flp-In-CD8a-FLAG cell system. Each receptor was pharmacologically characterized with both synthetic and putative endogenous ligands across different signaling assays, covering both G protein-dependent (G
Evolution of β-blockers: from anti-anginal drugs to ligand-directed signalling
Publisher: Elsevier BV
Date: 04-2011
Agonist effects of zinterol at the mouse and human beta(3)-adrenoceptor.
Publisher: Springer Science and Business Media LLC
Date: 07-04-2006
DOI: 10.1007/S00210-006-0056-3
Abstract: The present study investigates the action of zinterol at beta(3)-adrenoceptors. We used mouse primary brown adipocytes and Chinese hamster ovary (CHO-K1) cells expressing the mouse or human beta(3)-adrenoceptor. Zinterol was a full agonist at increasing cyclic AMP levels in primary brown adipocytes (which express beta(1)- and beta(3)-adrenoceptors but not beta(2)-adrenoceptors), and this effect was almost totally abolished in adipocytes derived from beta(3)-adrenoceptor knock-out (KO) mice. Zinterol was also a full agonist at increasing another biological end-point, glucose uptake in brown adipocytes. This effect was reduced in adipocytes derived from beta(3)-adrenoceptor KO mice, with the remaining response sensitive to beta(1)-adrenoceptor antagonism. To determine whether the effect of zinterol on beta(3)-adrenoceptors in primary brown adipocytes can be replicated in a recombinant system, we used CHO-K1 cells expressing the mouse or human beta(3)-adrenoceptor. Zinterol was a full agonist at mouse and human receptors with respect to increasing cyclic AMP levels, with pEC(50) values similar to that of the selective beta(3)-adrenoceptor agonist (R, R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino]-propyl]1,3-benzodioxole-2,2-dicarboxylate (CL316243) at the mouse receptor. At the human receptor, zinterol was more potent at increasing cyclic AMP levels than CL316243. In cytosensor microphysiometer studies, zinterol was a full agonist for increases in extracellular acidification rates at the mouse and human beta(3)-adrenoceptor. Therefore, we have shown that zinterol is a potent, high-efficacy beta(3)-adrenoceptor agonist at the endogenous mouse beta(3)-adrenoceptor in primary brown adipocytes and at the cloned mouse and human beta(3)-adrenoceptor expressed in CHO-K1 cells. Zinterol is therefore one of few beta-adrenoceptor agonists with high potency and efficacy at the human beta(3)-adrenoceptor.
Comparison of signaling pathways activated by the relaxin family peptide receptors, RXFP1 and RXFP2, using reporter genes
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 25-10-2007
Abstract: The receptors for H2 relaxin and insulin-like peptide 3, relaxin family peptide receptor (RXFP) 1 and RXFP2, respectively, were recently identified, but their signaling pathways are not yet well characterized. Although previous work has suggested that cAMP is a major signaling pathway activated by these receptors, RXFP1 has also been shown to activate a number of other signaling proteins. To this end, we examined the effect of stimulation of RXFP1 and RXFP2 receptors [expressed in human embryonic kidney (HEK) 293T cells] with human relaxin family peptides on a number of transcription factor-response elements coupled to reporter genes. Hence, reporter gene activity measured by enzyme activity in the cell media is a measure of the activation of a particular signaling pathway. Eight reporter genes were tested at both receptors as a screen to identify other signaling pathways activated by RXFP1 and RXFP2. The cAMP-response element reporter was strongly activated by both receptors. This effect was enhanced by preincubation with pertussis toxin (PTX), suggesting that Gs and inhibitory Gi/Go proteins mediate this response. Only activation of RXFP1 inhibited nuclear factor kappaB transcription, and this was reversed by PTX and the phosphoinositide-3-kinase inhibitor wortmannin. In addition, the glucocorticoid-response element was activated by RXFP1 but not by RXFP2 and was not activated in the parent HEK293T cells. Thus, the use of reporter genes enabled differences in signaling between these two receptors to be revealed and also threw light on the wide range of effects attributed to relaxin.
Murine GPRC6A Mediates Cellular Responses to L-Amino Acids, but Not Osteocalcin Variants
Publisher: Public Library of Science (PLoS)
Date: 19-01-2016
Autoradiographic analysis of the distribution of β‐adrenoceptors in the dog splenic vasculature
Publisher: Wiley
Date: 03-1986
DOI: 10.1111/J.1476-5381.1986.TB10203.X
Abstract: The technique of in vitro labelling and autoradiography has been used to localize beta-adrenoceptors in sections of the splenic vascular bundle of the dog. Binding of (-)-[125I]-cyanopindolol (Cyp) to sections of splenic vascular bundle equilibrated within 150 min and slowly dissociated after addition of (-)-propranolol. The process was saturable with a dissociation constant (KD) of 40.3 +/- 4.4 pM and Bmax of 18.9 +/- 1.7 fM (in 6 sections). Binding to sections was stereoselective, the (-)-isomer of propranolol being 90 times more effective than the (+)-isomer in competing for (-)-[125I]-Cyp binding. Delineation of beta-adrenoceptor subtypes using the selective antagonists betaxolol (beta 1) and ICI 118,551 (beta 2) indicated that the receptors present were almost exclusively of the beta 2-subtype. Autoradiographic studies under the conditions evaluated in the biochemical experiments showed that beta-adrenoceptors are unevenly distributed in the dog splenic vein, artery and associated nerve bundles. High concentrations of receptors are associated with the splenic nerves and lower but still significant concentrations in the vasculature. Higher resolution studies with nuclear emulsion coated coverslips revealed concentrations of beta-adrenoceptors over cells adjacent to the lumen in veins. In arteries most beta-adrenoceptors were found associated with the medial layer with fewer receptors towards the intima or adventitia. Serial sections of either artery or vein incubated with (-)-[125I]-Cyp in the presence of (-)-propranolol showed low levels of non-localized binding.
Adrenoceptors—New roles for old players
Publisher: Wiley
Date: 25-06-2019
DOI: 10.1111/BPH.14701
Role of beta-adrenoceptors in memory consolidation: beta3-adrenoceptors act on glucose uptake and beta2-adrenoceptors on glycogenolysis.
Publisher: Springer Science and Business Media LLC
Date: 28-11-2008
Abstract: Noradrenaline, acting via beta(2)- and beta(3)-adrenoceptors (AR), enhances memory formation in single trial-discriminated avoidance learning in day-old chicks by mechanisms involving changes in metabolism of glucose and/or glycogen. Earlier studies of memory consolidation in chicks implicated beta(3)- rather than beta(2)-ARs in enhancement of memory consolidation by glucose, but did not elucidate whether stimulation of glucose uptake or of glycolysis was responsible. This study examines the role of glucose transport in memory formation using central injection of the nonselective facilitative glucose transporter (GLUT) inhibitor cytochalasin B, the endothelial/astrocytic GLUT-1 inhibitor phloretin and the Na(+)/energy-dependent endothelial glucose transporter (SGLT) inhibitor phlorizin. Cytochalasin B inhibited memory when injected into the mesopallium (avian cortex) either close to or between 25 and 45 min after training, whereas phloretin and phlorizin only inhibited memory at 30 min. This suggested that astrocytic/endothelial (GLUT-1) transport is critical at the time of consolidation, whereas a different transporter, probably the neuronal glucose transporter (GLUT-3), is important at the time of training. Inhibition of glucose transport by cytochalasin B, phloretin, or phlorizin also interfered with beta(3)-AR-mediated memory enhancement 20 min posttraining, whereas inhibition of glycogenolysis interfered with beta(2)-AR agonist enhancement of memory. We conclude that in astrocytes (1) activities of both GLUT-1 and SGLT are essential for memory consolidation 30 min posttraining (2) neuronal GLUT-3 is essential at the time of training and (3) beta(2)- and beta(3)-ARs consolidate memory by different mechanisms beta(3)-ARs stimulate central glucose transport, whereas beta(2)-ARs stimulate central glycogenolysis.
Light microscopic autoradiography of the distribution of [3H]rauwolscine binding to α2-adrenoceptors in rat kidney
Publisher: Elsevier BV
Date: 10-1985
DOI: 10.1016/0014-2999(85)90162-1
Abstract: The localization of [3H]rauwolscine binding to microscope slide mounted sections of rat kidney has been examined using the technique of in vitro labelling and autoradiography. Binding to sections equilibrated within 60 min and was reversible following the addition of 10 microM phentolamine. Saturation studies revealed a single population of high affinity (KD 4.27 nM) non-interacting sites (nH 0.97) with a density of 11.1 fmol/section. Stereoselectivity was observed with respect to the isomers of noradrenaline and the relative affinity of a series of alpha-adrenoceptor antagonists suggested binding to alpha 2-adrenoceptors. Autoradiographic studies using 3H-Ultrofilm showed that the binding is largely confined to the renal cortex. More detailed studies using emulsion coated coverslips indicates that the major concentration of binding sites is over the proximal tubules. This study provides evidence that alpha 2-adrenoceptors, known to be coupled in an inhibitory fashion to renal adenylate cyclase, are highly localized to particular structures in the kidney.
Addition of a Carboxy‐Terminal Green Fluorescent Protein Does Not Alter the Binding and Signaling Properties of Relaxin Family Peptide Receptor 3
Publisher: Wiley
Date: 04-2009
DOI: 10.1111/J.1749-6632.2008.03818.X
Abstract: The relaxin family peptide receptor 3 (RXFP3) is the cognate receptor for the neuropeptide relaxin-3. RXFP3 was tagged at the carboxy-terminus with a variant of the green fluorescent protein (GFP(2)) for use in receptor localization studies. RXFP3-GFP(2) was examined to ensure it retained binding and signaling properties similar to untagged RXFP3. Competition for [(125)I]INSL5/H3 relaxin chimera binding to RXFP3 and RXFP3-GFP(2) indicated that the carboxy-terminal tag did not affect receptor binding or receptor internalization. RXFP3-GFP(2) activated ERK1/2 with a similar potency to RXFP3 when transiently expressed in CHO-K1 or HEK293T cells, suggesting that the GFP(2) tag did not affect receptor function. This study demonstrated that addition of a carboxy-terminal fusion protein to RXFP3 did not alter the binding or signaling properties of RXFP3, making RXFP3-GFP(2) a useful tool for future receptor localization and trafficking studies.
BRL37344 stimulates GLUT4 translocation and glucose uptake in skeletal muscle via β2-adrenoceptors without causing classical receptor desensitization.
Publisher: American Physiological Society
Date: 05-2019
DOI: 10.1152/AJPREGU.00285.2018
Abstract: The type 2 diabetes epidemic makes it important to find insulin-independent ways to improve glucose homeostasis. This study examines the mechanisms activated by a dual β 2 -/β 3 -adrenoceptor agonist, BRL37344, to increase glucose uptake in skeletal muscle and its effects on glucose homeostasis in vivo. We measured the effect of BRL37344 on glucose uptake, glucose transporter 4 (GLUT4) translocation, cAMP levels, β 2 -adrenoceptor desensitization, β-arrestin recruitment, Akt, AMPK, and mammalian target of rapamycin (mTOR) phosphorylation using L6 skeletal muscle cells as a model. We further tested the ability of BRL37344 to modulate skeletal muscle glucose metabolism in animal models (glucose tolerance tests and in vivo and ex vivo skeletal muscle glucose uptake). In L6 cells, BRL37344 increased GLUT4 translocation and glucose uptake only by activation of β 2 -adrenoceptors, with a similar potency and efficacy to that of the nonselective β-adrenoceptor agonist isoprenaline, despite being a partial agonist with respect to cAMP generation. GLUT4 translocation occurred independently of Akt and AMPK phosphorylation but was dependent on mTORC2. Furthermore, in contrast to isoprenaline, BRL37344 did not promote agonist-mediated desensitization and failed to recruit β-arrestin1/2 to the β 2 -adrenoceptor. In conclusion, BRL37344 improved glucose tolerance and increased glucose uptake into skeletal muscle in vivo and ex vivo through a β 2 -adrenoceptor-mediated mechanism independently of Akt. BRL37344 was a partial agonist with respect to cAMP, but a full agonist for glucose uptake, and importantly did not cause classical receptor desensitization or internalization of the receptor.
PHARMACOLOGICAL INVESTIGATION OF α-ADRENORECEPTORS IN GUINEA-PIG SPLENIC CAPSULE
Publisher: Wiley
Date: 09-1981
DOI: 10.1111/J.1474-8673.1981.TB00461.X
Abstract: 1. A study has been made of alpha-adrenoreceptors in the smooth muscle of the guinea-pig splenic capsule. 2. In this preparation, noradrenaline (NA), adrenaline (Adr) and alpha-methyl-NA were full agonists, while phenylephrine, dopamine and the catechol-imidazolidine (3,4-dihydroxyphenylamino)-2-imidazolidine, (DPI) were partial agonists. 3. The imidazolidines clonidine and oxymetazoline showed no agonist activity, but both inhibited the agonist activity of NA. pA2 values calculated from Arunlakshana and Schild plots were 6.88 and 6.95 for clonidine and oxymetazoline respectively. Slopes of the Schild plots were close to unity, indicating competitive antagonism. 4. The alpha-adrenoreceptor antagonists phentolamine, prazosin and yohimbine also inhibited the agonist activity of NA with man pA2 values of 8.32, 9.22 and 6.90 respectively. Slopes of Schild plots were significantly less than 1, suggesting that the inhibition was not truly competitive in nature. 5. The irreversible alpha-adrenoreceptor antagonist phenoxybenzamine at low concentrations (10(-9)M) shifted the log concentration-response curve to NA to the right and greatly reduced the maximum response. 6. It is suggested that the adrenoreceptors in the guinea-pig splenic capsule are probably of the alpha 1-type, and that this tissue possesses relatively few spare receptors.
Cardiac effects of relaxin
Publisher: Elsevier BV
Date: 06-1993
The pharmacology of labetalol, an α- and β-adrenoceptor blocking agent
Publisher: Elsevier BV
Date: 1978
DOI: 10.1016/0306-3623(78)90024-1
Abstract: Intact amyloplasts from potato (Solanum tuberosum L.) were used to study starch biosynthesis and phosphorylation. Assessed by the degree of intactness and by the level of cytosolic and vacuolar contamination, the best preparations were selected by searching for amyloplasts containing small starch grains. The isolated, small amyloplasts were 80% intact and were free from cytosolic and vacuolar contamination. Biosynthetic studies of the amyloplasts showed that [1-14C]glucose-6-phosphate (Glc-6-P) was an efficient precursor for starch synthesis in a manner highly dependent on amyloplast integrity. Starch biosynthesis from [1-14C]Glc-1-P in small, intact amyloplasts was 5-fold lower and largely independent of amyloplast intactness. When [33P]Glc-6-P was administered to the amyloplasts, radiophosphorylated starch was produced. Isoamylase treatment of the starch followed by high-performance anion-exchange chromatography with pulsed erometric detection revealed the separated phosphorylated alpha-glucans. Acid hydrolysis of the phosphorylated alpha-glucans and high-performance anion-exchange chromatography analyses showed that the incorporated phosphate was preferentially positioned at C-6 of the Glc moiety. The incorporation of radiolabel from Glc-1-P into starch in preparations of amyloplasts containing large grains was independent of intactness and most likely catalyzed by starch phosphorylase bound to naked starch grains.
Autoradiographic Localization and Quantitation of β1- and β2-Adrenoceptors in the Human Atrioventricular Conducting System: A Comparison of Patients with Idiopathic Dilated Cardiomyopathy and Ischemic
Publisher: Elsevier BV
Date: 03-1994
Abstract: The density and distribution of beta 1- and beta 2-adrenoceptors in the atrioventricular conducting system and interatrial and interventricular septa from human hearts with idiopathic dilated cardiomyopathy and ischemic heart disease was determined by quantitative autoradiography using (-)[125I]cyanopindolol and the selective beta 1-adrenoceptor antagonist CGP 20712A and the selective beta 2-adrenoceptor antagonist ICI 118,551. Both beta 1- and beta 2-adrenoceptors were present in the atrioventricular node, bundle of His, interatrial and interventricular septa. No differences in the density or proportions of beta 1- and beta 2-adrenoceptors in the atrioventricular node, bundle of His, interatrial septum and interventricular septum were observed between hearts with idiopathic dilated cardiomyopathy or ischemic heart disease (P > 0.05) so further analysis did not distinguish between the two aetiologies. The density of beta 1-adrenoceptors was lower in the bundle of His (5.0 +/- 1.7 fmol/mg protein) than in the atrioventricular node (22.2 +/- 5.7 fmol/mg protein, P < 0.05), the interatrial septum (29.6 +/- 4.5 fmol/mg protein, P < 0.001) and interventricular septum (24.9 +/- 5.2 fmol/mg protein, P < 0.005, n = 8 for all values). The atrioventricular node, interatrial and interventricular septa had similar densities of beta 1-adrenoceptors (P = 0.60, ANOVA). The distribution of beta 2-adrenoceptors in the atrioventricular node (21.5 +/- 4.1 fmol/mg protein), bundle of His (12.9 +/- 2.6 fmol/mg protein) and atrial (16.7 +/- 2.3 fmol/mg protein) and septal myocardium (13.8 +/- 2.5 fmol/mg protein, n = 8 for all values) was uniform (P = 0.18, ANOVA). The percentage of beta 1- and beta 2-adrenoceptors in the atrioventricular node, bundle of His, interatrial and interventricular septa was uneven (P < 0.001, ANOVA). There was a higher proportion of beta 2-adrenoceptors in the bundle of His (72 +/- 6%) than in the atrioventricular node (51 +/- 3%, P < 0.01), interatrial septum (36 +/- 1%, P < 0.001) and interventricular septum (36 +/- 1%, P < 0.001).
Regulation of ß-adrenoceptors in the guinea-pig sinoatrial node
Publisher: Springer Science and Business Media LLC
Date: 05-1994
DOI: 10.1007/BF00169134
Autoradiographic localization and characterization of substance P binding in dog kidney
Publisher: Elsevier BV
Date: 10-1987
DOI: 10.1016/0014-2999(87)90078-1
Abstract: The autoradiographic localization of [125I]Bolton-Hunter substance P (BHSP) was examined in slide-mounted sections of dog kidney and dog renal artery and vein. Biochemical characterization of the binding in sections of dog kidney, demonstrated that BHSP binds to a population of non-interacting sites with high affinity (KD = 0.11 +/- 0.02 nM, Bmax = 0.29 +/- 0.05 fmol/section). The binding was displaced by tachykinins in the order SP greater than NKA much greater than NKB, indicative of binding to NK-1 receptors. BHSP binding to dog kidney was localized over glomeruli and endothelium of intrarenal arteries. There was binding associated with the endothelium and adventitia of the renal artery but not the vein. Binding of BHSP to arcuate arteries and to the renal artery was dependent on the presence of an intact endothelium. No evidence was obtained for receptors associated with any renal tubules. These results suggest that in the dog, vasodilation, diuresis and natriuresis in response to SP may result from an action primarily on the vascular elements of the kidney.
β‐ADRENOCEPTORS IN CIRCULAR AND LONGITUDINAL MYOMETRIAL MEMBRANES AND IN LUNG MEMBRANES FROM DIOESTROUS AND POST‐PARTUM GUINEA‐PIGS
Publisher: Wiley
Date: 09-1988
DOI: 10.1111/J.1440-1681.1988.TB01128.X
Abstract: 1. We have examined the binding of (-)[125]-cyanopindolol ((-)[125I]-CYP) to membranes prepared from uterus and lung of dioestrous and post-partum (1-6 days) guinea-pigs. 2. The densities of beta-adrenoceptor binding sites in circular and longitudinal myometrium from dioestrous animals were similar, and approximately one-eight of those in the lung. Ascorbate and ethylenediaminetetraacetic acid in the incubation medium did not affect binding. 3. The numbers and affinities of beta-adrenoceptor binding sites in both myometrial layers and in lung parenchyma from post-partum animals were similar to those in corresponding tissues from dioestrous animals. 4. The distribution of beta-adrenoceptor binding sites in the post-partum uterus was examined using receptor autoradiography. Binding to circular and longitudinal muscle layers and to the endometrium was inhibited by (-)-propranolol (1 mumol/l), by the beta 2-adrenoceptor selective antagonist ICI 118,551 (70 nmol/l), but not by the beta 1-adrenoceptor selective antagonist CGP 20712A (100 nmol/l), indicating that the beta-adrenoceptor present was of the beta 2-subtype. 5. The ability of isoprenaline to compete for (--)[125]-CYP binding sites in uterine membranes from post-partum animals was approximately twice that in corresponding preparations from dioestrous animals. 6. Changes in the numbers or affinity of beta 2-adrenoceptors cannot account for the marked and selective enhancement of the actions of sympathomimetic amines at beta-adrenoceptors previously observed in longitudinal myometrium taken from post-partum guinea-pigs. It is suggested that enhancement of later steps in the chain of events between beta-adrenoceptor occupancy and uterine relaxation, and/or a decrease in the contribution of alpha-adrenoceptors to the net effect of the amine might provide alternative explanations.
Relaxin antagonizes hypertrophy and apoptosis in neonatal rat cardiomyocytes
Publisher: The Endocrine Society
Date: 04-2007
DOI: 10.1210/EN.2006-1324
Abstract: The pregnancy hormone relaxin has recently been shown to be cardio-protective. Despite its well-established antifibrotic actions in the heart, the effects of relaxin on cardiomyocytes (CM) remain to be determined. We investigated effects of isoform 2 of the human relaxin (H2-relaxin) on CM hypertrophy and apoptosis. In cultured neonatal rat CM, phenylephrine (50 μm) and cardiac fibroblast-conditioned medium were used respectively to induce CM hypertrophy. The degree of hypertrophy was indicated by increased cell size, protein synthesis and gene expression of atrial natriuretic peptide. Although H2-relaxin (16.7 nm) alone failed to suppress hypertrophy induced by phenylephrine, it repressed the cardiac fibroblast-conditioned medium-induced increase in protein synthesis by 24% (P & 0.05) and reversed the increase in cell size (P & 0.001) and atrial natriuretic peptide expression (P& .01). We further studied the effect of H2-relaxin on CM apoptosis induced by H2O2 (200 μm). Studies of DNA laddering and nuclear staining demonstrated that H2-relaxin treatment reduced H2O2-induced DNA fragmentation. Real-time PCR and Western blot analysis revealed a significant increase in the Bcl2/Bax ratio in H2-relaxin-treated CM. Further analysis showed that activation of Akt (1.8-fold, P& 0.001) and ERK (2.0-fold, P& .01) were involved in the antiapoptotic action of H2-relaxin in CM, and that Gi/o coupling of relaxin receptors was associated with the H2-relaxin-induced Akt activation in CM. In conclusion, these results extend our current knowledge of the cardiac actions of relaxin by demonstrating that H2-relaxin indirectly inhibits CM hypertrophy and directly protects CM from apoptosis.
Solid‐phase synthesis of ovine Leydig cell insulin‐like peptide – a putative ovine relaxin?
Publisher: Wiley
Date: 05-1999
DOI: 10.1034/J.1399-3011.1999.00060.X
Abstract: The primary structure of ovine Leydig cell insulin-like peptide (Ley I-L) was recently deduced from the corresponding cDNA sequence. It consists of two peptide chains and three disulphide bonds in an arrangement similar to both relaxin and insulin. As in relaxin B-chain, an Arg-X-X-X-Arg sequence exists within the Ley I-L B-chain although it is located four residues towards the C-terminus from the corresponding position within relaxin. This sequence of amino acids is known to be essential for relaxin biological activity and its presence in Ley I-L suggested that the peptide might possess a relaxin-like function. Ovine Ley I-L was assembled by Fmoc-solid-phase synthesis of the separate chains followed by their combination in solution at high pH. The purity and identity of the chain-combined peptide was confirmed by chemical characterization including mass spectrometry. At physiological concentrations, the peptide was shown not to possess relaxin-like activity in the rat isolated atrial chronotropic and inotropic assay. This strongly suggests that Ley I-L is not a relaxin in the sheep. In order to explore further a possible structural relationship between Ley I-L and relaxin, we prepared a synthetic analogue of ovine Ley I-L containing a single replacement of B-chain residue 12, His, with Arg. This was found to possess significant relaxin-like chronotropic and inotropic activity demonstrating that the tertiary structure of Ley I-L is similar to that of relaxin and highlighting the key requirement for the five-residue sequence, Arg-X-X-X-Arg, to be present in position B12-16 for characteristic relaxin activity.
Allosteric Ligands of the Glucagon-Like Peptide 1 Receptor (GLP-1R) Differentially Modulate Endogenous and Exogenous Peptide Responses in a Pathway-Selective Manner: Implications for Drug Screening
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 14-06-2010
H2 Relaxin Is a Biased Ligand Relative to H3 Relaxin at the Relaxin Family Peptide Receptor 3 (RXFP3)
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 16-02-2010
Abstract: Relaxin family peptide 3 receptors (RXFP3) are activated by H3-relaxin to inhibit forskolin-stimulated cAMP accumulation and stimulate extracellular signal-regulated kinase (ERK) 1/2 phosphorylation. In this study, we sought to identify novel signaling pathways coupled to RXFP3 and to investigate whether other members of the relaxin peptide family activated these pathways. Two patterns of signaling were observed in RXFP3-expressing Chinese hamster ovary (CHO)-K1 and human embryonic kidney (HEK)-293 cells (CHO-RXFP3 and HEK-RXFP3) and murine septal neuron SN56 cell lines: 1) strong inhibition of forskolin-stimulated cAMP accumulation, ERK1/2 activation and nuclear factor (NF)-kappaB reporter gene activation in cells stimulated with H3 relaxin, with weaker activity observed for H2 relaxin, porcine relaxin, or insulin-like peptide (INSL) 3 and 2) strong stimulation of activator protein (AP)-1 reporter genes by H2 relaxin, with weaker activation observed with H3 or porcine relaxin. Two distinct ligand binding sites were identified on RXFP3-expressing cells using two different radioligands. (125)I-INSL5 A-chain/relaxin-3 B-chain chimera bound with high affinity to the RXFP3-expressing cells with competition by H3 relaxin or a H3 relaxin B-chain dimeric peptide, consistent with previous reports. Binding studies with (125)I-H2 relaxin revealed a distinct binding site with potent competition observed with H2 relaxin, H3 relaxin, or INSL3 and weaker competition with porcine relaxin. Thus H3 relaxin potently activates all signaling pathways coupled to RXFP3, whereas H2 relaxin is an AP-1-biased ligand relative to H3 relaxin.
Antifibrotic Actions of Serelaxin – New Roles for an Old Player
Publisher: Elsevier BV
Date: 06-2016
DOI: 10.1016/J.TIPS.2016.02.007
Abstract: Fibrosis represents a failed wound healing response to tissue injury. It is characterized by the accumulation of excess connective tissue and is a significant cause of organ failure, morbidity, and mortality. Fibrotic disorders accompany a wide spectrum of conditions including both systemic and organ-specific diseases, for which there is currently no effective cure. Serelaxin, the recombinant form of the major stored and circulating form of human relaxin, has emerged as a pleiotropic drug with rapidly occurring antifibrotic actions. This review discusses the effectiveness of serelaxin as an antifibrotic, and how it augments the actions of several other therapeutics leading to its potential use not only as a monotherapy but also as an adjunct therapy with other antifibrotic agents.
Engineering of a Novel Simplified Human Insulin-Like Peptide 5 Agonist.
Publisher: American Chemical Society (ACS)
Date: 12-02-2016
DOI: 10.1021/ACS.JMEDCHEM.5B01786
Abstract: Insulin-like peptide 5 (INSL5) has recently been discovered as only the second orexigenic gut hormone after ghrelin. As we have previously reported, INSL5 is extremely difficult to assemble and oxidize into its two-chain three-disulfide structure. The focus of this study was to generate structure-activity relationships (SARs) of INSL5 and use it to develop a potent and simpler INSL5 mimetic with RXFP4 agonist activity. A series of human and mouse INSL5 (hINSL5/mINSL5) analogues were designed and chemically synthesized, resulting in a chimeric INSL5 analogue exhibiting more than 10-fold higher potency (0.35 nM) at human RXFP4 compared with native hINSL5 (4.57 nM). The SAR study also identified a key residue (K(A15)) in the A-chain of mINSL5 that contributes to improved RXFP4 affinity and potency of mINSL5 compared with hINSL5. This knowledge ultimately led us to engineer a minimized hINSL5 mimetic agonist that retains native hINSL5-like RXFP4 affinity and potency at human RXFP4. This minimized analogue was synthesized in 17.5-fold higher yield and in less time compared with hINSL5.
Alternative splicing generates two isoforms of the β3‐adrenoceptor which are differentially expressed in mouse tissues
Publisher: Wiley
Date: 07-1999
[3H]-GUANFACINE: A RADIOLIGAND THAT SELECTIVELY LABELS HIGH AFFINITY α2-ADRENOCEPTOR SITES IN HOMOGENATES OF RAT BRAIN
Publisher: Wiley
Date: 02-1982
DOI: 10.1111/J.1476-5381.1982.TB08801.X
Abstract: [3H]-guanfacine (N-amidino-2-(2,6-dichloro 3[3H] phenyl) acetamide hydrochloride 24.2 Ci/mmol) has been used as a radioligand in homogenates of rat cerebral cortex. Specific binding of [3H]-guanfacine was linear with respect to tissue concentration (2.5-15 mg/ml), saturable and not markedly affected in the pH range 6.5-8.0. Analysis of the saturation of [3H]-guanfacine binding using an iterative least squares fitting procedure gave best fits to a single site model. [3H]-guanfacine binding was of high affinity (Kd 1.77 +/- 0.24 nM n = 8) to a population of non interacting sites (nH 0.99 +/- 0.02 n = 8) with a density of 118.2 +/- 8.4 fmol/mg protein (n = 8). Highest levels of binding were achieved in cerebral cortex followed by thalamus greater than hypothalamus greater than medulla ons greater than spinal cord greater than striatum greater than cerebellum. Binding was stereoselective with regard to the (-)-isomer of noradrenaline and the order of potency for displacement of [3H]-guanfacine by agonists was naphazoline greater than clonidine greater than (-)-adrenaline greater than (-)-alpha methylnoradrenaline greater than (-)-noradrenaline greater than (+/-)-alpha-methylnoradrenaline greater than (+)-noradrenaline greater than methoxamine greater than (+)-adrenaline greater than phenylephrine and by antagonists was phentolamine greater than dihydroergocryptine greater than piperoxane greater than yohimbine greater than prazosin greater than labetalol greater than indoramin suggested binding to alpha 2-adrenoceptors. The monovalent cations Na+ and K+ and also guanosine 5'-triphosphate (GTP) produced concentration-dependent inhibition whereas the alent cations Ca2+, Mg2+, and Mn2+ first enhanced, then inhibited [3H]-guanfacine binding. Na+ (150 mM) or GTP (100 microM) produced marked reductions and Mn2+ (5 mM) marked increases in the number of receptor sites labelled by [3H]-guanfacine. 9 It is concluded that [3H]-guanfacine preferentially labels a high affinity state of the alpha 2- adrenoceptor in homogenates of rat cerebral cortex.
Age Related Changes of Catecholamines and Their Metabolites in Central Nervous System Regions of Spontaneously Hypertensive (SHR) and Normotensive Wistar-Kyoto (Wky) Rats:
Publisher: Informa UK Limited
Date: 1984
DOI: 10.3109/10641968409052207
Abstract: Adrenaline (A), dopamine (DA), noradrenaline (NA) the NA metabolite 3,4-dihydroxyphenylethylene-glycol (DHPG) and the DA metabolite 3,4 dihydroxyphenylacetic acid (DOPAC) were assayed in brain regions of male and female WKY and SHR at 6, 14, 28 and 36-40 weeks. Age related differences in catecholamine levels between the two strains were only seen with NA measurements. DOPAC levels were elevated in the striatum of SHR compared to WKY rats at all ages studied which might reflect the known hyperactivity of SHR strain. In the SHR NA but not DHPG levels in several regions, DA and DOPAC levels in midbrain and DA levels in lower brainstem were elevated at 6 weeks of age. These changes may represent a generalized alteration in central catecholamine metabolism in SHR during the early development of hypertension or merely reflect strain differences. It is emphasised that further genetic studies of F2 backcross rats are required to establish an aetiological association between these differences in catechol levels and differences in blood pressure between SHR and WKY rats.
Rosiglitazone and a β3-Adrenoceptor Agonist Are Both Required for Functional Browning of White Adipocytes in Culture.
Publisher: Frontiers Media SA
Date: 30-05-2018
An uptake mechanism for L-noradrenaline in the cat spleen, associated with the nerves but distinct from uptake1
Publisher: Wiley
Date: 04-1974
DOI: 10.1113/JPHYSIOL.1974.SP010518
Abstract: 1. The characteristics of the uptake of [(3)H]L-noradrenaline from 1 mug pulses injected close arterially to the isolated blood perfused cat spleen are described.2. The spleen took up 355.0+/-16.0 ng from a first pulse and 321.1+/-43.6 ng from a second.3. Uptake from a second pulse was 254.0+/-30.3 ng in the presence of the Uptake(1) inhibitor desmethylimipramine (DMI) (3.3 x 10(-5)M) and the Uptake(2) inhibitor 17-beta-oestradiol (17beta0) (1.8 x 10(-4)M).4. Uptake from small 10 ng pulses was also insensitive to DMI and 17beta0.5. Uptake from pulses was abolished by surgical denervation of the spleen, or pre-treatment with phenoxybenzamine (PBA) (8.8 x 10(-5)M).6. The pulse uptake process was impaired by omission of red cells from the perfusate.7. Stimulation of the splenic nerves at 3Hz halved the pulse uptake.8. Uptake from infusion in the presence of DMI and 17beta0 occurred only during the first few minutes of the infusion.9. It is concluded that an uptake process for L-noradrenaline distinct from Uptakes(1) and (2) is present in the spleen and this might be important physiologically.
Excitatory amino acid projections to the nucleus of the solitary tract in the rat: a retrograde transport study utilizing d-[3H]aspartate and [3H]GABA
Publisher: Elsevier BV
Date: 12-1994
β‐Adrenoceptor regulation in rat heart, lung and skin after chronic treatment with (‐)‐tertatolol or (‐)‐propranolol
Publisher: Wiley
Date: 12-1995
DOI: 10.1111/J.1474-8673.1995.TB00407.X
Abstract: 1. The effect of long-term treatment with the beta-adrenoceptor antagonists (--)-tertatolol and (--)-propranolol was studied. Sprague-Dawley rats were treated with either (--)-tertatolol (50 micrograms kg-1 hr-1), (--)-propranolol (250 micrograms kg-1 hr-1) or vehicle (1 mM HCl) for 14 days with osmotic minipumps implanted subcutaneously. 2. The mean daily systolic blood pressure and heart rate of rats treated with either (--)-tertatolol (108 +/- 1 mmHg/330 +/- 3 bpm) or (--)-propranolol (103 +/- 1 mmHg/330 +/- 2 bpm) were lower than in the control (126 +/- 1 mmHg/405 +/- 3 bpm, P 0.05). Nevertheless, the receptor population in the homogenates of (--)-tertatolol treated lung were halved (194 +/- 28 fmol mg protein-1 compared with a control value of 388 +/- 54 fmol mg protein-1, P < 0.01, n = 6). 4. In the presence of CGP 20712A, the left atrial inotropic and right atrial chronotropic responsiveness to (--)-isoprenaline were hypersensitive in both (--)-tertatolol and (--)-propranolol-treated groups (P < 0.005, ANCOVA). 5. (--)-Propranolol treated left ventricular free wall had lower basal [3H]-forskolin binding to adenylate cyclase (14.45 +/- 1.20 fmol mg protein-1 compared with a control value of 18.91 +/- 0.78 fmol mg protein-1, P = 0.01, n = 6). (--)-Tertatolol treatment had no effect on the basal binding. In the presence of the G-protein activators NaF and Gpp(NH)p, the enhancement of [3H]-forskolin binding did not differ between control and the drug treated groups. 6. Chronic (--)-tertatolol or (--)-propranolol treatment therefore did not produce an increase in receptors in heart, lung or skin but the beta-adrenoceptor-mediated responses were enhanced. In addition, [3H]-forskolin binding did not increase suggesting that the hypersensitivity was not due to changes in the number of receptors or adenylate cyclase. Hypersensitivity following beta-adrenoreceptor antagonist administration may therefore involve enhanced coupling of receptors to G-proteins.
Comparative genotypic and phenotypic analysis of human peripheral blood monocytes and surrogate monocyte-like cell lines commonly used in metabolic disease research
Publisher: Public Library of Science (PLoS)
Date: 10-05-2018
Molecular pharmacology of G protein‐coupled receptors
Publisher: Wiley
Date: 28-09-2016
DOI: 10.1111/BPH.13610
Autoradiographic localization and function of β‐adrenoceptors on the human internal mammary artery and saphenous vein
Publisher: Wiley
Date: 09-1988
DOI: 10.1111/J.1476-5381.1988.TB16568.X
Abstract: 1. Receptor autoradiography with (-)-[125I]-cyanopindolol (CYP) was used to study the distribution of beta 1- and beta 2-adrenoceptor subtypes in the human internal mammary artery and saphenous vein. 2. Images from X-ray film and nuclear emulsion coated coverslips, exposed to [125I]-CYP labelled sections, showed a high density of beta 2-adrenoceptors localized to the endothelium of the internal mammary artery and fewer beta 2-adrenoceptors on the smooth muscle. 3. The function of beta-adrenoceptors in ring preparations of the internal mammary artery was investigated in organ bath studies. (-)-Isoprenaline produced concentration-dependent relaxation of phenylephrine contracted rings. The potency and maximal effects of (-)-isoprenaline were not influenced by the presence of the endothelium. 4. Images of [125I]-CYP binding to the saphenous vein, from X-ray film and nuclear emulsion coated coverslips, showed localization of beta 2-adrenoceptors to the outer smooth muscle and not to the endothelium. 5. Relaxation of mammary artery and saphenous vein to (-)-isoprenaline is mediated via beta 2-adrenoceptors located on the smooth muscle. Endothelial beta 2-adrenoceptors, although present on the internal mammary artery, mediate other functions.
Reduced glutamate binding in rat dorsal vagal complex after nodose ganglionectomy
Publisher: Elsevier BV
Date: 12-1988
DOI: 10.1016/0361-9230(88)90026-3
Abstract: Quantitative receptor autoradiography with L-[3H]glutamate was employed to examine the distribution and properties of glutamate binding sites in the rat brain 14 days after excision of the right nodose ganglion. Slide-mounted coronal sections of the brain showed reduced L-[3H]glutamate binding in the nucleus tractus solitarius/dorsal motor nucleus of the vagus in the ipsilateral relative to the sham-operated side. Densitometric and saturation analyses of binding data indicated a significant reduction in the density of glutamate binding sites (57% decrease relative to sham), while there was a significant increase in receptor affinity (40% greater than sham). Binding was unaltered in the inferior olivary complex. Glutamate receptors are likely to exist on synaptic nerve terminals of vagal afferent fibres within the nucleus tractus solitarius and on vagal preganglionic neurones within the dorsal motor nucleus of the vagus and/or their dendritic processes within the nucleus tractus solitarius. Additionally, our receptor autoradiographic studies provide evidence for L-glutamate being a transmitter of vagal afferent neurones.
Structure–function analyses of a pertussis-like toxin from pathogenic Escherichia coli reveal a distinct mechanism of inhibition of trimeric G-proteins
Publisher: Elsevier BV
Date: 09-2017
Effects of glucose and 2-deoxyglucose on memory formation in the chick: interaction with β3-adrenoceptor agonists
Publisher: Elsevier BV
Date: 09-2002
DOI: 10.1016/S0306-4522(02)00229-4
Abstract: Consolidation of a weakly reinforced memory that would otherwise fade after 30 min can be achieved by central or peripheral injection of the selective beta(3)-adrenoceptor agonist CL316243 as well as the beta(2)-adrenoceptor agonist zinterol and the alpha(1)-adrenoceptor antagonist prazosin in the day-old chick. The effect of the beta(3)-adrenoceptor agonist is mimicked by peripheral or central injection of glucose that is effective in enhancing memory from 25 min before to 25 min after training. Glucose uptake into various cell types has been described following activation of beta(3)-adrenoceptors and in this paper we demonstrate that activation of beta(3)-adrenoceptors by CL316243 facilitates the effect of a dose of glucose that does not normally enhance memory, whereas a beta(2)-adrenoceptor agonist and an alpha(1)-adrenoceptor antagonist have no effect. Administration of the glucose uptake inhibitor 2-deoxyglucose prevented the consolidation of strongly reinforced training. The beta(3)-adrenoceptor agonist facilitated the effect of a non-amnestic dose of 2-deoxyglucose to inhibit memory. There are two time periods relative to the learning trial where memory is vulnerable to interference by centrally administered 2-deoxyglucose: one related to short-term memory and one at the time of consolidation into long-term memory. Peripheral injection of 2-deoxyglucose is only effective at the time of consolidation. The action of the beta(3)-adrenoceptor agonist to facilitate the action of 2-deoxyglucose only occurs at the time of consolidation. We suggest that a noradrenergic agonist acting at beta(3)-adrenoceptors enhances memory formation by facilitation of glucose uptake at the time of memory consolidation. This may represent a novel mechanism that would be beneficial for developing compounds for the facilitation of memory in diseases with cognitive deficits.
Relaxin deficiency in mice is associated with an age-related progression of pulmonary fibrosis.
Publisher: Wiley
Date: 11-2002
Comparison of [3H]clonidine and [3H]guanfacine binding to α2 adrenoceptors in membranes from rat cerebral cortex
Publisher: Elsevier BV
Date: 08-1981
DOI: 10.1016/0304-3940(81)90096-3
Abstract: [3H]Clonidine and a new phenylacylguanidine antihypertensive drug, [3H]guanfacine, bind with a high affinity to alpha 2 adrenoceptors in membranes from rat cerebral cortex. Dissociation curves for [3H]clonidine binding indicated the presence of high and low affinity binding sites, whereas with [3H]guanfacine, two components could be distinguished only with difficulty the major part of the binding being to a high affinity component. Saturation experiments revealed that both ligands bind with similar high affinity but that [3H]guanfacine labels twice the number of sites labeled by [3H]clonidine.
Cardiac effects of relaxin in rats
Publisher: Elsevier BV
Date: 05-1992
DOI: 10.1016/0140-6736(92)90665-P
Abstract: Relaxin is usually considered to be a hormone of pregnancy, but porcine relaxin has been shown to increase heart rate in rats. We investigated the cardiac effects of synthetic human gene-2 relaxin (hRlx-2) in vitro in isolated rat atria. Synthetic hRlx-2 produced concentration-dependent positive chronotropic effects in spontaneously beating right atria (EC50 [concentration required to produce 50% of the maximal response] = 0.09 [SE 0.03] nmol/l) and concentration-dependent positive inotropic effects in electrically driven left atria (EC50 = 0.31 [0.02] nmol/l). The potency of hRlx-2 is greater than that of endothelin, angiotensin II, and (-)-isoprenaline in isolated rat atria. Relaxin has powerful chronotropic and inotropic effects on the heart that are probably mediated through a direct action on relaxin receptors.
Label-Free Kinetics: Exploiting Functional Hemi-Equilibrium to Derive Rate Constants for Muscarinic Receptor Antagonists
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 04-08-2015
Abstract: Drug receptor kinetics is as a key component in drug discovery, development, and efficacy however, determining kinetic parameters has historically required direct radiolabeling or competition with a labeled tracer. Here we present a simple approach to determining the kinetics of competitive antagonists of G protein-coupled receptors by exploiting the phenomenon of hemi-equilibrium, the state of partial re-equilibration of agonist, antagonist, and receptor in some functional assays. Using functional [Ca(2+)]i-flux and extracellular kinases 1 and 2 phosphorylation assays that have short incubation times and therefore are prone to hemi-equilibrium "behaviors," we investigated a wide range of structurally and physicochemically distinct muscarinic acetylcholine receptor antagonists. Using a combined operational and hemi-equilibrium model of antagonism to both simulate and analyze data, we derived estimates of association and dissociation rates for the test set of antagonists, identifying both rapidly dissociating (4-DAMP, himbacine) and slowly dissociating (tiotropium, glycopyrrolate) ligands. The results demonstrate the importance of assay incubation time and the degree of receptor reserve in applying the analytical model. There was an excellent correlation between estimates of antagonist pK(B), k(on), and k(off) from functional assays and those determined by competition kinetics using whole-cell [(3)H]N-methylscopolamine binding, validating this approach as a rapid and simple method to functionally profile receptor kinetics of competitive antagonists in the absence of a labeled tracer.
Changes in brainstem and spinal adrenoceptor binding with ageing in spontaneously hypertensive and Wistar-Kyoto rats
Publisher: Elsevier BV
Date: 06-1985
DOI: 10.1016/0304-3940(85)90499-9
Abstract: Adrenoceptor binding in membranes prepared from the brainstem and thoracic spinal cord of male spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats aged 6 and 36-40 weeks has been compared. Binding of [3H]prazosin (alpha 1-receptors), [3H]rauwolscine (alpha 2-receptors) and [3H]dihydroalprenolol (DHA: beta-receptors) fell with age in both regions in both strains. Strain, independent of age, was also a significant determinant of binding for all three ligands in brainstem and for [3H]DHA in spinal cord. The changes in receptor binding may reflect differences in noradrenergic activity with age and between SHR and WKY rats.
The Relaxin Family Peptide Receptor 3 Activates Extracellular Signal-Regulated Kinase 1/2 through a Protein Kinase C-Dependent Mechanism
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 09-03-2007
Abstract: Human gene 3 relaxin (H3 relaxin) is a member of the relaxin/insulin family of peptides. Neuropeptides mediate behavioral responses to stress and regulates appetite however, the cell signaling mechanisms that control these events remain to be identified. The relaxin family peptide receptor 3 (RXFP3, formerly GPCR135 or SALPR) was characterized as the receptor for H3 relaxin, functionally coupled to the inhibition of cAMP. We have identified that RXFP3 stably expressed in Chinese hamster ovary (CHO)-K1 (CHO-RXFP3) and human embryonic kidney (HEK) 293 (HEK-RXFP3) cells activates extracellular signal-regulated kinase (ERK) 1/2 when stimulated with H3 relaxin and an H3 relaxin B-chain (dimer) peptide. Using inhibitors of cellular signaling proteins, we subsequently determined the mechanism of ERK1/2 activation by RXFP3. ERK1/2 phosphorylation requires the activation of G(i/o) proteins and seems to require receptor internalization and/or compartmentalization into lipid-rich environments. ERK1/2 activation also predominantly occurred via the activation of a protein kinase C-dependent pathway, although activation of phosphatidylinositol 3-kinase and Src tyrosine kinase were also involved to a lesser extent. The mechanisms underlying ERK1/2 phosphorylation were similar in both CHO-RXFP3 and HEK-RXFP3 cells, although some differences were evident. Phospholipase Cbeta and the transactivation of endogenous epidermal growth factor receptors both played a role in RXFP3-mediated ERK1/2 activation in HEK293 cells however, they were not involved in RXFP3-mediated ERK1/2 activation in the CHO-K1 cell background. The pathways identified in CHO- and HEK-transfected cells were also used in the murine SN56 neuronal cell line, suggesting that these pathways are also important for RXFP3-mediated signaling in the brain.
Signal switching after stimulation of LGR7 receptors by human relaxin 2
Publisher: Wiley
Date: 05-2005
Abstract: Previous studies have described a biphasic cAMP response after stimulation of LGR7 by human gene 2 (H2) relaxin, involving both adenylate cyclase and PI3-kinase activity. The current study identifies the upstream involvement of Gi in the PI3-kinase-mediated response, likely the result of receptor signal switching. Amino acid sequence analysis of the LGR7 C-terminal tail and intracellular loops revealed multiple putative phosphorylation sites, suggesting that signal switching from Gs to Gi may occur after receptor phosphorylation. This study supports a time-dependent biphasic cAMP response: an initial short Gs-adenylate cyclase-mediated cAMP response is followed by receptor signal switching to a Gi-PI3-kinase-mediated response.
THE EFFECTS OF LABETALOL (AH 5158) ON ADRENERGIC TRANSMISSION IN THE CAT SPLEEN
Publisher: Wiley
Date: 04-1977
DOI: 10.1111/J.1476-5381.1977.TB07733.X
Abstract: 1. The competitive alpha- and beta-adrenoceptor blocking agent labetalol, in concentrations up to 10(-4) M, produced dose-dependent increases in transmitter overflow from the isolated blood perfused spleen of the cat following nerve stimulation at 10 and 30 Hz. 2. At concentrations above 10(-4) M labetol produced a pronounced decrease in transmitter overflow. 3. Labetalol (1.5 X 10(-4) M) increased the recovery of 3H label in the venous blood following the close-arterial infusion of [3H]-(-)-noradrenaline indicating that the drug inhibits uptake of the amine. 4. Both labetalol (3.8 X 10(-5) M) and piperoxan (7.4 X 10(-6) M) produced parallel shifts to the right of the dose-response curves to noradrenaline and oxymetazoline in isolated strips of cat splenic capsule. In this preparation both drugs acted as competitive postsynaptic alpha-adrenoceptor blocking agents. 5. Labetalol (3.3 X 10(-5) M) increased the transmitter overflow following stimulation of the splenic nerves with 200 impulses at 10 Hz. The overflow could be further increased by subsequent addition of piperoxan (7.2 X 10(-6 M). Piperoxan (5.7 X 10(-6) M) alone produced a marked increase in transmitter overflow which could be further increased by subsequent addition of desmethylimipramine (DMI 3.2 X 10(-5) M). Cocaine (1.5 X 10(-5) M) or DMI (5.4 X 10(-5 M) produced a small increase in transmitter overflow which was not further increased by addition of labetalol (2.8 X 10(-5) M). 6. Labetalol produced a biphasic effect on the responses of the isolated blood perfused spleen of the cat to nerve stimulation. With low doses (up to 10(-4) M) vascular responses were potentiated and with high doses (greater than 10(-4) M) inhibited. The potentiation was related to uptake blockade and the inhibition to decreased transmitter overflow and postsynaptic alpha-adrenoceptor blockade. 7. Labetalol appears to act as a postsynaptic alpha-adrenoceptor antagonist in the isolated blood perfused spleen of the cat with little effect on presynaptic alpha-adrenoceptors. The moderate elevation of transmitter overflow by the drug is related to the inhibitory effect of the drug on neuronal uptake rather than on presynaptic alpha-adrenoceptors.
THE CONCISE GUIDE TO PHARMACOLOGY 2017/18: Overview
Publisher: Wiley
Date: 21-10-2017
DOI: 10.1111/BPH.13882
Signal transduction pathways activated by insulin-like peptide 5 at the relaxin family peptide RXFP4 receptor.
Publisher: Wiley
Date: 13-07-2016
DOI: 10.1111/BPH.13522
Signaling pathways of the LGR7 and LGR8 receptors determined by reporter genes
Publisher: Wiley
Date: 05-2005
Abstract: Although much is known about the pleiotropic effects mediated by relaxin, the exact signaling pathways involved remain relatively elusive. This study examines LGR7 and LGR8 signaling using reporter gene technology. The greatest response was observed at the CRE reporter (indicates activation of cAMP-PKA and p38/JNK pathways), although INSL3 treatment of LGR8 produced a lower response than H2 relaxin treatment of LGR7. AP1 (which indicates activation of JNK pathways) was stimulated to a lesser degree. Three other reporters produced no response. The reporter gene studies suggest that ligand stimulation of LGR7 and LGR8 involves cAMP-PKA and p38/JNK signaling.
Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists, 1994: SIGNALLING PATHWAYS IN CARDIAC FAILURE
Publisher: Wiley
Date: 11-1995
DOI: 10.1111/J.1440-1681.1995.TB01954.X
Abstract: 1. Cardiac failure in humans and in animal models is associated with a marked desensitization of the catecholamine signalling pathway. 2. Beta 1- and beta 2- and possibly beta 3-adrenoceptors (beta-AR) are found in the hearts of humans and common laboratory animals such as rats and guinea-pigs. In rats and guinea-pigs chronic stimulation of cardiac beta-AR leads to a rapid loss of beta 2-AR whereas heart failure in humans is associated with a loss of beta 1-AR or beta 1-AR and beta 2-AR. 3. Desensitization is also associated with phosphorylation of beta-AR by beta-AR kinase (beta-ARK) and uncoupling of receptors from the signalling pathway. Beta-ARK but not beta-arrestin activity and mRNA are markedly increased in heart failure. 4. Chronic beta-AR stimulation and heart failure are associated with increases in Gi alpha but little if any change in Gs alpha. 5. The roles of beta gamma subunits of G-proteins, adenylate cyclase subtypes and cAMP dependent protein kinase A in heart failure are unclear at present. beta-ARK - beta-adrenoceptor kinase AR - adrenoceptor G-protein - GTP binding protein
Age Related Changes of Noradrenaline Content in Brain Regions of Spontaneously Hypertensive (SHR) and Normotensive Wistar-Kyoto (WK) Rats
Publisher: Informa UK Limited
Date: 1983
DOI: 10.3109/10641968309081813
Abstract: Noradrenaline (NA) was assayed in brain regions of male and female WK and SHR of 6 to 40 weeks of age, using high performance liquid chromatography with electrochemical detection (HPLC-ECD). The change of levels with age was similar in brain regions of both strains except in brainstem and thoracic spinal cord where levels fell progressively with age in SHR but not in WK rats. The fall in NA content in these two regions is associated with a rise in blood pressure with age in the SHR and suggests a relationship between NA levels and hypertension. The demonstration of different patterns of change in NA levels with age between WK and SHR represents a new approach to resolving the problem of the lack of appropriate control animals for genetic models of disease. However, the data also emphasise that differences in catecholamine metabolism may occur between in-bred strains of rat such as the WK and SHR, and between male and female rats, unrelated to differences in blood pressure.
The effect of a series of clonidine analogues on [3H] clonidine binding in rat cerebral cortex
Publisher: Elsevier BV
Date: 1979
DOI: 10.1016/0006-2952(79)90282-X
Abstract: In the microsomal fraction of Candida tropicalis cells, two distinct monooxygenases were detected, depending on the growth conditions. The distinction of the two monooxygenases was evident from: (i) the absorption maxima in the reduced CO difference spectra of the terminal oxidases (cytochromes P-450 and P-448) (ii) the contents of the monooxygenase components (cytochromes P-450/P-448, NADPH-cytochrome c (P-450) reductase, and cytochrome b5) and (iii) the catalytic activity of the complete system (aliphatic hydroxylation and N-demethylation activity). The occurrence of the respective monooxygenases could be related to the carbon source (n-alkanes or glucose). Oxygen limitation led to a significant increase of cytochrome P-450/P-448 content, independent of the carbon source utilized by the cells. An improved method for the isolation of microsomes enabled us to demonstrate the presence of cytochrome P-448 in glucose-grown cells.
The Involvement of Central Alpha Adrenoceptors in the Antihypertensive Actions of Methyldopa and Clonidine in the Rat
Publisher: Informa UK Limited
Date: 1984
DOI: 10.3109/10641968409062572
Abstract: The antihypertensive effects of methyldopa and clonidine result from agonist activity at alpha adrenoceptor sites within the brain. Methyldopa is converted enzymatically to alpha-methylnoradrenaline in noradrenergic neurones in rat brain and replaces the natural transmitter, noradrenaline. Radioligand receptor studies show that alpha-methylnoradrenaline differs from noradrenaline in being much more selective (70 times) for the alpha 2 subclass of adrenoceptors than noradrenaline and it is likely that the antihypertensive action of methyldopa results from selective activation of alpha 2 adrenoceptors by alpha-methylnoradrenaline in the nucleus tractus solitarius and the anterior hypothalamus. Radioligand studies also show that clonidine is a selective alpha 2 adrenoceptor agonist although it probably interacts with alpha 1 adrenoceptors at higher concentrations. With regard to a withdrawal syndrome after cessation of clonidine treatment, the cardiovascular and behavioural components can now be characterised in a rat model. The components include increases in basal blood pressure and heart rate, as well as increases in cardiovascular reactivity and also increases in rapid eye movement (REM) sleep, body shakes and tremor which is reminiscent of an opiate withdrawal syndrome. Increased central noradrenergic activity is involved in this syndrome and alpha 1 and alpha 2 adrenoceptors mediate opposing effects on the REM sleep rebound component.
Radioligand studies of α-adrenoceptors in the kidney
Publisher: Elsevier BV
Date: 1982
[3H]Prazosin and [3H]clonidine binding to α-adrenoceptors in membranes prepared from regions of rat kidney
Publisher: Oxford University Press (OUP)
Date: 09-1981
DOI: 10.1111/J.2042-7158.1981.TB13752.X
Abstract: Thyroid-stimulating hormone (TSH), thyroxin (T4) and T3 levels are varied in the different settings with disorders of thyroid homeostasis. It is recommended that every setting has to establish its own reference intervals (RIs) for these hormones. A multi-stage stratified s ling method was used to select a representative s le of a Sudanese adult (>20 years of age) in Nyala in western Sudan in the Darfur region during the period between January and June 2016 to establish RIs of thyroid-related hormones (TSH, T4 and T3).In this study, 1753 serum s les (male and female) with different age groups were investigated. A radioimmunoassay gamma counter was used to measure the level of these hormones. The median (95% intervals) of serum TSH, T4 and T3 levels was 1.2 (0.50-3.0) mIU/l, 111.0 (72.0-161.0) nmol/l and 1.5 (0.8-2.8) nmol/l respectively.While the level of TSH was significantly higher in the age group between 31 and 40 years, both T4 and T3 levels have shown a progressive increase with age. There was no significant difference in the TSH, T4 and T3 level when the RIs were compared between males and females. The RIs for TSH, T4 and T3 in this setting were different from the levels provided by the manufacturers. The RIs were different in the different age groups.
Differential Roles for Disulfide Bonds in the Structural Integrity and Biological Activity of κ-Bungarotoxin, a Neuronal Nicotinic Acetylcholine Receptor Antagonist
Publisher: American Chemical Society (ACS)
Date: 13-08-1998
DOI: 10.1021/BI981227Y
The PPARγ agonist rosiglitazone promotes the induction of brite adipocytes, increasing β-adrenoceptor-mediated mitochondrial function and glucose uptake
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.CELLSIG.2017.09.023
Abstract: Recruitment and activation of brite (or beige) adipocytes has been advocated as a potential avenue for manipulating whole-body energy expenditure. Despite numerous studies illustrating the differences in gene and protein markers between brown, brite and white adipocytes, there is very little information on the adrenergic regulation and function of these brite adipocytes. We have compared the functional (cyclic AMP accumulation, oxygen consumption rates, mitochondrial function, glucose uptake, extracellular acidification rates, calcium influx) profiles of mouse adipocytes cultured from three contrasting depots, namely interscapular brown adipose tissue, and inguinal or epididymal white adipose tissues, following chronic treatment with the peroxisome proliferator-activated receptor γ (PPARγ) agonist rosiglitazone. Prototypical brown adipocytes readily express β
α1A-Adrenoceptors activate mTOR signalling and glucose uptake in cardiomyocytes.
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.BCP.2017.11.016
Abstract: The capacity of G protein-coupled receptors to modulate mechanistic target of rapamycin (mTOR) activity is a newly emerging paradigm with the potential to link cell surface receptors with cell survival. Cardiomyocyte viability is linked to signalling pathways involving Akt and mTOR, as well as increased glucose uptake and utilization. Our aim was to determine whether the α
Characterization and autoradiographic localization of β‐adrenoceptor subtypes in human cardiac tissues
Publisher: Wiley
Date: 10-1987
DOI: 10.1111/J.1476-5381.1987.TB11324.X
Abstract: 1 Receptor autoradiography using (-)-[125I]-cyanopindolol (CYP) was used to study the distribution of beta-adrenoceptor subtypes in human right atrial appendage, left atrial free wall, left ventricular papillary muscle and pericardium. 2 The binding of (-)-[125I]-CYP to slide-mounted tissue sections of human right atrial appendage was time-dependent (K1 = 4.11 +/- 1.01 X 10(8) M-1 min-1, K-1 = 1.47 +/- 0.25 X 10(-3) min-1, n = 3), saturable (42.02 +/- 2.96 pM, n = 4) and stereoselective with respect to the optical isomers of propranolol (pKD (-):8.97 +/- 0.02, (+):6.88 +/- 0.06, n = 3). 3 The proportions of beta-adrenoceptor subtypes were determined in slide-mounted tissue sections using the antagonists CGP 20712A (beta 1-selective) and ICI 118,551 (beta 2-selective). In right atrial appendage and left ventricular papillary muscle 40% (34-45%) of the beta-adrenoceptors were of the beta 2-subtype. 4 Images from X-ray film and nuclear emulsion coated coverslips exposed to (-)-[125I]-CYP-labelled sections showed an even distribution of beta-adrenoceptor subtypes over the myocardium of the right atrial appendage, left ventricular papillary muscle and left atrial free wall. Sections of pericardium exhibited predominantly beta 2-adrenoceptors. beta 2-Adrenoceptors were localized to the intimal surface of coronary arteries. 5 The selective beta 1-adrenoceptor agonist RO363 and beta 2-selective agonist procaterol produced concentration-dependent inotropic responses in right atrial appendage strips. Responses to RO363 were antagonized by CGP 20712A (pKB = 9.29) suggesting an interaction with beta 1-adrenoceptors. Responses to procaterol were antagonized by ICI 118,551 (pKB = 9.06) suggesting an interaction at beta 2-adrenoceptors. 6 The finding that a significant proportion of human myocardial adrenoceptors are of the beta 2-subtype has important clinical implications for the involvement of these receptors in the control of heart rate and force, and the autoradiographic evidence suggests other roles in the coronary vasculature and pericardium.
Characterization of the β‐adrenoceptor subtype involved in mediation of glucose transport in L6 cells
Publisher: Wiley
Date: 09-2002
Desensitization of cardiac β-adrenoceptor signaling with heart failure produced by myocardial infarction in the rat. Evidence for the role of Gi but not Gs or phosphorylating proteins
Publisher: Elsevier BV
Date: 06-1999
Evidence from binding studies for β1-adrenoceptors associated with glomeruli isolated from rat kidney
Publisher: Elsevier BV
Date: 07-1983
DOI: 10.1016/0024-3205(83)90715-4
Abstract: The beta adrenoceptor antagonist radioligand [3H] dihydroalprenolol (DHA) has been used to characterise beta adrenoceptors in membranes prepared from rat renal glomeruli. Association of the ligand was rapid and had reached equilibrium within 10 mins at 37 degrees C. Dissociation occurred in two distinct phases, a rapidly dissociating phase (low affinity site) and a slowly dissociating phase (high affinity site). The KD value for the high affinity site calculated from the kinetic experiments was 0.8 nM. Saturation analysis of binding gave comparable values for KD (1.77 nM) and demonstrated that membranes from glomeruli had four times the density of binding sites measured in renal cortex. In all saturation studies Hill coefficients were not significantly different from unity. Binding was stereoselective with respect to the (-) isomers of isoprenaline and propranolol and the potency of the selective displacing agents betaxolol (beta 1 adrenoceptors) and ICI 118,551 (beta 2 adrenoceptors) indicated that the receptors are of the beta 1 subtype.
Relaxin family peptides and their receptors
Publisher: American Physiological Society
Date: 2013
DOI: 10.1152/PHYSREV.00001.2012
Abstract: There are seven relaxin family peptides that are all structurally related to insulin. Relaxin has many roles in female and male reproduction, as a neuropeptide in the central nervous system, as a vasodilator and cardiac stimulant in the cardiovascular system, and as an antifibrotic agent. Insulin-like peptide-3 (INSL3) has clearly defined specialist roles in male and female reproduction, relaxin-3 is primarily a neuropeptide involved in stress and metabolic control, and INSL5 is widely distributed particularly in the gastrointestinal tract. Although they are structurally related to insulin, the relaxin family peptides produce their physiological effects by activating a group of four G protein-coupled receptors (GPCRs), relaxin family peptide receptors 1–4 (RXFP1–4). Relaxin and INSL3 are the cognate ligands for RXFP1 and RXFP2, respectively, that are leucine-rich repeat containing GPCRs. RXFP1 activates a wide spectrum of signaling pathways to generate second messengers that include cAMP and nitric oxide, whereas RXFP2 activates a subset of these pathways. Relaxin-3 and INSL5 are the cognate ligands for RXFP3 and RXFP4 that are closely related to small peptide receptors that when activated inhibit cAMP production and activate MAP kinases. Although there are still many unanswered questions regarding the mode of action of relaxin family peptides, it is clear that they have important physiological roles that could be exploited for therapeutic benefit.
Responses of GPCR135 to human gene 3 (H3) relaxin in CHO-K1 cells determined by microphysiometry
Publisher: Wiley
Date: 05-2005
Abstract: This study examined the functional response to human relaxin 2 (H2 relaxin), human relaxin 3 (H3 relaxin), porcine relaxin, and human INSL3 in the cytosensor microphysiometer, using CHO-K1 cells stably expressing human GPCR135. CHO-K1 cells stably expressing GPCR135 were generated by the serial dilution method and receptor properties were assessed. Saturation studies of [125I] H3 relaxin binding to GPCR135 in these cells gave a Bmax of 32.61 +/- 6.5 fmol/mg protein and Kd of 0.12 +/- 0.08 nM. The functional response to H3 relaxin and other relaxin/insulin peptides of GPCR135 expressed in CHO-K1 cells was measured in the cytosensor microphysiometer and analyzed using inhibitors of signal transduction proteins.
Relaxin inhibits renal myofibroblast differentiation via RXFP1, the nitric oxide pathway, and Smad2
Publisher: Wiley
Date: 10-12-2009
DOI: 10.1096/FJ.08-120857
Abstract: The hormone relaxin inhibits renal myofibroblast differentiation by interfering with TGF-beta1/Smad2 signaling. However, the pathways involved in the relaxin-TGF-beta1/Smad2 interaction remain unknown. This study investigated the signaling mechanisms by which human gene-2 (H2) relaxin regulates myofibroblast differentiation in vitro by examining its effects on mixed populations of fibroblasts and myofibroblasts propagated from injured rat kidneys. Cultures containing approximately 60-70% myofibroblasts were used to determine which relaxin receptors, G-proteins, and signaling pathways were involved in the H2 relaxin-mediated regulation of alpha-smooth muscle actin (alpha-SMA a marker of myofibroblast differentiation). H2 relaxin only inhibited alpha-SMA immunostaining and collagen concentration in the presence of relaxin family peptide receptor 1 (RXFP1). H2 relaxin also induced a transient rise in cAMP in the presence of G(i/o) inhibition, and a sustained increase in extracellular signal-regulated kinase (ERK)-1/2 phosphorylation. Furthermore, inhibition of neuronal nitric oxide synthase (nNOS), NO, and cGMP significantly blocked the inhibitory effects of relaxin on alpha-SMA and Smad2 phosphorylation, while the NO inhibitor, L-nitroarginine methyl ester (hydrochloride) (L-NAME) significantly blocked the inhibitory actions of relaxin on collagen concentration in vivo. These findings suggest that relaxin signals through RXFP1, and a nNOS-NO-cGMP-dependent pathway to inhibit Smad2 phosphorylation and interfere with TGF-beta1-mediated renal myofibroblast differentiation and collagen production.
Importance of adrenergic receptors in prenatally induced cognitive impairment in the domestic chick.
Publisher: Wiley
Date: 05-11-2009
DOI: 10.1016/J.IJDEVNEU.2008.10.005
Abstract: In the domestic chick, mild hypoxia (24h of 14% oxygen) at two stages of embryonic development results in post-hatch memory deficiencies tested using a discriminated bead avoidance task. The nature of the memory loss depends on the gestational age at which the hypoxia occurs. Hypoxia on embryonic day 10 (E10) of a 21 day incubation results in chicks with no short-term memory 10 min after training, whereas hypoxia on day 14 (E14) results in chicks with good labile memory 30 min after training but no consolidation of memory into permanent storage (120 min). Hypoxia at E14 is associated with increased plasma levels of noradrenaline and therefore we suggest that altered catecholamine exposure within the brain contributes to cognitive problems by modifying the responsiveness of brain beta-adrenoceptors. In ovo administration of noradrenaline, or the beta(2)-adrenoceptor agonist formoterol, at E14 had the same effect on memory consolidation as hypoxia. Following hypoxia at E14, memory could be rescued after training by central injection of a beta(3)-adrenoceptor agonist, but not by a beta(2)-adrenoceptor agonist. The differences in the responsiveness of memory processing to beta(2)-adrenoceptor agonists suggests alterations to the receptors or downstream of the receptor activation. However, both types of beta-adrenoceptor agonists rescued memory in E10 treated chicks implying that at this age hypoxia does not affect the receptors. In summary, hypoxia or increased levels of stress hormones during incubation alters beta-adrenoceptor responsiveness the outcome of the insult depends upon the cellular developmental processes at a given embryonic stage.
Recent progress in the understanding of relaxin family peptides and their receptors
Publisher: Wiley
Date: 26-04-2017
DOI: 10.1111/BPH.13778
The distribution of β-adrenoceptors in dog kidney: an autoradiographic analysis
Publisher: Elsevier BV
Date: 08-1987
DOI: 10.1016/0014-2999(87)90627-3
Abstract: The distribution of beta-adrenoceptors in slide-mounted dog kidney sections was determined using the radioligand (-)-[125I]cyanopindolol ((-)-[125I]CYP) and autoradiography. Using conditions designed to prevent (-)-[125I]CYP binding to non-beta-adrenoceptor sites, biochemical studies revealed that (-)-[125I]CYP binding equilibrated within 150 min (K1 = 3.2 X 10(8) M-1 min-1), was saturable (KD = 30.72 +/- 2.96 pM Bmax = 0.57 +/- 0.03 fmol/section, n = 4) and stereoselective with respect to the stereoisomers of propranolol and pindolol. Delineation of beta-adrenoceptor subtypes with the selective beta 1-adrenoceptor antagonist betaxolol and beta 2-adrenoceptor antagonist ICI 118,551 demonstrated that the proportions of beta 1-: beta 2-adrenoceptors was between 1:6 and 1:11. Autoradiographic studies showed that beta 1-adrenoceptors were localized on the juxtaglomerular apparatus and glomeruli, while beta 2-adrenoceptors were localized on medullary rays. The distribution of beta-adrenoceptors with respect to renal function in the dog kidney is discussed.
Quantitative autoradiographic studies of relaxin binding in rat atria, uterus and cerebral cortex: characterization and effects of oestrogen treatment
Publisher: Wiley
Date: 05-1999
NEW TOOLS FOR THE LOCALIZATION OF SECOND MESSENGER SYSTEMS
Publisher: Wiley
Date: 06-1989
DOI: 10.1111/J.1440-1681.1989.TB01604.X
Abstract: 1. Probes available for the localization of components of second messenger systems include G-protein oligonucleotides which have been used to produce cDNA probes to label G-protein mRNA by in situ hybridization histochemistry. 2. Enzymes involved in second messenger responses have been labelled with [3H]-forskolin (Gs-linked adenylate cyclase), [3H]-cAMP (cAMP-dependent protein kinase) and [3H]-PDBu2 (protein kinase C). 3. [3H]-Inositol 1,4,5 trisphosphate labels a site on sarcoplasmic reticulum believed to trigger Ca2+ release. 4. These probes allow the comparison of location of receptors and second messengers and the examination of changes in second messenger systems with drug treatment and disease.
β-Adrenoceptor regulation and functional responses in the guinea-pig following chronic administration of the long-acting β2 -adrenoceptor agonist formoterol
Publisher: Springer Science and Business Media LLC
Date: 06-1995
DOI: 10.1007/BF00170156
[3H]‐rauwolscine binding to α2‐adrenoceptors in the mammalian kidney: apparent receptor heterogeneity between species
Publisher: Wiley
Date: 06-1985
DOI: 10.1111/J.1476-5381.1985.TB08868.X
Abstract: Binding of the alpha 2-adrenoceptor antagonist [3H]-rauwolscine was characterized in membrane preparations from the kidneys of mouse, rat, rabbit, dog, and man. In all species, binding reached equilibrium within 45 min and dissociated at a single exponential rate after addition of phentolamine 10 microM. Saturation studies showed that the affinity of [3H]-rauwolscine was similar in all species (2.33-3.03 nM) except man where it was significantly higher (0.98 nM). Marked differences were seen in the density of binding sites, increasing in the order: man less than dog less than rabbit less than rat less than mouse. In all cases, Hill coefficients were not significantly different from unity. [3H]-rauwolscine binds with low affinity (KD greater than 15 nM) to membranes prepared from guinea-pig kidney. The low affinity binding is not due to the absence of particular ions in the incubation medium or to receptor occupation by endogenous agonist. The binding in all species was found to be stereoselective with respect to the isomers of noradrenaline. However, differences were seen in the characteristics of agonist interactions with the binding site both between isomers and between species. Marked differences in affinity of particular alpha-adrenoceptor antagonists were observed for alpha 2-adrenoceptors labelled by [3H]-rauwolscine. These differences were most evident with the alpha 1-adrenoceptor selective antagonist prazosin which displayed inhibition constants (Ki values) of 33.2, 39.5, 261, 570 and 595 nM in rat, mouse, dog, man and rabbit, respectively. Differences are apparent in the characteristics of alpha 2-adrenoceptors labelled by [3H]-rauwolscine between species and it is suggested that the differences observed for alpha 1-selective antagonists such as prazosin may be related to binding to additional sites in the vicinity of the alpha 2-adrenoceptor.
Localization of (-)-[125I]cyanopindolol binding in guinea-pig heart: characteristics of non-β-adrenoceptor related binding in cardiac pacemaker and conducting regions
Publisher: Elsevier BV
Date: 02-1992
DOI: 10.1016/0304-3940(92)90662-Q
Abstract: Receptor autoradiography was used in guinea-pig heart to locate binding sites for the beta-adrenoceptor ligand (-)[125I]cyanopindolol (CYP) resistant to blockade by the beta-adrenoceptor antagonist (-)-propranolol (1 microM). Highly localized binding was observed to regions closely associated with the sinoatrial node, atrioventricular node and bundle of His but was not observed on myocardial, pacemaker, conducting cells or adipose tissue. Free [125I] also bound to identical sites. Binding was enhanced in the presence of ascorbic acid but was completely inhibited by (-)-isoprenaline (100 microM), serotonin (5-HT) (10 microM) and phentolamine (10 microM).
Effect of chemical sympathectomy on (−)‐isoprenaline‐induced changes in cardiac β‐adrenoceptor subtypes in the guinea‐pig and rat
Publisher: Wiley
Date: 12-1994
DOI: 10.1111/J.1474-8673.1994.TB00622.X
Abstract: 1. Quantitative autoradiography was used to determine beta-adrenoceptor densities in cardiac regions of guinea-pigs and rats after chemical sympathectomy with 6-hydroxydopamine, and to examine how chemical sympathectomy affected beta-adrenoceptor changes following infusion of (-)-isoprenaline (400 micrograms kg-1 hr-1, 7 days). 2. Seven days after 6-hydroxydopamine (100 mg kg-1, i.v.), cardiac tissue levels of noradrenaline were reduced by 94.0 +/- 3.5% (guinea-pig) and 86.0 +/- 7.0% (rat). The blood pressure increase in rats to tyramine (0.5 mg, i.v.) was reduced from 118 mmHg in controls to 4.4 mmHg in 6-hydroxydopamine-treated animals. 3. There were no changes 7 and 14 days after 6-hydroxydopamine treatment in total, beta 1-and beta 2-adrenoceptor density in the atrioventricular conducting system and atrial and ventricular myocardium in both species. 4. In control animals, (-)-isoprenaline infusion produced selective reductions in beta 2-adrenoceptor density, whilst beta 1-adrenoceptor density remained unchanged. 5. In 6-hydroxydopamine treated guinea-pigs or rats, (-)-isoprenaline infusion caused no change in beta 1-adrenoceptors except in the right bundle branch whilst beta 2-adrenoceptors were reduced in the atrioventricular conducting system (atrioventricular node, bundle of His, right and left bundle branches) and myocardium (interventricular septum and atria). 6. The differential effect of (-)-isoprenaline on beta 1- and beta 2-adrenoceptors is not therefore due to the occupation of beta 1-adrenoceptors by noradrenaline or to prior down-regulation of beta 1-adrenoceptors by noradrenaline, since it persists after depletion of noradrenaline.
Ligand-directed signalling at beta-adrenoceptors.
Publisher: Wiley
Date: 03-2010
α₂-Adrenoceptors activate noradrenaline-mediated glycogen turnover in chick astrocytes.
Publisher: Wiley
Date: 26-04-2011
DOI: 10.1111/J.1471-4159.2011.07261.X
Abstract: In the brain, glycogen is primarily stored in astrocytes where it is regulated by several hormones/neurotransmitters, including noradrenaline that controls glycogen breakdown (in the short term) and synthesis. Here, we have examined the adrenoceptor (AR) subtype that mediates the glycogenic effect of noradrenaline in chick primary astrocytes by the measurement of glycogen turnover (total (14) C incorporation of glucose into glycogen) following noradrenergic activation. Noradrenaline and insulin increased glycogen turnover in a concentration-dependent manner. The effect of noradrenaline was mimicked by stimulation of α(2) -ARs (and to a lesser degree by β(3) -ARs), but not by stimulation of α(1) -, β(1) -, or β(2) -ARs, and occurred only in astrocytes and not neurons. In chick astrocytes, studies using RT-PCR and radioligand binding showed that α(2A) - and α(2C) -AR mRNA and protein were present. α(2) -AR- or insulin-mediated glycogen turnover was inhibited by phosphatidylinositol-3 kinase inhibitors, and both insulin and clonidine caused phosphorylation of Akt and glycogen synthase kinase-3 in chick astrocytes. α(2) -AR but not insulin-mediated glycogen turnover was inhibited by pertussis toxin pre-treatment indicating involvement of Gi/o proteins. These results show that the increase in glycogen turnover caused by noradrenaline is because of activation of α(2) -ARs that increase glycogen turnover in astrocytes utilizing a Gi/o-PI3K pathway.
Inhibition of phenylephrine‐stimulated gluconeogenesis by chlorpromazine is mediated by α‐adrenergic receptors
Publisher: Wiley
Date: 20-04-1981
DOI: 10.1016/0014-5793(81)80269-4
Abstract: We report on direct, real-space imaging of the stray magnetic field above a micro-scale disc of a thin film of the high-temperature superconductor YBa₂Cu₃O
CHARACTERIZATION AND LOCALIZATION OF (—‐)[125I]‐CYANOPINDOLOL BINDING TO NON‐β‐ADRENOCEPTOR SITES IN DOG KIDNEY
Publisher: Wiley
Date: 09-1987
DOI: 10.1111/J.1440-1681.1987.TB01896.X
Abstract: 1. (-)[125I]-Cyanopindolol (CYP) binding to non-beta-adrenoceptor sites in dog kidney was characterized in homogenate preparations and their distribution in sections determined using autoradiography. 2. In homogenate studies, (-)[125I]-CYP bound to a single population of non-interacting sites (Bmax = 5.45, s.e.m. = 1.00 fmol/mg wet weight nH = 0.99, s.e.m. = 0.01) with high affinity (KD = 3.84, s.e.m. = 0.76 nmol/l, n = 40. 3. In competition studies, compounds selective for alpha- and beta-adrenoceptors, muscarinic cholinoceptors and receptors for 5-HT, histamine and benzodiazepines, calcium channel antagonists, catecholamine uptake inhibitors, MAO inhibitors and adrenergic neurone blockers were ineffective at concentrations of 10 mumol/l. 4. Compounds selective for dopamine D1-receptors (fluphenazine, SCH 23390 and SK & F 82526) and D2-receptors (pimozide, domperidone, spiperone, haloperidol, sulpiride, cis- and trans-flupenthixol) competed with similar affinities (5-25 mumol/l) for (-)[125I]-CYP binding. 5. In autoradiographic studies, (-)[125I]-CYP binding to non-beta-adrenoceptor sites was localized over glomeruli, juxtaglomerular apparatus, distal tubules, blood vessels and medullary rays and tubules. 6. It is concluded that in dog kidney, (-)[125I]-CYP binds to a site closely associated with dopamine receptors.
beta(3)-adrenoceptor regulation and relaxation responses in mouse ileum.
Publisher: Wiley
Date: 03-2000
Regulation of β-adrenoceptors in a rat model of cardiac failure: Effect of perindopril
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-1998
DOI: 10.1097/00005344-199807000-00011
Abstract: This study investigated the effects of myocardial infarction (MI)-induced cardiac failure and treatment with an angiotensin-converting enzyme (ACE) inhibitor perindopril (2 mg/kg/day) on rat beta-adrenoceptor (beta-ar) subtypes in anatomically defined regions of infarcted left ventricular (LV) free wall and noninfarcted tissue from right ventricle (RV) by using autoradiography. After 5 weeks of MI, rats with large MI size (>42%) had developed cardiac failure and beta1-ars were significantly decreased (-59% p < 0.01) in the border region of the infarcted LV and almost abolished in the infarcted area (-90% p < 0.005) compared with normal LV from sham-operated controls. The beta-ar changes were not found in the noninfarcted area of the same LV or in RV. MI did not significantly alter the number of beta2-ar subtypes in any region of the ventricles. Perindopril treatment for 4 weeks reduced mean cardiac region weights but did not affect beta-ar density in any cardiac region in either sham-operated or MI rats. These results indicate that cardiac failure due to MI causes significant downregulation of beta1-ars only in border and infarcted regions of rat LV and no change in beta2-ar in any area. It also suggests that the improved response of the infarcted rat heart to isoprenaline stimulation after ACE inhibitors does not result from changes in the numbers of cardiac beta-ars.
The M3-muscarinic acetylcholine receptor stimulates glucose uptake in L6 skeletal muscle cells by a CaMKK-AMPK-dependent mechanism
Publisher: Elsevier BV
Date: 07-2010
DOI: 10.1016/J.CELLSIG.2010.03.004
Abstract: The role of muscarinic acetylcholine receptors (mAChRs) in regulating glucose uptake in L6 skeletal muscle cells was investigated. [(3)H]-2-Deoxyglucose uptake was increased in differentiated L6 cells by insulin, acetylcholine, oxotremorine-M and carbachol. mAChR-mediated glucose uptake was inhibited by the AMPK inhibitor Compound C. Whole cell radioligand binding using [(3)H]-N-methyl scopolamine chloride identified mAChRs in differentiated but not undifferentiated L6 cells and M(3) mAChR mRNA was detected only in differentiated cells. M(3) mAChRs are Gq-coupled, and cholinergic stimulation by the mAChR agonists acetylcholine, oxotremorine-M and carbachol increased Ca(2+) in differentiated but not undifferentiated L6 cells. This was due to muscarinic but not nicotinic activation as responses were antagonised by the muscarinic antagonist atropine but not the nicotinic antagonist tubocurarine. Western blotting showed that both carbachol and the AMPK activator AICAR increased phosphorylation of the AMPKalpha subunit at Thr172, with responses to carbachol blocked by Compound C and the CaMKK inhibitor STO609 but not by the PI3K inhibitor wortmannin. AICAR-stimulated AMPK phosphorylation was not sensitive to STO-609, confirming that this compound inhibits CaMKK but not the classical AMPK kinase LKB1. The TAK1 inhibitor (5Z)-7-oxozeaenol and the G(i) inhibitor pertussis toxin both failed to block AMPK phosphorylation in response to carbachol. Using CHO-K1 cells stably expressing each of the mAChR subtypes (M(1)-M(4)), it was determined that only the M(1) and M(3) mAChRs phosphorylate AMPK, confirming a G(q)-dependent mechanism. This study demonstrates that activation of M(3) mAChRs in L6 skeletal muscle cells stimulates glucose uptake via a CaMKK-AMPK-dependent mechanism, independent of the insulin-stimulated pathway.
Functional domains of the mouse beta(3)-adrenoceptor associated with differential G-protein coupling.
Publisher: Portland Press Ltd.
Date: 10-2007
DOI: 10.1042/BST0351035
Investigations into the inhibitory effects of relaxin on renal myofibroblast differentiation
Publisher: Wiley
Date: 04-2009
DOI: 10.1111/J.1749-6632.2008.03823.X
Abstract: Derived from fibroblasts, myofibroblasts are the principal cells that are responsible for the synthesis and reorganization of excess matrix in renal interstitial fibrosis. Recognized from their de novo expression of alpha-smooth muscle actin, myofibroblast differentiation and activity can be influenced by several factors, including a combination of growth factors and other soluble mediators, extracellular matrix components, and mechanical stress. Relaxin has previously been shown to inhibit renal myofibroblast differentiation in vitro, an effect partly mediated through its ability to interfere with the transforming growth factor-beta1 (TGF-beta1) pathway via inhibition of Smad2 phosphorylation and translocation. Furthermore, endogenous relaxin has been shown to protect the kidney from a myofibroblast-mediated model of injury in vivo. However, the pathways involved in the interaction between relaxin and TGF-beta1 remain unknown. In this report, the inhibitory actions of relaxin on TGF-beta1-induced renal myofibroblast differentiation are summarized to date, and the potential signaling pathways that are implicated in relaxin's inhibitory actions are discussed.
The actions of relaxin on the human cardiovascular system
Publisher: Wiley
Date: 11-07-2016
DOI: 10.1111/BPH.13523
'Relaxin' the stiffened heart and arteries: The therapeutic potential for relaxin in the treatment of cardiovascular disease
Publisher: Elsevier BV
Date: 11-2006
DOI: 10.1016/J.PHARMTHERA.2005.05.012
Abstract: Although originally characterised as a reproductive hormone, relaxin has emerged as a multi-functional endocrine and paracrine factor that plays a number of important roles in several organs, including the normal and diseased cardiovascular system. The recent discovery of the H3/relaxin-3 gene, and the elusive receptors for relaxin (Relaxin family peptide receptor RXFP1) and relaxin-3 (RXFP3/RXFP4) have led to the re-classification of a distinct relaxin peptide/receptor family. Additionally, the identification of relaxin and RXFP1 mRNA and/or relaxin binding sites in the heart and blood vessels has confirmed that the cardiovascular system is a target for relaxin peptides. While evidence for the production of relaxins within the cardiovascular system is limited, several studies have established that the relaxin genes are upregulated in the diseased human and rodent heart where they likely act as cardioprotective agents. The ability of relaxin to protect the heart is most likely mediated via its antifibrotic, anti-hypertrophic, anti-inflammatory and vasodilatory actions, but it may also directly stimulate myocardial regeneration and repair. This review describes relaxin and its primary receptor (RXFP1) in relation to the roles and effects of relaxin in the normal and pathological cardiovascular system. It is becoming increasingly clear that relaxin has a number of erse physiological and pathological roles in the cardiovascular system that may have important therapeutic and clinical implications.
Increase of fat oxidation and weight loss in obese mice caused by chronic treatment with human growth hormone or a modified C-terminal fragment
Publisher: Springer Science and Business Media LLC
Date: 10-2001
Abstract: To observe the chronic effects of human growth hormone (hGH) and AOD9604 (a C-terminal fragment of hGH) on body weight, energy balance, and substrate oxidation rates in obese (ob/ob) and lean C57BL/6Jmice. In vitro assays were used to confirm whether the effects of AOD9604 are mediated through the hGH receptor, and if this peptide is capable of cell proliferation via the hGH receptor. Obese and lean mice were treated with hGH, AOD or saline for 14 days using mini-osmotic pumps. Body weight, caloric intake, resting energy expenditure, fat oxidation, glucose oxidation, and plasma glucose, insulin and glycerol were measured before and after treatment. BaF-BO3 cells transfected with the hGH receptor were used to measure in vitro 125I-hGH receptor binding and cell proliferation. Both hGH and AOD significantly reduced body weight gain in obese mice. This was associated with increased in vivo fat oxidation and increased plasma glycerol levels (an index of lipolysis). Unlike hGH, however, AOD9604 did not induce hyperglycaemia or reduce insulin secretion. AOD9604 does not compete for the hGH receptor and nor does it induce cell proliferation, unlike hGH. Both hGH and its C-terminal fragment reduce body weight gain, increase fat oxidation, and stimulate lipolysis in obese mice, yet AOD9604 does not interact with the hGH receptor. Thus, the concept of hGH behaving as a pro-hormone is further confirmed. This data shows that fragments of hGH can act in a manner novel to traditional hGH-stimulated pathways.
Tissue functions mediated by β3-adrenoceptors—findings and challenges
Publisher: Springer Science and Business Media LLC
Date: 03-06-2010
International union of pharmacology LVII: Recommendations for the nomenclature of receptors for relaxin family peptides
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 28-02-2006
DOI: 10.1124/PR.58.1.9
Abstract: Although the hormone relaxin was discovered 80 years ago, only in the past 5 years have the receptors for relaxin and three other receptors that respond to related peptides been identified with all four receptors being G-protein-coupled receptors. In this review it is suggested that the receptors for relaxin (LGR7) and those for the related peptides insulin-like peptide 3 (LGR8), relaxin-3 (GPCR135), and insulin-like peptide 5 (LGPCR142) be named the relaxin family peptide receptors 1 through 4 (RXFP1-4). RXFP1 and RXFP2 are leucine-rich repeat-containing G-protein-coupled receptors with complex binding characteristics involving both the large ectodomain and the transmembrane loops. RXFP1 activates adenylate cyclase, protein kinase A, protein kinase C, phosphatidylinositol 3-kinase, and extracellular signaling regulated kinase (Erk1/2) and also interacts with nitric oxide signaling. RXFP2 activates adenylate cyclase in recombinant systems, but physiological responses are sensitive to pertussis toxin. RXFP3 and RXFP4 resemble more conventional peptide liganded receptors and both inhibit adenylate cyclase, and in addition RXFP3 activates Erk1/2 signaling. Physiological studies and examination of the phenotypes of transgenic mice have established that relaxin has roles as a reproductive hormone involved in uterine relaxation (some species), reproductive tissue growth, and collagen remodeling but also in the cardiovascular and renal systems and in the brain. The connective tissue remodeling properties of relaxin acting at RXFP1 receptors have potential for the development of agents effective for the treatment of cardiac and renal fibrosis, asthma, and scleroderma and for orthodontic remodelling. Agents acting at RXFP2 receptors may be useful for the treatment of cryptorchidism and infertility, whereas antagonists may be used as contraceptives. The brain distribution of RXFP3 receptors suggests that actions at these receptors have the potential for the development of antianxiety and antiobesity drugs.
Drug-receptor kinetics and sigma-1 receptor affinity differentiate clinically evaluated histamine H3 receptor antagonists
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.NEUROPHARM.2018.10.028
Abstract: The histamine H
INSL5 activates multiple signalling pathways and regulates GLP-1 secretion in NCI-H716 cells.
Publisher: Bioscientifica
Date: 04-2018
DOI: 10.1530/JME-17-0152
Abstract: Insulin-like peptide 5 (INSL5) is a newly discovered gut hormone expressed in colonic enteroendocrine L-cells but little is known about its biological function. Here, we show using RT-qPCR and in situ hybridisation that Insl5 mRNA is highly expressed in the mouse colonic mucosa, colocalised with proglucagon immunoreactivity. In comparison, mRNA for RXFP4 (the cognate receptor for INSL5) is expressed in various mouse tissues, including the intestinal tract. We show that the human enteroendocrine L-cell model NCI-H716 cell line, and goblet-like colorectal cell lines SW1463 and LS513 endogenously express RXFP4. Stimulation of NCI-H716 cells with INSL5 produced phosphorylation of ERK1/2 (Thr 202 /Tyr 204 ), AKT (Thr 308 and Ser 473 ) and S6RP (Ser 235/236 ) and inhibited cAMP production but did not stimulate Ca 2+ release. Acute INSL5 treatment had no effect on GLP-1 secretion mediated by carbachol or insulin, but modestly inhibited forskolin-stimulated GLP-1 secretion in NCI-H716 cells. However, chronic INSL5 pre-treatment (18 h) increased basal GLP-1 secretion and prevented the inhibitory effect of acute INSL5 administration. LS513 cells were found to be unresponsive to INSL5 despite expressing RXFP4 . Another enteroendocrine L-cell model, mouse GLUTag cells did not express detectable levels of Rxfp4 and were unresponsive to INSL5. This study provides novel insights into possible autocrine aracrine roles of INSL5 in the intestinal tract.
β(2)-Adrenoceptors increase translocation of GLUT4 via GPCR kinase sites in the receptor C-terminal tail.
Publisher: Wiley
Date: 10-02-2012
The Effects of Human GH and Its Lipolytic Fragment (AOD9604) on Lipid Metabolism Following Chronic Treatment in Obese Mice andβ 3-AR Knock-Out Mice
Publisher: The Endocrine Society
Date: 12-2001
Abstract: Both human GH (hGH) and a lipolytic fragment (AOD9604) synthesized from its C-terminus are capable of inducing weight loss and increasing lipolytic sensitivity following long-term treatment in mice. One mechanism by which this may occur is through an interaction with the beta-adrenergic pathway, particularly with the beta(3)-adrenergic receptors (beta(3)-AR). Here we describe how hGH and AOD9604 can reduce body weight and body fat in obese mice following 14 d of chronic ip administration. These results correlate with increases in the level of expression of beta(3)-AR RNA, the major lipolytic receptor found in fat cells. Importantly, both hGH and AOD9604 are capable of increasing the repressed levels of beta(3)-AR RNA in obese mice to levels comparable with those in lean mice. The importance of beta(3)-AR was verified when long-term treatment with hGH and AOD9604 in beta(3)-AR knock-out mice failed to produce the change in body weight and increase in lipolysis that was observed in wild-type control mice. However, in an acute experiment, AOD9604 was capable of increasing energy expenditure and fat oxidation in the beta(3)-AR knock-out mice. In conclusion, this study demonstrates that the lipolytic actions of both hGH and AOD9604 are not mediated directly through the beta(3)-AR although both compounds increase beta(3)-AR expression, which may subsequently contribute to enhanced lipolytic sensitivity.
Interaction with caveolin-1 modulates G protein coupling of mouse β3-adrenoceptor.
Publisher: Elsevier BV
Date: 06-2012
Stereoselectivity for interactions of agonists and antagonists at mouse, rat and human beta3-adrenoceptors.
Publisher: Elsevier BV
Date: 2004
DOI: 10.1016/J.EJPHAR.2003.11.034
Abstract: This study examines the stereoselectivity profile of recombinant mouse, rat and human beta(3)-adrenoceptors expressed in Chinese Hamster Ovary (CHO-K1) cells using radioligand binding, in comparison with endogenously expressed beta(3)-adrenoceptors mediating relaxation responses in mouse ileum. The enantiomeric ratios for several beta-adrenoceptor agonists and antagonists at the cloned mouse, rat and human beta(3)-adrenoceptor were less than those reported at the cloned beta(1)-/beta(2)-adrenoceptor but higher than those reported in previous studies. The degree of stereoselectivity was relatively low for the agonists isoprenaline and noradrenaline but higher for antagonists and, in particular, tertatolol and propranolol. In mouse ileum, stereoselectivity of propranolol and tertatolol was observed under beta(1)-/beta(2)-adrenoceptor blockade. The (-)-enantiomers of propranolol and tertatolol were more effective at antagonism of (-)-isoprenaline-mediated relaxation of mouse ileum than their (+)-enantiomers. The recombinant mouse, rat and human beta(3)-adrenoceptors display stereoselective interactions for agonists and antagonists similar to the stereoselective profile of beta(3)-adrenoceptors in mouse ileum. The degree of stereoselectivity varied between species and the human beta(3)-adrenoceptor displayed higher affinities and enantiomeric ratios than the mouse or rat beta(3)-adrenoceptors.
G Protein–Coupled Receptors Targeting Insulin Resistance, Obesity, and Type 2 Diabetes Mellitus
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 12-12-2017
Abstract: G protein-coupled receptors (GPCRs) continue to be important discovery targets for the treatment of type 2 diabetes mellitus (T2DM). Many GPCRs are directly involved in the development of insulin resistance and
Anticonvulsant effects of clonidine mediated through central α2-adrenoceptors
Publisher: Elsevier BV
Date: 1982
DOI: 10.1016/0014-2999(82)90013-9
Abstract: The effects of centrally (0.3-30 ng/kg) and peripherally (0.01 microgram/kg-1.0 mg/kg) administered clonidine on PTZ-induced seizures was studied in rats. At low doses, dose-dependent decreases in the duration of seizures was observed but at higher doses the duration returned to control levels. Anticonvulsant activity was antagonized by yohimbine (100 microgram/kg i.p.) indicating alpha2-adrenoceptor involvement, whereas the second phase of the response was antagonized by prazosin (10 ng/kg i.c.v.) indicating that it involved alpha1-adrenoceptors.
RXFP1 couples to the Gαi3-Gβγ-PI3K-PKCζ pathway via the final 10 amino acids of the receptor C-terminal tail
Publisher: Wiley
Date: 04-2009
DOI: 10.1111/J.1749-6632.2008.03813.X
Abstract: The relaxin family peptide receptors RXFP1 and RXFP2 are highly similar receptors that share approximately 80% amino acid sequence homology. Constitutively active receptors couple to increased cAMP accumulation, which is important for relaxin-mediated decidualization and myometrial inhibition. Despite the high homology, the receptors couple to different G-proteins to affect cAMP accumulation. This study aimed to determine the region of RXFP1 that directs coupling to the delayed Galpha(i3) pathway by using receptor mutagenesis. Receptor chimeras suggested that activation of this pathway by RXFP1 was dependent upon the membrane-anchored domain of the receptor. Further receptor mutagenesis showed that activation of the Galpha(i3)-Gbetagamma-PI3K-PKCzeta cAMP pathway by RXFP1 is dependent upon the C-terminal 10 amino acids of the receptor and absolutely requires Arg(752).
beta(1)-Adrenoceptors compensate for beta(3)-adrenoceptors in ileum from beta(3)-adrenoceptor knock-out mice.
Publisher: Wiley
Date: 2001
Cyclic AMP accumulation in rat soleus muscle: stimulation by β2- but not β3-adrenoceptors
Publisher: Elsevier BV
Date: 05-1998
DOI: 10.1016/S0014-2999(98)00021-1
Abstract: The beta-adrenoceptor subtypes involved in cyclic AMP accumulation in rat soleus muscle were studied using beta1- beta2- and beta3-adrenoceptor agonists and antagonists. Responses to (-)-isoprenaline were antagonised by (-)-propranolol (p KB = 8.32 at 0.1 microM) and by erythro-DL-1(7-methylindian-4-yloxy)-3-isopropylaminobuta n-2-ol (+/-)-ICI 118551) (pKB = 9.38 at 10 nM and 9.65 at 100 nM) but not by 2-hydroxy-5(2-((2-hydroxy-3-(4-((1-methyl-4-trifluoromethyl)1H-imidazole -2-yl)-phenoxy)propyl)amino)ethoxy)-benzamide monomethane sulfonate ((+/-)-CGP 20712A at 10 nM or 100 nM). The beta3-adrenoceptor agonist sodium-4-[-2[-2-hydroxy-2-(-3-chlorophenyl)ethylamino]propyl]phenoxya cetate (BRL 37344 at 10 pM or 10 microM) caused no significant change in basal cyclic AMP levels and had no effect on the level of cyclic AMP accumulation stimulated by (-)-isoprenaline, zinterol or forskolin. (-)-Isoprenaline pretreatment (400 microg kg(-1) h(-1), 14 days) abolished responses to (-)-isoprenaline (10 microM) and zinterol (1 microM) while BRL 37344 had no effect in either isoprenaline or vehicle-treated groups. These results show that beta3-adrenoceptor agonists do not stimulate cyclic AMP accumulation in rat soleus muscle and that (-)-isoprenaline induced increases in cyclic AMP levels are mediated predominantly by beta2-adrenoceptors. This suggests that the previously reported increase in glucose uptake by beta3-adrenoceptor agonists in skeletal muscle does not involve direct stimulation of adenylate cyclase.
Functional analysis of desensitization of the β‐adrenoceptor signalling pathway in rat cardiac tissues following chronic isoprenaline infusion
Publisher: Wiley
Date: 06-1999
Adrenoceptors and Their Second Messenger Systems
Publisher: Wiley
Date: 1993
Modulation of the Glucagon-Like Peptide-1 Receptor Signaling by Naturally Occurring and Synthetic Flavonoids
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 12-11-2010
Abstract: The glucagon-like peptide 1 receptor (GLP-1R) is a promising target for the treatment of type II diabetes mellitus because of its role in metabolic homeostasis. In recent years, difficulties with peptide therapies have driven the search for small-molecule compounds to modulate the activity of this receptor. We recently identified quercetin, a naturally occurring flavonoid, as a probe-dependent, pathway-selective allosteric modulator of GLP-1R-mediated signaling. Using Chinese hamster ovary cells expressing the human GLP-1R, we have now extended this work to identify the structural requirements of flavonoids to modify GLP-1R binding and signaling (cAMP formation and intracellular Ca(2+) mobilization) of each of the GLP-1R endogenous agonists, as well as the clinically used exogenous peptide mimetic exendin-4. This study identified a chemical series of hydroxyl flavonols with the ability to selectively augment calcium (Ca(2+)) signaling in a peptide agonist-specific manner, with effects only on truncated GLP-1 peptides [GLP-1(7-36)NH(2) and GLP-1(7-37)] and exendin-4, but not on oxyntomodulin or full-length GLP-1 peptides [GLP-1(1-36)NH(2) and GLP-1(1-37)]. In addition, the 3-hydroxyl group on the flavone backbone (i.e., a flavonol) was essential for this activity, however insufficient on its own, to produce the allosteric effects. In contrast to hydroxyl flavonols, catechin had no effect on peptide-mediated Ca(2+) signaling but negatively modulated peptide-mediated cAMP formation in a probe-dependent manner. These data represent a detailed examination of the action of different flavonoids on peptide agonists at the GLP-1R and may aid in the development of future small molecule compounds targeted at this receptor.
Atypical pharmacologies at β‐adrenoceptors
Publisher: Wiley
Date: 10-2008
DOI: 10.1038/BJP.2008.293
Regulation of β1-, β2-adrenoceptors and adenylate cyclase in guinea-pig heart after chronic (−)-isoprenaline infusion
Publisher: Elsevier BV
Date: 07-1990
β-Adrenoceptor subtypes in the kidney
Publisher: Elsevier BV
Date: 1983
Physiological or pathological — a role for relaxin in the cardiovascular system?
Publisher: Elsevier BV
Date: 04-2003
DOI: 10.1016/S1471-4892(03)00011-0
Abstract: The omnipresent 6kDa polypeptide relaxin (RLX) is emerging as a multi-functional endocrine and paracrine factor, with a broad range of target tissues that includes the cardiovascular system. Humans and other higher primates have three RLX genes, designated H1, H2 and H3, of which H2 RLX is the major stored and circulating form. Rodents have only two RLX genes: relaxin-1 (equivalent to H2 RLX) and relaxin-3 (equivalent to H3 RLX). The recent cloning of the human RLX receptor (LGR7), a member of the leucine-rich repeat family of G-protein-coupled orphan receptors, and detection of LGR7 gene transcripts in the heart confirm this organ as a target for RLX (H2). However, evidence for production of the ligand within the cardiovascular system is limited, and few studies have clearly identified the physiological effects of RLX on cardiac function. To add to the controversy, serum concentrations and expression of RLX in the heart are elevated in chronic heart failure patients and animal models of cardiomyopathy, implying that RLX may only be a marker for pathological cardiovascular conditions, rather than normal physiology.
Memory processing in the avian hippocampus involves interactions between beta-adrenoceptors, glutamate receptors, and metabolism.
Publisher: Springer Science and Business Media LLC
Date: 06-02-2008
DOI: 10.1038/NPP.2008.5
Abstract: Noradrenaline is known to modulate memory formation in the mammalian hippoc us. We have examined how noradrenaline and selective beta-adrenoceptor (AR) agonists affect memory consolidation and how antagonists inhibit memory consolidation in the avian hippoc us. Injection of selective beta-AR agonists and antagonists at specific times within 30 min of a weakly or strongly reinforced, single-trial, bead discrimination learning test in 1-day-old chicks allowed us to determine the pattern of beta-AR involvement in hippoc al memory processing. Different beta-AR subtypes were recruited in temporal sequence after learning in the order beta(1), beta(3), and beta(2.) We provide evidence that the effect of manipulation of beta(1)-ARs by selective agonists and antagonists within 2.5 min of training parallels the action of NMDA receptor agonists and antagonists. Activation of beta(3)- and beta(2)-ARs facilitated memory but utilized different mechanisms: beta(3)-ARs by stimulating glucose uptake and metabolism, and beta(2)-ARs by increasing the breakdown of glycogen--with both metabolic events occurring in astrocytes and affecting intermediate memory. The different receptors are activated at different times within the lifetime of labile memory and within 30 min of learning. We have defined separate roles for the three beta-ARs in memory and demonstrated that the avian hippoc us is involved in learning and memory in much the same way as the hippoc us in the mammalian brain.
Characterization of β1 - and β2 -adrenoceptors in rat skeletal muscles
Publisher: Elsevier BV
Date: 10-1991
DOI: 10.1016/0006-2952(91)90516-8
Abstract: Binding studies with (-)-[125I]cyanopindolol (ICYP) were conducted to characterize beta-adrenoceptors in plantaris and soleus muscles of rats (male, 250-300 g). The distribution of beta 1- and beta 2-adrenoceptors in different muscle fiber types, identified in serial sections by succinic dehydrogenase (SDH) staining, was studied by autoradiography. The densities of binding sites (Bmax, fmol/mg protein) were 5.4 +/- 0.9 (mean +/- SEM) in plantaris and 11.5 +/- 2.0 in soleus muscle. In plantaris muscle, monophasic competition curves were observed when binding experiments were performed using CGP20712A (50 pM to 0.5 mM), a beta 1-adrenoceptor selective antagonist, or ICI 118,551 (50 pM to 20 microM), a beta 2-adrenoceptor selective antagonist, to compete for ICYP binding. Analysis with LIGAND revealed a single binding site with a KD value of 2.41 +/- 0.56 nM (mean +/- SEM) for ICI 118,551 and 8.93 +/- 3.00 microM for CGP 20712A, indicating the presence of a homogeneous population of beta 2-adrenoceptors. In soleus muscle, competition curves were biphasic with 16-21% beta 1-adrenoceptors. Autoradiographic studies supported the findings from binding studies with membrane homogenates. The ICYP binding pattern was associated closely with the muscle fiber types identified by SDH staining. Propranolol-resistant binding sites were observed, and these sites were associated with muscle fibers positive to SDH staining.
The rush to adrenaline: drugs in sport acting on the β‐adrenergic system
Publisher: Wiley
Date: 06-2008
DOI: 10.1038/BJP.2008.164
Effects of monoamine oxidase inhibitors on the hypothermia produced in cats by halothane
Publisher: Wiley
Date: 10-1969
DOI: 10.1111/J.1476-5381.1969.TB10577.X
Abstract: 1. In cats, the effects of intraperitoneal injections of four monoamine oxidase (MAO) inhibitors, tranylcypromine, pheniprazine, pargyline, and nialamide, were examined on rectal temperature and on the hypothermia during anaesthesia produced by a 2 hr period of halothane inhalation.2. A 2 hr period of halothane inhalation produced a steady fall in temperature amounting to between 2 degrees and 3.5 degrees C. After discontinuation of halothane inhalation, temperature quickly returned to the pre-anaesthetic level but no pyrexia developed. A peculiar stiffness of the leg muscles occurred in several experiments either at the beginning of the inhalation or after its discontinuation.3. An injection of tranylcypromine (5 mg/kg) caused a rise in rectal temperature and prevented the hypothermia of halothane anaesthesia. This effect lasted for at least 4 hr 20 hr after the injection, halothane again caused hypothermia.4. An injection of pheniprazine (10 mg/kg) usually caused a small rise in temperature which was not sustained. Pheniprazine not only prevented the hypothermia of halothane anaesthesia during the subsequent 20 hr, but during the first few hours after the injection halothane inhalation actually produced a steep rise in temperature.5. An injection of pargyline (50 mg/kg) had no effect on temperature but the hypothermia due to halothane inhalation was prevented 1 hr after the injection and attenuated after 20 hr. Injection of 200 mg/kg caused a steady rise in temperature which was accelerated when halothane was administered 1 hr later.6. An injection of nialamide (10, 25 or 50 mg/kg) had no immediate effect on temperature, but pyrexia developed overnight after the two larger doses. The effect on the hypothermia due to halothane inhalation was greater 20 hr after the injection than it was after 1 to 2 hr. Twenty hours after injection of the two larger doses, halothane no longer produced hypothermia but caused a lethal rise in temperature either during or after its inhalation.7. In rabbits, the effect on temperature of halothane inhalation varied. Either temperature rose slightly or it fell, but not as much as in cats. In one rabbit in which the inhalation had produced a transient rise, pyrexia developed 40 min after discontinuation of halothane.
Excitatory amino acid projections to the nucleus accumbens septi in the rat: A retrograde transport study utilizing d[3H]aspartate and [3H]GABA
Publisher: Elsevier BV
Date: 08-1987
DOI: 10.1016/0306-4522(87)90345-9
Abstract: Afferents to the nucleus accumbens septi utilizing glutamate or aspartate have been investigated in the rat by autoradiography following injection and retrograde transport of D[3H]aspartate. Parallel experiments with the intra-accumbal injection of [3H]GABA were employed to establish the transmitter-selective nature of the retrograde labelling found with D[3H]aspartate. The topography of cortical and thalamic perikarya labelled by D[3H]aspartate was extremely precise. D[3H]Aspartate labelled perikarya were found in layer V of agranular insular cortex bilaterally within prelimbic and infralimbic subareas perikarya, but predominantly ipsilaterally. Ipsilateral labelling was observed in dorsal, ventral and posterior agranular insular cortices, and in perirhinal cortex. Injections into ventral accumbens labelled perikarya in ipsilateral entorhinal cortex, while infusion of D[3H]aspartate into anterior caudate-putamen resulted in labelling of perikarya in ipsilateral cingulate and lateral precentral cortices. Following infusion of D[3H]aspartate, ipsilateral midline thalamic nuclei contained the highest density of labelled perikarya infusions centred on nucleus accumbens resulted in heavy retrograde labelling of the parataenial nucleus, but labelling was sparse from a lateral site and not observed after injection into anterior caudate-putamen. Less prominent labelling of perikarya was seen in other thalamic nuclei (mediodorsal, central medial, rhomboid, reuniens and centrolateral), mostly near the midline. Perikaryal labelling was also found in the ipsilateral amygdaloid complex, particularly in basolateral and lateral nuclei. Only weak labelling resulted in ventral subiculum. Numerous labelled cells were present bilaterally in anterior olfactory nucleus, although perikarya were more prominent ipsilaterally. Labelled perikarya were not consistently observed in other regions (ventral tegmental area, medial substantia nigra, raphe nuclei and locus coeruleus) known to innervate nucleus accumbens. Presumptive anterograde labelling was detected in ventral pallidum/substantia innominata, ventral tegmental area and medial substantia nigra. [3H]GABA was generally not retrogradely transported to the same regions labelled by D[3H]aspartate an exception being the anterior olfactory nucleus, where large numbers of labelled perikarya were found. [3H]GABA failed to label perikarya in thalamus and amygdala, and a topographic distribution of label was absent in neocortex.(ABSTRACT TRUNCATED AT 400 WORDS)
Autoradiographic localization of receptors in the cardiovascular system
Publisher: Elsevier BV
Date: 07-1987
The autoradiographic localization of adenylate cyclase in rat kidney using [3H]forskolin
Publisher: Elsevier BV
Date: 03-1990
DOI: 10.1016/0006-2952(90)90280-X
Abstract: The localization of [3H]forskolin binding to microscope slide mounted sections of rat kidney has been examined using autoradiography. Saturation studies showed [3H]forskolin binding to two sites, a high affinity site (KD = 8.7 nM, Bmax = 0.14 pmol/mg protein) and a low affinity site (KD = 6.7 microM, Bmax = 11.0 pmol/mg protein). Autoradiographs showed high affinity binding (thought to identify stimulatory guanine nucleotide binding protein (Gs)-linked adenylate cyclase) to all renal structures known to possess hormone sensitive adenylate cyclase, including all tubular segments, glomeruli and blood vessels. High concentrations of binding were associated with a portion of the proximal tubule and with papillary collecting tubules and ducts.
Identification of binding sites with differing affinity and potency for relaxin analogues on LGR7 and LGR8 Receptors
Publisher: Wiley
Date: 05-2005
Abstract: This study defines the pharmacologic characteristics of LGR7 and LGR8, the receptors for H2 relaxin and INSL3 respectively, and determines the relative activity of relaxin-related peptides. We show, for the first time, the availability of two binding sites at LGR8 and confirm the presence of two sites at LGR7. Relaxin-related peptides had differing rank orders of affinity and potency at LGR7 and LGR8, but chimeric receptors were highly similar to their ectodomain-origin native receptors. The high-affinity site on the ectodomain coupled efficiently to cAMP production, whereas the low-affinity site in the transmembrane region coupled with decreased efficiency.
High throughput, quantitative analysis of human osteoclast differentiation and activity
Publisher: Elsevier BV
Date: 02-2017
Abstract: Osteoclasts are multinuclear cells that degrade bone under both physiological and pathophysiological conditions. Osteoclasts are therefore a major target of osteoporosis therapeutics aimed at preserving bone. Consequently, analytical methods for osteoclast activity are useful for the development of novel biomarkers and/or pharmacological agents for the treatment of osteoporosis. The nucleation state of an osteoclast is indicative of its maturation and activity. To date, activity is routinely measured at the population level with only approximate consideration of the nucleation state (an 'osteoclast population' is typically defined as cells with ≥3 nuclei). Using a fluorescent substrate for tartrate-resistant acid phosphatase (TRAP), a routinely used marker of osteoclast activity, we developed a multi-labelled imaging method for quantitative measurement of osteoclast TRAP activity at the single cell level. Automated image analysis enables interrogation of large osteoclast populations in a high throughput manner using open source software. Using this methodology, we investigated the effects of receptor activator of nuclear factor kappa-B ligand (RANK-L) on osteoclast maturation and activity and demonstrated that TRAP activity directly correlates with osteoclast maturity (i.e. nuclei number). This method can be applied to high throughput screening of osteoclast-targeting compounds to determine changes in maturation and activity.
The chemistry and biology of human relaxin-3
Publisher: Wiley
Date: 05-2005
Abstract: A novel member of the human relaxin subclass of the insulin superfamily was recently discovered during a genomics database search and named relaxin-3. Like human relaxin-1 and relaxin-2, relaxin-3 is predicted to consist of a two-chain structure and three disulfide bonds in a disposition identical to that of insulin. To undertake detailed biophysical and biological characterization of the peptide, its chemical synthesis was undertaken. In contrast to human relaxin-1 and relaxin-2, however, relaxin-3 could not be successfully prepared by simple combination of the in idual chains, thus necessitating recourse to the use of a regioselective disulfide bond formation strategy. Solid phase synthesis of the separate, selectively S-protected A and B chains followed by their purification and the subsequent stepwise formation of each of the three disulfides led to the successful acquisition of human relaxin-3. Comprehensive chemical characterization confirmed both the correct chain orientation and the integrity of the synthetic product. Relaxin-3 was found to bind to and activate native relaxin receptors in vitro and stimulate water drinking through central relaxin receptors in vivo. Recent studies have demonstrated that relaxin-3 will bind to and activate human LGR7, but not LGR8, in vitro. Secondary structural analysis showed it to adopt a less ordered confirmation than either relaxin-1 or relaxin-2, reflecting the presence in the former of a greater percentage of nonhelical forming amino acids. NMR spectroscopy and simulated annealing calculations were used to determine the three-dimensional structure of relaxin-3 and to identify key structural differences between the human relaxins.
AUTORADIOGRAPHIC EVIDENCE FOR A HETEROGENEOUS DISTRIBUTION OF α1‐ ADRENORECEPTORS LABELLED BY [3 H] PRAZOSIN IN RAT, DOG AND HUMAN KIDNEY
Publisher: Wiley
Date: 06-1986
DOI: 10.1111/J.1474-8673.1986.TB00637.X
Abstract: The selective alpha1-adrenoreceptor antagonist radioligand [3H] prazosin has been used to localize alpha1-adrenoreceptors in slide mounted sections of rat, dog and human kidney. The biochemical characteristics of [3H] prazosin binding to rat kidney sections were examined and found to be saturable, reversible, stereoselective, with a KD of 0.12 nM and Bmax of 6.72 +/- 0.2 fmoles/section. 3H Ultrofilm images of [3H] prazosin binding to rat, dog, and human kidney revealed binding to the vasculature but in the rat additional receptors were confined to the renal cortex. In the rat kidney autoradiography using emulsion coated coverslips showed that binding in the renal cortex was largely to proximal tubules. In all three species the autoradiographic studies support a role for alpha1-adrenoreceptors in control of renal blood flow. In the rat the location of alpha1-adrenoreceptors suggests that they can also have an important influence on fluid and electrolyte balance, gluconeogenesis and production of prostanoids.
A STUDY OF α1-ADRENOCEPTORS IN RAT RENAL CORTEX: COMPARISON OF [3H]-PRAZOSIN BINDING WITH THE α1-ADRENOCEPTOR MODULATING GLUCONEOGENESIS UNDER PHYSIOLOGICAL CONDITIONS
Publisher: Wiley
Date: 09-1982
DOI: 10.1111/J.1476-5381.1982.TB09284.X
Abstract: 1 A comparison has been made of the alpha 1-adrenoceptor controlling gluconeogenesis in tubules from rat renal cortex and [3H]-prazosin binding in membranes prepared from the same tissue under physiological conditions. 2 In renal tubules the alpha-adrenoceptor agonists, oxymetazoline, (--)-noradrenaline, (--)-alpha-methylnoradrenaline and (--)-phenylephrine, stimulated gluconeogenesis from pyruvate. Oxymetazoline was the most potent agonist (EC50 15.7 nM) but produced only 61% of the maximum response elicited by (--)-noradrenaline. 3 The alpha-adrenoceptor antagonists, BE2254, prazosin, indoramin and phentolamine inhibited (--)-noradrenaline-mediated increases in gluconeogenesis. The alpha 1-adrenoceptor selective compounds, BE2254 and prazosin, were the most effective antagonists with KB values of 0.74 and 1.47 nM respectively. 4 [3H]-prazosin binding to membranes prepared from rat renal cortex in physiological saline at 37 degrees C was best described by a two site model. High affinity, but not low affinity sites had characteristics consistent with alpha-adrenoceptors. 5 High affinity [3H]-prazosin binding could be completely displaced by the alpha-adrenoceptor agonists, oxymetazoline, (--)-noradrenaline, (--)-phenylephrine, and (--)-alpha-methylnoradrenaline. Slope factors for the displacement curves were all significantly less than unity. The concentrations of agonists required to displace [3H]-prazosin binding were markedly higher than those required to stimulate gluconeogenesis. 6 High-affinity [3H]-prazosin binding was also displaced by the alpha-adrenoceptor antagonists, prazosin, BE2254, phentolamine and indoramin. Slope factors for the displacement curves were close to unity. Ki values calculated from the binding experiments were very similar to KB values obtained in the gluconeogenesis studies. These results suggest that in rat renal cortex the alpha 1-adrenoceptor labelled by [3H]-prazosin is probably that which stimulates gluconeogenesis.
Improving type 2 diabetes through a distinct adrenergic signaling pathway involving mTORC2 that mediates glucose uptake in skeletal muscle
Publisher: American Diabetes Association
Date: 13-11-2014
DOI: 10.2337/DB13-1860
Abstract: There is an increasing worldwide epidemic of type 2 diabetes that poses major health problems. We have identified a novel physiological system that increases glucose uptake in skeletal muscle but not in white adipocytes. Activation of this system improves glucose tolerance in Goto-Kakizaki rats or mice fed a high-fat diet, which are established models for type 2 diabetes. The pathway involves activation of β2-adrenoceptors that increase cAMP levels and activate cAMP-dependent protein kinase, which phosphorylates mammalian target of rapamycin complex 2 (mTORC2) at S2481. The active mTORC2 causes translocation of GLUT4 to the plasma membrane and glucose uptake without the involvement of Akt or AS160. Stimulation of glucose uptake into skeletal muscle after activation of the sympathetic nervous system is likely to be of high physiological relevance because mTORC2 activation was observed at the cellular, tissue, and whole-animal level in rodent and human systems. This signaling pathway provides new opportunities for the treatment of type 2 diabetes.
CARDIAC BINDING OF [3H]INOSITOL 1,4,5-TRISPHOSPHATE FOLLOWING CHRONIC STIMULATION OF CYCLIC AMP SIGNALLING IN GUINEA PIGS
Publisher: Elsevier BV
Date: 02-1998
Abstract: Binding of [3H]inositol 1,4,5-trisphosphate ([3H]IP3) to guinea pig heart has been characterised, localised and the effect of the in vivo desensitisation of cardiac beta-adrenoceptorcyclic AMP signalling examined. Quantitative autoradiography showed highest levels of [3H]IP3 binding associated with coronary blood vessels and with the endothelial cells of the aorta and the mitral and tricuspid valves. Moderate levels of [3H]IP3 bound to the atrioventricular conducting system, cardiac valves and aortic smooth muscle. Lower levels of [3H]IP3 binding were detected in atrial and ventricular myocardium. Although the phosphoinositide signalling pathway does not contribute greatly to normal cardiac function, there is evidence of an increased importance in situations of compromised excitation-contraction such as occurs in cardiac failure or with, beta-adrenoceptor desensitisation. We examined whether chronic in vivo stimulation of beta-adrenoceptor-adenylate cyclase signalling affected cardiac binding of [3H]IP3. Infusion of guinea pigs with isoprenaline (400 micrograms kg-1 h-1, 7 days) tended to reduce [3H]IP3 binding in myocardium although not significantly (P > 0.05, n = 4). These data indicate that [3H]IP3 binding has a heterogeneous distribution in guinea pig heart with highest levels of binding discretely localised to endothelial cells. Desensitisation of beta-adrenoceptor-cyclic AMP signalling in heart did not lead to upregulation of [3H]IP3 binding.
International union of basic and clinical pharmacology. XCV. Recent advances in the understanding of the pharmacology and biological roles of relaxin family peptide receptors 1–4, the receptors for relaxin family peptides
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 11-03-2015
Increased Expression of the Relaxin Receptor (LGR7) in Human Endometrium during the Secretory Phase of the Menstrual Cycle
Publisher: The Endocrine Society
Date: 07-2004
Inotropic responses to human gene 2 (B29) relaxin in a rat model of myocardial infarction (MI): Effect of pertussis toxin
Publisher: Wiley
Date: 11-2002
Functional Domains of the Mouse β3-Adrenoceptor Associated with Differential G Protein Coupling
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 06-09-2005
Abstract: Alternative splicing of mouse beta3-adrenoceptor transcripts produces an additional receptor isoform (beta3b-adrenoceptor) with a C terminus comprising 17 amino acids distinct from the 13 in the known receptor (beta3a-adrenoceptor). We have shown that the beta3b-adrenoceptor couples to both Gs and Gi, whereas the beta3a-adrenoceptor couples only to Gs. To define the regions involved in this differential G protein coupling, we have compared wild-type, truncated, and mutant beta3-adrenoceptors. In Chinese hamster ovary cells expressing beta3-adrenoceptors truncated at the splicing point, cAMP accumulation with CL316243 [(R,R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino]-propyl]1,3-benzodioxole-2,2-dicarboxylate] increased by 59% following pretreatment with pertussis toxin, suggesting that the C-terminal region of the beta3a-adrenoceptor inhibits coupling to Gi. We next utilized the cell-penetrating peptide Transportan 10 (Tp10) to introduce peptides comprising the different C-terminal tail fragments into cells expressing beta3a-adrenoceptor, beta3b-adrenoceptor, and the truncated beta3-adrenoceptor. Treatment with beta3a-Tp10 (1 microM) caused cAMP responses to CL316243 in the beta3a-adrenoceptor to become pertussis toxin-sensitive and display a 30% increase over control, whereas the other peptides did not affect any receptor. Mutation at a potential tyrosine phosphorylation site (Tyr392Ala beta3a-adrenoceptor) did not alter responses or pertussis toxin sensitivity relative to the parent receptor. Surprisingly, a Ser388Ala/Ser389Ala mutant beta3b-adrenoceptor became unresponsive to CL316243 while retaining an extracellular acidification rate response to SR59230A [3-(2-ethylphenoxy)-1-[(1,S)-1,2,3,4-tetrahydronapth-1-ylamino]-2S-2-propanol oxalate]. Our findings suggest that the beta3a-adrenoceptor cannot couple to Gi because of conformational changes induced by a protein(s) that interacts with residues in the C-terminal tail or because this protein(s) affects the intracellular localization of the beta3a-adrenoceptor.
Orthosteric binding of rho-Da1a, a natural peptide of snake venom interacting selectively with the alpha(1A)-Adrenoceptor
Publisher: Public Library of Science (PLoS)
Date: 25-07-2013
The Janus faces of adrenoceptors: factors controlling the coupling of adrenoceptors to multiple signal transduction pathways.
Publisher: Wiley
Date: 11-2004
DOI: 10.1111/J.1440-1681.2004.04094.X
Abstract: 1. The adrenoceptors (AR) are an important subfamily of rhodopsin-like G-protein-coupled receptors that couple to an increasingly large number of signalling mechanisms. Two important factors that determine the pathways that are used are the C-terminal region of the receptor and the agonist used to activate the receptor. 2. Studies of splice variants of the mouse beta3-AR showed that the C-terminus is a factor controlling the signalling characteristics. Although these receptors differ only at the C-terminus, the beta3b-AR coupled to both Gs and Gi, whereas the beta3a-AR coupled solely to Gs. 3. Examination of four splice variants of the human alpha1A-AR showed that all were able to couple to pertussis toxin-sensitive G-proteins, even though they have radically different C-terminal regions. 4. Comparison of the effects of the beta3-AR ligands CL316243 and SR59230A showed that both can activate the mouse beta3-AR but that SR59230A uses pathways other than cAMP accumulation in 3T3-F442A cells. 5. Examination of a series of alpha1-AR agonists for their ability to activate a number of signalling pathways revealed that A61603 acted as a full agonist in all assays, whereas oxymetazoline was unable to cause cAMP accumulation, suggesting agonist-selective signalling at the human alpha1A-AR.
Orthosteric, Allosteric and Biased Signalling at the Relaxin-3 Receptor RXFP3
Publisher: Springer Science and Business Media LLC
Date: 21-08-2015
DOI: 10.1007/S11064-015-1701-3
Abstract: Relaxin-3 is a neuropeptide that has roles in stress, memory and appetite regulation. The peptide acts on its cognate receptor RXFP3 to induce coupling to inhibitory G proteins to inhibit adenylyl cyclase and activate MAP-kinases such as ERK1/2, p38MAPK and JNK. Other relaxin family peptides can activate the receptor to produce alternative patterns of signalling and there is an allosteric modulator 135PAM1 that displays probe-selectivity. There are now a variety of selective peptide agonists and antagonists that will assist in the determination of the physiological roles of the relaxin-RXFP3 system and its potential as a drug target.
AT1R-AT2R-RXFP1 Functional Crosstalk in Myofibroblasts
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-09-2019
Abstract: Studies have shown that the hormone serelaxin, which has organ-protective actions mediated via relaxin family peptide receptor 1 (RXFP1), its cognate G protein–coupled receptor, requires the angiotensin II type 2 receptor (AT 2 R) to ameliorate renal fibrogenesis in vitro and in vivo . In this study, the authors describe a functional interaction between RXFP1, AT 2 R, and the angiotensin II type 1 receptor (AT 1 R), all of which are expressed on extracellular matrix–producing myofibroblasts, the cellular basis of progressive fibrosis. The crosstalk between these G protein–coupled receptors allows antagonists acting at each receptor to directly or allosterically block the antifibrotic actions of agonists acting at AT 2 R or RXFP1. These findings have significant therapeutic implications for a mechanistic understanding of the concomitant use of drugs acting at each receptor. Recombinant human relaxin-2 (serelaxin), which has organ-protective actions mediated via its cognate G protein–coupled receptor relaxin family peptide receptor 1 (RXFP1), has emerged as a potential agent to treat fibrosis. Studies have shown that serelaxin requires the angiotensin II (AngII) type 2 receptor (AT 2 R) to ameliorate renal fibrogenesis in vitro and in vivo . Whether its antifibrotic actions are affected by modulation of the AngII type 1 receptor (AT 1 R), which is expressed on myofibroblasts along with RXFP1 and AT 2 R, is unknown. We examined the signal transduction mechanisms of serelaxin when applied to primary rat renal and human cardiac myofibroblasts in vitro , and in three models of renal- or cardiomyopathy-induced fibrosis in vivo . The AT 1 R blockers irbesartan and candesartan abrogated antifibrotic signal transduction of serelaxin via RXFP1 in vitro and in vivo . Candesartan also ameliorated serelaxin’s antifibrotic actions in the left ventricle of mice with cardiomyopathy, indicating that candesartan’s inhibitory effects were not confined to the kidney. We also demonstrated in a transfected cell system that serelaxin did not directly bind to AT 1 Rs but that constitutive AT 1 R–RXFP1 interactions could form. To potentially explain these findings, we also demonstrated that renal and cardiac myofibroblasts expressed all three receptors and that antagonists acting at each receptor directly or allosterically blocked the antifibrotic effects of either serelaxin or an AT 2 R agonist (compound 21). These findings have significant implications for the concomitant use of RXFP1 or AT 2 R agonists with AT 1 R blockers, and suggest that functional interactions between the three receptors on myofibroblasts may represent new targets for controlling fibrosis progression.
The simultaneous determination of 3,4-dihydroxyphenylethylene glycol, 3,4-dihydroxyphenylacetic acid and catecholamines in brain tissue by high performance liquid chromatography with electrochemical d
Publisher: Elsevier BV
Date: 08-1983
DOI: 10.1016/0304-3940(83)90390-7
Abstract: An assay is described for the simultaneous determination of the deaminated metabolites 3,4-dihydroxyphenylethylene glycol (DHPG) and 3,4-dihydroxyphenylacetic acid (DOPAC), together with noradrenaline, dopamine and adrenaline in brain using high performance liquid chromatography with electrochemical detection. The procedure is simple, specific, and has a limit of detection for each catechol of 5 pg. It offers the advantage of measuring the major monoamine oxidase metabolites of both noradrenaline (i.e. DHPG) and dopamine (i.e. DOPAC), which in some circumstances may reflect neuronal activity, simultaneously with their catecholamine neurotransmitter precursors.
The effects of amiodarone (L 3428), an α and β receptor antagonist, on overflow of transmitter and uptake of noradrenaline in the cat spleen
Publisher: Elsevier BV
Date: 12-1974
Changes in the Innervation and Catecholamine Concentrations in the Myometrium of Pregnant and Non-Pregnant Sheep
Publisher: S. Karger AG
Date: 1986
DOI: 10.1159/000146145
Abstract: The innervation of the myometrium in virgin, pregnant and post-partum ewes was examined using the SPG histofluorescence method and a high-performance liquid chromatographic catecholamine assay. In non-pregnant ewes, fluorescent axons were visible in all regions of the uterus. At 50 days of pregnancy the innervation was unchanged, but at 100 days axons were scarce over the whole uterus with the exception of the tubal extremities of the uterine horns. Noradrenaline concentrations were also significantly lower in late pregnancy, and significant variations occurred in different regions of the uterus, with the greatest concentrations present in the tubal extremities. At 13–16 weeks post partum, the density of innervation was variable, although the noradrenaline concentration was only slightly less than in virgin animals. Dopamine was also present in substantial quantities, but the mean concentrations remained unchanged during pregnancy.
Absence of mitochondrial β-adrenoceptors in guinea pig myocardium: Evidence for tissue disparity
Publisher: Elsevier BV
Date: 09-1992
DOI: 10.1016/0306-3623(92)90232-9
Abstract: 1. Binding sites in guinea pig myocardial tissue labelled by (-)-[125I] cyanopindolol (CYP) were investigated using differential centrifugation and autoradiographic techniques. Autoradiographs of myocardial sections (0.1 microns) indicated (-)-[125I]CYP binding to sarcolemmal membrane. A low density of binding sites was observed to mitochondria. 2. Binding studies were performed in subcellular fractions. The density of binding sites in the mitochondrial fraction (36.1 +/- 9.4 fmol/mg protein) was less than 10% that in the sarcolemmal membrane (371.7 +/- 38.2 fmol/mg protein). The beta 1/beta 2-adrenoceptor subtype ratio in the mitochondrial fraction (83.3/16.7) was similar to that in the sarcolemmal fraction (87.1/12.9). 3. Ouabain (100 microM), in the presence of sodium azide (0.4 mM), inhibited a Na+K+ stimulated ATPase activity (1.0 +/- 0.2 mumol Pi/mg protein/hr reduction), indicating a low but significant level of sarcolemmal contamination of the mitochondrial fraction. 4. The study showed beta-adrenoceptors in guinea pig heart are located primarily on the sarcolemmal membrane of myocardium. No evidence was obtained for beta-adrenoceptors over mitochondria, as has been suggested in other tissues and species, but that this binding was to sarcolemmal inclusions in the mitochondrial fraction.
Localization and function of components of the β-adrenergic system in human and blood vessels
Publisher: Elsevier BV
Date: 07-1990
Relaxin activates multiple cAMP signaling pathway profiles in different target cells
Publisher: Wiley
Date: 04-2009
DOI: 10.1111/J.1749-6632.2008.03814.X
Abstract: Although RXFP1-cAMP signaling in HEK293T cell systems is now relatively well-defined, the signaling pathways activated by relaxin in its target cells and tissues are still unclear. This study aimed to examine the cAMP signaling of RXFP1 in cells that endogenously express the receptor. Seven cell types derived from various backgrounds were screened for receptor expression. Only in THP-1 cells and rat cardiac fibroblasts was there activation of the Galpha(i3)-Gbetagamma-phosphatidylinositol 3-kinase-protein kinase Czeta pathway, leading to cAMP accumulation. In all other cells there was activation of a combination of the initial pathways to affect cAMP. T-47D cells could activate only Galpha(s), whereas Colo 16 and rat renal fibroblasts from obstructed kidney could activate both Galpha(s) and Galpha(oB) pathways. Thus, the signaling pathways activated by relaxin are highly dependent upon the cell type under investigation, and this may help to explain the varied physiological responses exerted by relaxin in its different target tissues.
Receptors for relaxin family peptides
Publisher: Wiley
Date: 05-2005
Abstract: Recent studies have identified four receptors that are the physiological targets for relaxin family peptides. All are class I (rhodopsin like) G-protein-coupled receptors with LGR7 (RXFP1) and LGR8 (RXFP2) being type C leucine-rich repeat-containing receptors, whereas GPCR135 (RXFP3) and GPCR142 (RXFP4) resemble receptors that respond to small peptides such as somatostatin and angiotensin II. The cognate ligands for the receptors have been identified: relaxin for RXFP1 INSL3 for RXFP2 relaxin 3 for RXFP3 and INSL5 for RXFP4. RXFP1 and RXFP2 receptors produce increases in intracellular cAMP levels upon stimulation, although the response is complex and contains a component sensitive to PI-3-kinase inhibitors. There is also evidence that RXFP1 can activate Erk1/2 and nitric oxide synthase, and relaxin has been reported to enter cells and activate glucocorticoid receptors. In contrast, RXFP3 and RXFP4 couple to Gi by a pertussis toxin-sensitive mechanism to cause inhibition of cAMP production. Now that the receptors for relaxin family peptides and their cognate ligands have been identified, we suggest a nomenclature for both the peptides and the receptors that we hope will be helpful to researchers in this rapidly advancing field.
Isoform-Specific Biased Agonism of Histamine H3Receptor Agonists
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 18-11-2016
Abstract: The human histamine H
Relaxin family peptide receptors in GtoPdb v.2023.1
Publisher: Edinburgh University Library
Date: 26-04-2023
DOI: 10.2218/GTOPDB/F60/2023.1
Abstract: Relaxin family peptide receptors (RXFP, nomenclature as agreed by the NC-IUPHAR Subcommittee on Relaxin family peptide receptors [23, 119]) may be ided into two pairs, RXFP1/2 and RXFP3/4. Endogenous agonists at these receptors are heterodimeric peptide hormones structurally related to insulin: relaxin-1, relaxin, relaxin-3 (also known as INSL7), insulin-like peptide 3 (INSL3) and INSL5. Species homologues of relaxin have distinct pharmacology and relaxin interacts with RXFP1, RXFP2 and RXFP3, whereas mouse and rat relaxin selectively bind to and activate RXFP1 [260]. relaxin-3 is the ligand for RXFP3 but it also binds to RXFP1 and RXFP4 and has differential affinity for RXFP2 between species [259]. INSL5 is the ligand for RXFP4 but is a weak antagonist of RXFP3. relaxin and INSL3 have multiple complex binding interactions with RXFP1 [267] and RXFP2 [132] which direct the N-terminal LDLa modules of the receptors together with a linker domain to act as a tethered ligand to direct receptor signaling [262]. INSL5 and relaxin-3 interact with their receptors using distinct residues in their B-chains for binding, and activation, respectively [321, 152].
Assay of brain 3,4-dihydroxyphenylethyleneglycol (DHPG) levels by high-performance liquid chromatography with electrochemical detection
Publisher: Elsevier BV
Date: 1984
DOI: 10.1016/S0021-9673(01)87682-2
Abstract: Synchronization is a fundamental characteristic of complex systems and a basic mechanism of self-organization. A traditional, accepted perspective on epileptiform activity holds that hypersynchrony covering large brain regions is a hallmark of generalized seizures. However, a few recent reports have described substantial fluctuations in synchrony before and during ictal events, thus raising questions as to the widespread synchronization notion. In this study, we used magnetoencephalographic recordings from epileptic patients with generalized seizures and normal control subjects to address the extent of the phase synchronization (phase locking) in local (neighboring) and distant cortical areas and to explore the ongoing temporal dynamics for particular ranges of frequencies at which synchrony occurs, during interictal and ictal activity. Synchronization patterns were found to differ somewhat depending on the epileptic syndrome, with primary generalized absence seizures displaying more long-range synchrony in all frequency bands studied (3-55 Hz) than generalized tonic motor seizures of secondary (symptomatic) generalized epilepsy or frontal lobe epilepsy. However, all seizures were characterized by enhanced local synchrony compared with distant synchrony. There were fluctuations in the synchrony between specific cortical areas that varied from seizure to seizure in the same patient, but in most of the seizures studied, regardless of semiology, there was a constant pattern in the dynamics of synchronization, indicating that seizures proceed by a recruitment of neighboring neuronal networks. Together, these data indicate that the concept of widespread "hypersynchronous" activity during generalized seizures may be misleading and valid only for very specific neuronal ensembles and circumstances.
Adrenoceptors in GtoPdb v.2023.1
Publisher: Edinburgh University Library
Date: 26-04-2023
Abstract: The nomenclature of the Adrenoceptors has been agreed by the NC-IUPHAR Subcommittee on Adrenoceptors [64, 194]. Adrenoceptors, α1 The three α1-adrenoceptor subtypes α1A, α1B and α1D are activated by the endogenous agonists (-)-adrenaline and (-)-noradrenaline. -(-)phenylephrine, methoxamine and cirazoline are agonists and prazosin and doxazosin antagonists considered selective for α1- relative to α2-adrenoceptors. [3H]prazosin and [125I]HEAT (BE2254) are relatively selective radioligands. S(+)-niguldipine also has high affinity for L-type Ca2+ channels. Fluorescent derivatives of prazosin (Bodipy FLprazosin- QAPB) are used to examine cellular localisation of α1-adrenoceptors. α1-Adrenoceptor agonists are used as nasal decongestants antagonists to treat symptoms of benign prostatic hyperplasia (alfuzosin, doxazosin, terazosin, tamsulosin and silodosin, with the last two compounds being α1A-adrenoceptor selective and claiming to relax bladder neck tone with less hypotension) and to a lesser extent hypertension (doxazosin, terazosin). The α1- and β2-adrenoceptor antagonist carvedilol is used to treat congestive heart failure, although the contribution of α1-adrenoceptor blockade to the therapeutic effect is unclear. Several anti-depressants and anti-psychotic drugs are α1-adrenoceptor antagonists contributing to side effects such as orthostatic hypotension. Adrenoceptors, α2 The three α2-adrenoceptor subtypes α2A, α2B and α2C are activated by (-)-adrenaline and with lower potency by (-)-noradrenaline. brimonidine and talipexole are agonists and rauwolscine and yohimbine antagonists selective for α2- relative to α1-adrenoceptors. [3H]rauwolscine, [3H]brimonidine and [3H]RX821002 are relatively selective radioligands. There are species variations in the pharmacology of the α2A-adrenoceptor. Multiple mutations of α2-adrenoceptors have been described, some associated with alterations in function. Presynaptic α2-adrenoceptors regulate many functions in the nervous system. The α2-adrenoceptor agonists clonidine, guanabenz and brimonidine affect central baroreflex control (hypotension and bradycardia), induce hypnotic effects and analgesia, and modulate seizure activity and platelet aggregation. clonidine is an anti-hypertensive (relatively little used) and counteracts opioid withdrawal. dexmedetomidine (also xylazine) is increasingly used as a sedative and analgesic in human [33] and veterinary medicine and has sympatholytic and anxiolytic properties. The α2-adrenoceptor antagonist mirtazapine is used as an anti-depressant. The α2B subtype appears to be involved in neurotransmission in the spinal cord and α2C in regulating catecholamine release from adrenal chromaffin cells. Although subtype-selective antagonists have been developed, none are used clinically and they remain experimental tools. Adrenoceptors, β The three β-adrenoceptor subtypes β1, β2 and β3 are activated by the endogenous agonists (-)-adrenaline and (-)-noradrenaline. Isoprenaline is selective for β-adrenoceptors relative to α1- and α2-adrenoceptors, while propranolol (pKi 8.2-9.2) and cyanopindolol (pKi 10.0-11.0) are relatively selective antagonists for β1- and β2- relative to β3-adrenoceptors. (-)-noradrenaline, xamoterol and (-)-Ro 363 show selectivity for β1- relative to β2-adrenoceptors. Pharmacological differences exist between human and mouse β3-adrenoceptors, and the 'rodent selective' agonists BRL 37344 and CL316243 have low efficacy at the human β3-adrenoceptor whereas CGP 12177 (low potency) and L 755507 activate human β3-adrenoceptors [88]. β3-Adrenoceptors are resistant to blockade by propranolol, but can be blocked by high concentrations of bupranolol. SR59230A has reasonably high affinity at β3-adrenoceptors, but does not discriminate between the three β- subtypes [332] whereas L-748337 is more selective. [125I]-cyanopindolol, [125I]-hydroxy benzylpindolol and [3H]-alprenolol are high affinity radioligands that label β1- and β2- adrenoceptors and β3-adrenoceptors can be labelled with higher concentrations (nM) of [125I]-cyanopindolol together with β1- and β2-adrenoceptor antagonists. Fluorescent ligands such as BODIPY-TMR-CGP12177 can be used to track β-adrenoceptors at the cellular level [8]. Somewhat selective β1-adrenoceptor agonists (denopamine, dobutamine) are used short term to treat cardiogenic shock but, chronically, reduce survival. β1-Adrenoceptor-preferring antagonists are used to treat cardiac arrhythmias (atenolol, bisoprolol, esmolol) and cardiac failure (metoprolol, nebivolol) but also in combination with other treatments to treat hypertension (atenolol, betaxolol, bisoprolol, metoprolol and nebivolol) [528]. Cardiac failure is also treated with carvedilol that blocks β1- and β2-adrenoceptors, as well as α1-adrenoceptors. Short (salbutamol, terbutaline) and long (formoterol, salmeterol) acting β2-adrenoceptor-selective agonists are powerful bronchodilators used to treat respiratory disorders. Many first generation β-adrenoceptor antagonists (propranolol) block both β1- and β2-adrenoceptors and there are no β2-adrenoceptor-selective antagonists used therapeutically. The β3-adrenoceptor agonist mirabegron is used to control overactive bladder syndrome. There is evidence to suggest that β-adrenoceptor antagonists can reduce metastasis in certain types of cancer [197].
Differential regulation of β3‐adrenoceptors in gut and adipose tissue of genetically obese (ob/ob) C57BL/6J‐mice
Publisher: Wiley
Date: 06-1998
Cat assay for the emetic action of digitalis and related glycosides (digitoxin, digoxin, lanatoside C, ouabain and calactin)
Publisher: Wiley
Date: 05-1971
DOI: 10.1111/J.1476-5381.1971.TB07094.X
Abstract: 1. A titration assay with two end points is described for comparison of the emetic and lethal potencies of digitalis-like drugs.2. A drug was infused at constant rate to a conscious, unrestrained cat, through an indwelling venous cannula. At the moment of vomiting the cat was rapidly anaesthetized and infusion continued at the same rate until the moment of cardiac arrest.3. With very slow and very fast infusions, the emetic and lethal doses tended to rise. In the range between these extremes (which varied from drug to drug) they were independent of time.4. The observations could be accounted for by analogue computation, assuming that the drugs entered an initial pool and were distributed at finite rates to receptors in the CNS (vomiting centre) and heart.5. Half times of metabolic loss derived from this computation for digitoxin, digoxin and ouabain (17, 9.9 and 1.8 h, respectively) were in the same ratio as the threefold longer half times reported for these drugs in man.6. When measured with infusion rates in the time independent range, the ratio of lethal to emetic doses did not vary between the drugs studied. All caused vomiting at 40% of the lethal dose.7. From a review of the literature, the emetic and cardiotoxic actions of digitalis-like drugs appear inseparable and probably share a common biochemical mechanism.8. It is concluded that foreseeable improvements in digitalis-like drugs are small and would depend on the elimination of any local emetic effect on gut receptors which they may have.
Quantification of functional selectivity at the human α(1A)-adrenoceptor.
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 26-10-2011
Abstract: Although G protein-coupled receptors are often categorized in terms of their primary coupling to a given type of Gα protein subunit, it is now well established that many show promiscuous coupling and activate multiple signaling pathways. Furthermore, some agonists selectively activate signaling pathways by promoting interaction between distinct receptor conformational states and particular Gα subunits or alternative signaling proteins. We have tested the capacity of agonists to stimulate Ca(2+) release, cAMP accumulation, and changes in extracellular acidification rate (ECAR) at the human α(1A)-adrenoceptor. Signaling bias factors were determined by novel application of an operational model of agonism and compared with the reference endogenous agonist norepinephrine values significantly different from 1.0 indicated an agonist that promoted receptor conformations distinct from that favored by norepinephrine. Oxymetazoline was a full agonist for ECAR and a partial agonist for Ca(2+) release (bias factor 8.2) but failed to stimulate cAMP production. Phenylephrine showed substantial bias toward ECAR versus Ca(2+) release or cAMP accumulation (bias factors 21 and 33, respectively) but did not display bias between Ca(2+) and cAMP pathways. Cirazoline and N-[5-(4,5-dihydro-1H-imidazol-2-yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl]methanesulfonamide (A61603) displayed bias toward cAMP relative to Ca(2+) release (bias factors of 7.4 and 8.6). It is noteworthy that epinephrine, a second endogenous adrenoceptor agonist, did not display bias relative to norepinephrine. Our finding that phenylephrine displayed significant signaling bias, despite being highly similar in structure to epinephrine, indicates that subtle differences in agonist-receptor interaction can affect conformational changes in cytoplasmic domains and thereby modulate the repertoire of effector proteins that are activated.
Multiple binding sites revealed by interaction of relaxin family peptides with native and chimeric relaxin family peptide receptors 1 and 2 (LGR7 and LGR8)
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 12-01-2005
Abstract: Relaxin family peptide 1 (RXFP1) receptor (LGR7) and RXFP2 receptor (LGR8) were recently identified as the receptor targets for H2 relaxin and insulin-like peptide 3 (INSL3), respectively. In this study, we define the pharmacology of these two receptors by using a number of receptor chimeras and relaxin family peptides. We have identified two binding sites on these receptors: one primary, high-affinity site within the ectodomain and a secondary, lower affinity site within the transmembrane region. The primary site was found to dictate receptor binding characteristics, although the lower affinity site also exerts some influence and modulates ligand affinity for the primary site in a manner dependent upon the peptide in question. Not all relaxin peptides were able to bind to the RXFP2 receptor, indicating that the relaxin-RXFP2 receptor interaction is species-specific. INSL3 was found to exhibit characteristics of a partial agonist at the RXFP2 and chimeric RXFP1/2 receptors, with low maximal cAMP responses but high potency in coupling to this pathway. cAMP accumulation studies also revealed that the binding sites couple to cAMP signaling pathways with differing efficiency: the high-affinity site signals with high efficiency, whereas the lower affinity site signals with little to no efficiency. Comparisons between RXFP1, RXFP2, the chimeric receptors, and the truncated receptors revealed that the interaction between receptor sites is critical for optimal ligand binding and signal transduction and that the ectodomain is essential for signaling. Evidence obtained in this study supports a two-stage binding model of receptor activation: binding to the primary site allows a conformational change and interaction with the low-affinity transmembrane site.
Relaxin: more than just a hormone of pregnancy
Publisher: Elsevier BV
Date: 1993
Relaxin receptors - New drug targets for multiple disease states
Publisher: Bentham Science Publishers Ltd.
Date: 2007
DOI: 10.2174/138945007779315650
Abstract: Relaxin was discovered more than 75 years prior to the identification of the receptors that mediate its actions. There has been a slow emergence in understanding the role of relaxin, with it being denoted initially as a hormone of pregnancy due to its observed effects to relax pubic ligaments and soften the cervix of guinea pigs to facilitate parturition. However, many other physiological roles have been identified for relaxin, including cardiovascular and neuropeptide functions and an ability to induce the matrix metalloproteinases, so it is clear that relaxin is not exclusively a hormone of pregnancy but has a much wider role in vivo. The recent de-orphanisation of four receptors LGR7, LGR8, GPCR135 (SALPR) and GPCR142 (GPR100) that respond to and bind at least one of the three forms of relaxin identified to date, allows dissection of this system to determine the precise role of each receptor and enable the identification of new targets for treatment of numerous disease states. Relaxin has the potential to be useful for the treatment of scleroderma, fibrosis, in orthodontics and to facilitate embryo implantation in humans. Relaxin antagonists may act as contraceptives or prevent the development of breast cancer metastases. Recent research has added considerable knowledge to the signalling pathways activated by relaxin, which will aid our understanding of how relaxin produces its effects. The focus of this review is to bring together recent developments in the relaxin receptor field and to highlight their potential as drug targets.
Localisation of [3H]clonidine binding to membranes from guinea pig renal tubules
Publisher: Elsevier BV
Date: 02-1982
DOI: 10.1016/0006-2952(82)90163-0
Abstract: The selective radioligand [3H]clonidine has been used to localise alhpa 2 adrenoceptors in guinea pig kidney. Chemical sympathectomy with 6-hydroxydopamine produced no significant change in the number of sites labeled by [3H]clonidine indicating that the majority of binding sites were not located on sympathetic nerve terminals. Binding was enhanced in membranes prepared from renal tubules and considerably reduced in preparations from glomeruli. Subcellular fractions of renal cortex revealed that binding was to plasma membranes and that the greatest binding capacity was present in the fraction rich in basal lateral membranes. It is concluded that the major concentration of renal alpha 2 adrenoceptors are present on renal tubules and that they may be localised to a particular pole of the renal tubule cell.
Cardiovascular effects of relaxin: From basic science to clinical therapy
Publisher: Springer Science and Business Media LLC
Date: 24-11-2010
DOI: 10.1038/NRCARDIO.2009.198
Abstract: Although substantial advances have been achieved in recent decades in the clinical management of heart diseases, new therapies that provide better or additional efficacy with minimal adverse effects are urgently required. Evidence that has accumulated since the 1990s indicates that the peptide hormone relaxin has multiple beneficial actions in the cardiovascular system under pathological conditions and, therefore, holds promise as a novel therapeutic intervention. Clinical trials for heart failure therapy using relaxin revealed several beneficial actions. Here we review findings from mechanistic and applied research in this field, comment on the outcomes of recent phase I/II clinical trails on patients with heart failure, and highlight settings of cardiovascular diseases where relaxin might be effective.
Response to Comment on Sato et al. Improving type 2 diabetes through a distinct adrenergic signaling pathway involving mTORC2 that mediates glucose uptake in skeletal muscle. Diabetes 2014;63:4115-4129.
Publisher: American Diabetes Association
Date: 13-11-2014
DOI: 10.2337/DB14-1283
Effects of prolonged infusion of dopexamine on β1‐ and β2‐adrenoceptors in guinea‐pig myocardium
Publisher: Wiley
Date: 06-1990
DOI: 10.1111/J.1474-8673.1990.TB00012.X
Abstract: 1. The effects of 7-day infusion of dopexamine (50 and 200 micrograms kg-1h-1) were examined on beta 1- and beta 2-adrenoceptors in guinea-pig left ventricular membranes. 2. Receptor binding performed using the high affinity radioligand (-)-[125I]-cyanopindolol (CYP) and the beta 1-adrenoceptor antagonist CGP 20712A showed that treatment with dopexamine 200 micrograms kg-1h-1 caused a 45% reduction in beta 2-adrenoceptors and a small but not significant increase in beta 1-adrenoceptors. 3. Functional effects of dopexamine were examined in the guinea-pig isolated electrically driven left atria and K(+)-depolarized uterus. Dopexamine was an antagonist at beta 1-adrenoceptors in left atria (pKB = 4.49), and a partial agonist at beta 2-adrenoceptors in the uterus (alpha = 0.78, pD2 = 6.59). 4. The effects of dopexamine on beta 1- and beta 2-adrenoceptor density in guinea-pig ventricular myocardial membranes may be related to agonist activity at beta 2-adrenoceptors and antagonist activity at beta 1-adrenoceptors.
Increased Expression of the Relaxin Receptor (LGR7) in Human Endometrium during the Secretory Phase of the Menstrual Cycle
Publisher: Wiley
Date: 05-2005
Abstract: This study investigated localization and expression of relaxin and its receptor, LGR7, in the human endometrium during the proliferative and secretory phases of the menstrual cycle. H2 relaxin binding was identified in endometrium, but not myometrium, and particularly in the epithelium of the endometrial glands and uterine lumen. Binding sites increased in the early secretory phase of the menstrual cycle and were paralleled by similar increases in LGR7 mRNA measured by Q-PCR. The increase in LGR7 expression and H2 relaxin binding in the secretory phase of the menstrual cycle suggests a specific role for relaxin after ovulation in the human uterus.
Human relaxin gene 3 (H3) and the equivalent mouse relaxin (M3) gene: Novel members of the relaxin peptide family
Publisher: Elsevier BV
Date: 2002
Relaxin-1–deficient mice develop an age-related progression of renal fibrosis
Publisher: Elsevier BV
Date: 06-2004
The characteristics of low and high affinity [3H]-prazosin binding to membranes from rat renal cortex
Publisher: Elsevier BV
Date: 02-1986
DOI: 10.1016/0006-2952(86)90228-5
Abstract: The characteristics of [3H]-prazosin binding in renal cortical membranes of the rat have been assessed under a variety of buffer conditions. At 37 degrees, in Krebs' phosphate and Tris buffer, [3H]-prazosin bound to two sites, a small population of high affinity sites with properties of alpha1-adrenoceptors and a much larger population of low affinity sites with different characteristics. High affinity [3H]-prazosin binding was insensitive to Na+, K+, Ca2+ and Mg2+ ions, but low affinity [3H]-prazosin binding was markedly increased in Krebs' phosphate or sodium phosphate buffer and further enhanced in membranes pretreated with EGTA. Binding was decreased in the presence of Ca2+, the decrease in binding mainly being due to a decrease in the number of low affinity sites labelled by the ligand. Low affinity [3H]-prazosin binding was increased at 37 degrees and relatively insensitive to alpha-adrenoceptor antagonists which were weak competitors while catecholamines failed to compete for low affinity binding. Scatchard plots of [3H]-prazosin binding performed using (-)-noradrenaline (1 mM) to define non-specific binding defined binding only to alpha 1-adrenoceptors. This provides a means of differentiating high and low affinity [3H]-prazosin binding.
The relaxin gene-knockout mouse: A model of progressive fibrosis
Publisher: Wiley
Date: 05-2005
Abstract: Relaxin is well known for its actions on collagen remodeling. To improve our understanding of the physiologic role(s) of relaxin, the relaxin gene-knockout (RLX-KO) mouse was established by our group and subsequently phenotyped. Pregnant RLX-KO mice underwent inadequate development of the pubic symphysis as well as the mammary glands and nipples compared to wild-type mice, thus preventing lactation. Later studies showed that these deficiencies were associated with increased collagen, primarily in the nipple and vagina. Analysis of male RLX-KO mice also demonstrated inadequate reproductive tract development. The testis, epididymis, and prostate of RLX-KO mice showed delayed tissue maturation and growth associated with increased collagen deposition. In nonreproductive tissues, an age-related increase in interstitial collagen (fibrosis) was also detected in the lung, heart, and kidneys of RLX-KO mice and was associated with organ dysfunction. From 6-9 months of age and onwards, all organs of RLX-KO mice, particularly male mice, underwent progressive increases in tissue weight and collagen content (all P < .05) compared with wild-type animals. The increased fibrosis contributed to bronchiole epithelium thickening and alveolar congestion (lung), atrial hypertrophy and increased ventricular chamber stiffness (heart) in addition to glomerulosclerosis (kidney). Treatment of RLX-KO mice with recombinant human relaxin in early and developed stages of fibrosis caused the reversal of collagen deposition in the lung, heart, and kidneys. Together, these findings suggest that relaxin is a naturally occurring inhibitor of collagen deposition during normal development, aging, and pregnancy and can be used to prevent the progression of fibrosis.
Magnetic Resonance Imaging Is More Sensitive Than PET for Detecting Treatment-Induced Cell Death–Dependent Changes in Glycolysis
Publisher: American Association for Cancer Research (AACR)
Date: 15-07-2019
DOI: 10.1158/0008-5472.CAN-19-0182
Abstract: These findings demonstrate superior sensitivity of MRI measurement of hyperpolarized [1-13C]pyruvate metabolism versus PET measurement of 18F-FDG uptake for detecting early changes in glycolysis following treatment-induced tumor cell death.
Characterization of β‐adrenoceptor mediated smooth muscle relaxation and the detection of mRNA for β1‐, β2‐ and β3‐adrenoceptors in rat ile
Publisher: Wiley
Date: 06-1999
An autoradiographic study of muscarinic cholinoceptors in blood vessels: no localization on vascular endothelium
Publisher: Elsevier BV
Date: 08-1988
DOI: 10.1016/0014-2999(88)90615-2
Abstract: In vitro labelling and autoradiographic techniques were used to examine the localization of [3H]quinuclidinyl benzilate ([3H]QNB) and [125I]4-iodo-QNB ([125I]4IQNB) to slide-mounted sections of rabbit aorta and pulmonary artery, cat aorta, pulmonary and superior mesenteric arteries. These vessels all respond to acetylcholine (ACh) with endothelium-dependent relaxation, yet there was no evidence for endothelium-related binding of either [3H]QNB or [125I]4IQNB. Muscarinic receptors were localized over the medial smooth muscle and, in the rabbit pulmonary artery, the density of binding increased towards the adventitia. Binding of either radioligand to sections of rabbit pulmonary artery was not affected by the muscarinic M1 receptor antagonist pirenzepine (20 nM) but was markedly reduced by the muscarinic M2 antagonist 4DAMP (4-diphenylacetoxy-N-methyl-piperidine methobromide) (1 nM). This study provides evidence for muscarinic receptors located directly on smooth muscle cells, indicating that endothelium-dependent relaxation to ACh results from an indirect mechanism involving smooth muscle muscarinic receptors.
Relaxin family peptide receptors RXFP1 and RXFP2 modulate cAMP signaling by distinct mechanisms
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 28-03-2006
Abstract: Two orphan leucine-rich repeat-containing G protein-coupled receptors were recently identified as targets for the relaxin family peptides relaxin and insulin-like peptide (INSL) 3. Human gene 2 relaxin is the cognate ligand for relaxin family peptide receptor (RXFP) 1, whereas INSL3 is the ligand for RXFP2. Constitutively active mutants of both receptors when expressed in human embryonic kidney (HEK) 293T cells signal through Galphas to increase cAMP. However, recent studies using cells that endogenously express the receptors revealed greater complexity: cAMP accumulation after activation of RXFP1 involves a time-dependent biphasic pathway with a delayed phase involving phosphoinositide 3-kinase (PI3K) and protein kinase C (PKC) zeta, whereas the RXFP2 response involves inhibition of adenylate cyclase via pertussis toxin-sensitive G proteins. The aim of this study was to compare and contrast the cAMP signaling pathways used by these two related receptors. In HEK293T cells stably transfected with RXFP1, preliminary studies confirmed the biphasic cAMP response, with an initial Galphas component and a delayed response involving PI3K and PKCzeta. This delayed pathway was dependent upon G-betagamma subunits derived from Galphai3. An additional inhibitory pathway involving GalphaoB affecting cAMP accumulation was also identified. In HEK293T cells stably transfected with RXFP2, the cAMP response involved Galphas and was modulated by inhibition mediated by GalphaoB and release of inhibitory G-betagamma subunits. Thus, initially both RXFP1 and RXFP2 couple to Galphas and an inhibitory GalphaoB pathway. Differences in cAMP accumulation stem from the ability of RXFP1 to recruit coupling to Galphai3, release G-betagamma subunits and thus activate a delayed PI3K-PKCzeta pathway to further increase cAMP accumulation.
Differential regulation of β1- and β2-adrenoceptors in guinea-pig atrioventricular conducting system after chronic (−)-isoprenaline infusion
Publisher: Elsevier BV
Date: 07-1990
The characteristics of adrenoceptors in homogenates of human cerebral cortex labelled by (3H)-rauwolscine
Publisher: Elsevier BV
Date: 09-1983
DOI: 10.1016/0024-3205(83)90667-7
Abstract: The alpha-2-adrenoceptor antagonist (3H)-rauwolscine has been used to label adrenoceptors in membranes from human cerebral cortex. The radioligand binds with high affinity (KD 2.08 nM) to a single population of sites with a density of 135 fmoles/mg protein. Adrenoceptor antagonists displaced binding in a simple monomolecular fashion with an order of affinity rauwolscine greater than yohimbine greater than phentolamine greater than corynanthine greater than prazosin indicating binding to alpha-2-adrenoceptors. Agonists displaced with an order of affinity clonidine greater than (-) adrenaline greater than (-) noradrenaline greater than dopamine greater than (-) isoprenaline but all displayed apparent Hill coefficients less than unity indicating heterogeneity of binding. The relatively high affinity of the alpha-1 antagonist prazosin for (3H)-rauwolscine binding sites in rat cerebral cortex was not observed in the human tissue which had pharmacological properties similar to those described previously in human platelet.
Autoradiographic localization of adrenoceptors in peripheral tissues
Publisher: Elsevier BV
Date: 1984
A single-chain derivative of the relaxin hormone is a functionally selective agonist of the G protein-coupled receptor, RXFP1.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5SC04754D
Abstract: A single-chain derivative of the relaxin hormone ameliorates fibrosis without side-effects.
The effects of pargyline on overflow of transmitter and uptake of noradrenaline in the cat spleen
Publisher: Wiley
Date: 04-1973
DOI: 10.1111/J.1476-5381.1973.TB08199.X
Abstract: 1. Twenty minutes after the addition of pargyline (5 x 10(-4)M) to blood perfusing the isolated spleen of the cat, the overflow of transmitter resulting from stimulation of the sympathetic nerves increased 2.3-3-fold. Lower doses of pargyline did not significantly affect overflow.2. Monoamine oxidase activity, measured with either radioactively labelled tyramine or noradrenaline as substrate, was almost completely inhibited by doses of pargyline in the range of 10(-4)M to 5 x 10(-4)M. Inhibition of enzyme activity was not correlated with the effect on overflow. Pargyline had only a slight inhibitory effect on catechol-O-methyl transferase.3. Uptake of a 1 mug injection (pulse) of labelled noradrenaline, following pargyline (5 x 10(-4)M), was increased to 199.1% of that found in control experiments.4. Pargyline significantly reduced the vascular responses to nerve stimulation but had no significant effect on capsular responses.5. The inhibitor had no effect on resting overflow of labelled noradrenaline from the spleen but doubled the overflow of labelled noradrenaline following nerve stimulation.6. It is suggested that the effect of pargyline on overflow is due to increased release of transmitter during nerve stimulation.7. The possible clinical significance of these findings is discussed.
Contrasting roles for β1, β2 and β3-adrenoceptors in memory formation in the chick
Publisher: Elsevier BV
Date: 2005
DOI: 10.1016/J.NEUROSCIENCE.2004.10.036
Abstract: Noradrenaline plays distinct roles in the modulation and consolidation of memory for one-trial, discriminated, avoidance learning in the chick. We have previously shown that activation of beta2-, beta3- and alpha1-adrenoceptors (ARs) by injection into the multimodal forebrain association region (intermediate medial hyperstriatum ventrale [IMHV] or intermediate medial mesopallium [IMM]) is involved in the consolidation of memory 30 min after training and that activation of alpha2-ARs in the caudate putamen plays a role in the reinforcement of memory leading to consolidation in the IMM (IMHV). In this paper we provide evidence that noradrenaline acts at beta1-ARs in the basal ganglia (lobus parolfactorius or medial striatum) in short-term memory processing immediately post-training and demonstrate inhibition of memory by selective AR antagonists at particular times in the sequential memory processing sequence after training. These results support separate roles for beta2- and beta3-ARs in memory consolidation. Our studies suggest that, as a consequence of the learning experience, noradrenaline acts in different brain regions and at different times in memory processing, to enhance memory through distinct populations of ARs.
SIMUL: an accurate method for the determination of receptor subtype proportions using a personal computer
Publisher: Elsevier BV
Date: 06-1990
DOI: 10.1016/0169-2607(90)90093-O
Abstract: Many tissues possess two classes of binding sites for a drug. To estimate the proportions of each it is necessary either to use selective ligands or to perform competition experiments in which the binding of a radioligand is inhibited by a selective unlabeled ligand. However, this method will only be accurate provided the radioligand is non-selective. A selectivity of 2- to 3-fold for one receptor may produce errors of 50% or more in the estimates, depending on the concentration of radioligand chosen. Since most ligands are selective to some extent simple estimates will often provide inaccurate information. The computer program described here (SIMUL) determines the proportions of receptor subtypes by considering the relative affinities of the competing agent for the receptor subtypes, the selectivity of the radioligand and their associated concentrations.
Evidence from binding studies for α2-adrenoceptors directly associated with glomeruli from rat kidney
Publisher: Elsevier BV
Date: 06-1983
DOI: 10.1016/0014-2999(83)90554-X
Abstract: Binding of the alpha 2-adrenoceptor radioligands [3H]clonidine and [3H]rauwolscine but not the alpha 1-adrenoceptor radioligand [3H]prazosin was enhanced in membranes prepared from rat isolated renal glomeruli. [3H]Rauwolscine binding to glomeruli was stereoselective with respect to the (-)-isomer of noradrenaline and the order of potency of a series of antagonists for displacement of binding indicated that the alpha 2-adrenoceptors in this preparation differ somewhat from those in some other species and tissues. Chemical sympathectomy produced no significant change in the number of sites labelled by [3H]rauwolscine indicating that few of the alpha 2-adrenoceptors in glomerular membranes are associated with sympathetic nerve terminals.
Biochemical characterization of an autoradiographic method for studying excitatory amino acid receptors using l-[3H]glutamate
Publisher: Elsevier BV
Date: 02-1989
DOI: 10.1016/0003-2697(89)90030-4
Abstract: A method was developed for radiolabeling excitatory amino acid receptors of rat brain with L-[3H]glutamate. Effective labeling of glutamate receptors in slide-mounted 10-microns sections was obtained using a low incubation volume (0.15 ml) and rapid washing: a procedure where high ligand concentrations were achieved with minimal waste. Saturation experiments using [3H]glutamate revealed a single binding site of micromolar affinity. The Bmax was trebled in the presence of Ca2+ (2.5 mM) and Cl- (20 mM) with no change in the Kd. Binding was rapid, saturable, stereospecific, and sensitive to glutamate receptor agonists. The proportions of [3H]glutamate binding sensitive to N-methyl-D-aspartate (NMDA), kainate, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) were 34, 54, and 51%, respectively. NMDA inhibited binding at a distinct subset of L-[3H]glutamate sites, whereas AMPA and kainate competed for some common sites. Labeling of sections with L-[3H]glutamate in the presence of the selective agonists allowed autoradiographic visualization of glutamate receptor subtypes in brain tissue.
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University Of Cambridge
Location: United Kingdom of Great Britain and Northern Ireland
School Of Pharmacy, University Of London
Location: United Kingdom of Great Britain and Northern Ireland
National Institute For Medical Research
Location: United Kingdom of Great Britain and Northern Ireland
Related Funding Activities
Linkage Projects - Grant ID: LP0560620
Start Date: 10-2005
End Date: 12-2007
Amount: $375,000.00
Funder: Australian Research Council
View Funded ActivityLinkage - International - Grant ID: LX0989791
Start Date: 04-2009
End Date: 03-2010
Amount: $86,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP110100288
Start Date: 2011
End Date: 12-2014
Amount: $310,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP0211545
Start Date: 2002
End Date: 12-2005
Amount: $405,279.00
Funder: Australian Research Council
View Funded Activity