title: Cardiac adrenoceptors at low temperature: what is the experimental evidence for the adrenoceptor interconversion hypothesis?
abstract: Isolated heart preparations of frog and rat were used to test the validity of the adrenoceptor interconversion hypothesis. This hypothesis claims that low temperature converts the inotropic beta-adrenoceptors in isolated frog and rat heart to alpha-adrenoceptors. The present results do not support the adrenoceptor interconversion hypothesis. In the isolated frog ventricle, lowering the temperature from 24 C to 14 C did not significantly alter the inotropic potency of the sympathomimetic drugs isoprenaline, epinephrine, and phenylephrine and did not reduce the potency of the beta-adrenoceptor blocking drug propranolol as an epinephrine antagonist. In the isolated rat left atrium, lowering the temperature from 31 C to 17-19 C did not significantly change the inotropic potency of isoprenaline, norepinephrine and phenylephrine, did not diminish the potency of propranolol, and did not increase the potency of the alpha-adrenoceptor blocking drug phentolamine.--Benfey, B. G. Cardiac adrenoceptors at low temperature; what is the experimental evidence for the adrenoceptor interconversion hypothesis?
mesh_terms: D000818:Animals; D001001:Anura; D001667:Binding, Competitive; D004837:Epinephrine / Q000378:metabolism; D006325:Heart Atria / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013045:Species Specificity; D013696:Temperature
chemical_list: D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D007545:Isoproterenol; D009638:Norepinephrine; D004837:Epinephrine