The human heart beta-adrenergic receptors. I. Heterogeneity of the binding sites: presence of 50% beta 1- and 50% beta 2-adrenergic receptors.
Beta-adrenergic receptors were characterized in a particulate fraction of human auricles obtained from patients operated upon for coronary insufficiency or valvular disease. [125I] Hydroxybenzylpindolol binding was evaluated in terms of kinetics; KD and Bmax values; and inhibition of binding in the presence of 10 microM GTP and of increasing concentrations of four nonselective agonists giving a Hill coefficient of 1 (isoproterenol, salbutamol, fenoterol, and epinephrine), of two nonselective antagonists giving a Hill coefficient of 1 (pindolol and propranolol), and of a series of selective drugs giving a Hill coefficient of 0.60-0.72 that included three beta 1-selective antagonists (practolol, metoprolol, and atenolol) and two beta 2- selective agonists (procaterol and zinterol). KD values for all drugs were compatible with the coexistence in membranes from human auricles of beta 1- and beta 2-adrenergic receptors, the relative proportions of receptors of each subclass being approximately the same.
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D055598:Chemical Phenomena; D002621:Chemistry; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011941:Receptors, Adrenergic / Q000302:isolation & purification*; D011943:Receptors, Adrenergic, beta / Q000145:classification / Q000302:isolation & purification*
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; C011878:iodohydroxybenzylpindolol; D010869:Pindolol