THE HUMAN-HEART BETA-ADRENERGIC RECEPTORS .1. HETEROGENEITY OF THE BINDING-SITES - PRESENCE OF 50-PERCENT BETA1-ANDRENERGIC AND 50-PERCENT BETA2-ADRENERGIC RECEPTORS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 24  (2) , 169-173
Abstract
.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 [maximum binding] values; and inhibition of binding in the presence of 10 .mu.M GTP and of increasing concentrations of 4 nonselective agonists giving a Hill coefficient of 1 (isoproterenol, salbutamol, fenoterol and epinephrine), of 2 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 3 .beta.-selective antagonists (practolol, metoprolol and atenolol) and 2 .beta.-selective agonists (procaterol and zinterol). Kd values for all drugs were compatible with the coexistence in membranes from human auricles of .beta.- and .beta.2-adrenergic receptors, the relative proportions of receptors of each subclass being approximately the same.