THE HUMAN-HEART BETA-ADRENERGIC RECEPTORS .2. COUPLING OF BETA2-ADRENERGIC RECEPTORS WITH THE ADENYLATE-CYCLASE SYSTEM

  • 1 January 1983
    • journal article
    • research article
    • Vol. 24  (2) , 174-182
Abstract
The .beta.-adrenergic stimulation of adenylate cyclase in membranes from human auricles, ventricles and fetal heart was compared with the binding properties of .beta.-adrenergic receptors in human auricles. In terms of adenylate cyclase activation, 3 full agonists (isoproterenol, epinephrine and norepinephrine), 4 partial agonists (procaterol, salbutamol, fenoterol and zinterol), and 4 antagonists (propranolol, metoprolol, atenolol and practolol) were tested. The .beta.-adrenergic activation of adenylate cyclase in membranes from rat heart (with a majority of .beta.-adrenergic receptors), rat erythrocytes, and rat reticulocytes (with a homogeneous population of .beta.2-adrenergic receptors) served as reference. The reactivity of human heart adenylate cyclase, estimated by the Kact [activation constant] or Ki [inhibition constant] values of 11 .beta.-adrenergic agents, indicated that the activation of this enzyme occurred through receptors of the .beta.2-subtype only. Receptors of the .beta.1-subtype (50% of the total population) were not coupled to the enzyme.