A beta-2-adrenergic receptor activates adenylate cyclase in human erythrocyte membranes at physiological calcium plasma concentrations

More information is needed about the subtype of the beta-adrenergic recepto r coupled to the G-protein-adenylate cyclase (AC) system in human erythrocy tes and about the optimal experimental conditions to study this system. In this study we describe the characteristics of spontaneous and beta-agonist- activated AC in human, erythrocytes. Human erythrocyte membranes were isola ted and AC activity was, utilized to assess the quantity, of cAMP. Our data show that the subtype beta-2 is the functional beta-adrenergic receptor in volved in such activation this modifies the beta-adrenergic-stimulated acti vity of AC in human erythrocytes, Isoproterenol in a medium with calcium (1 -10 mM, range that includes physiological plasma concentrations) enhances t he activation of AC; this effect was blocked by propranolol, but not by ate nolol, We conclude that in human erythrocytes subtype beta-2 is the functio nal beta-adrenergic receptor and that such a response depends to a large ex tent on Ca2+ concentrations. (C) 2000 Academic Press.