title: Catecholamine-induced subsensitivity of adenylate cyclase associated with loss of beta-adrenergic receptor binding sites.
abstract: Injection of frogs with beta-adrenergic catecholamines for 1-24 hr produces marked subsensitivity of the erythrocyte membrane adenylate cyclase [ATP pyrophosphate-lyase (cyclizing); EC 4.6.1.1.] to in vitro stimulation by isoproterenol. The subsensitization is specific for catecholamine stimulation, since basal and fluoride-stimulated enzyme activity are unaffected. Maximum isoproterenol-stimulated adenylate cyclase activity declines by 75% in the isoproterenol-treated animals (P less than 0.001). The concentration of isoproterenol causing one-half maximal activation of adenylate cyclase, however, is unaltered. (-)[3H]Alprenolol, a potent competitive beta-adrenergic antagonist, was used to study directly the beta-adrenergic receptor binding sites in the erythrocyte membranes from control and subsensitized animals. A highly significant (P less than 0.005) 60% fall in the number of the beta-adrenergic receptor binding sites ("specific"(-)[3H]alprenolol binding sites) in the treated animals was found. The binding affinity of the sites was not markedly altered. These data suggest that beta-adrenergic catecholamines are able to regulate catecholamine sensitivity of tissues in vivo, by regulating the properties of the beta-adrenergic receptor binding sites.
mesh_terms: D000262:Adenylyl Cyclases / Q000097:blood*; D000526:Alprenolol / Q000494:pharmacology*; D000818:Animals; D001001:Anura; D001665:Binding Sites; D002395:Catecholamines / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000201:enzymology*; D005459:Fluorides / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D009638:Norepinephrine / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011941:Receptors, Adrenergic; D013237:Stereoisomerism
chemical_list: D002395:Catecholamines; D011941:Receptors, Adrenergic; D010643:Phenoxybenzamine; D000526:Alprenolol; D011433:Propranolol; D000262:Adenylyl Cyclases; D007545:Isoproterenol; D005459:Fluorides; D009638:Norepinephrine; D004837:Epinephrine; D010646:Phentolamine