dihydroergotoxine and Cardiomegaly

We have investigated alterations in adrenergic receptors and adenylate cyclase activity in cardiac membranes from rats injected with 40 mg/kg intraperitoneal isoproterenol. Reduction in the number of beta-adrenergic and alpha-adrenergic receptors, as assessed by changes in specific binding of 3H-dihydroalprenolol (DHA) and 3H-dihydroergocryptine (DHE), was observed only at 9 and 24 hours after isoproterenol injection, respectively. On the other hand, epinephrine-stimulated, NaF-stimulated, and Gpp (NH)p-stimulated adenylate cyclase activity was decreased as early as 3 hours after isoproterenol treatment without changes in the basal adenylate cyclase activity. These results demonstrate a defect in the adrenergic receptor-adenylate cyclase system during the development of catecholamine-induced cardiomyopathy and may partly explain the attenuated inotropic adrenergic response of the heart under stressful situations.

Topics: Adenylyl Cyclases; Animals; Cardiomegaly; Dihydroalprenolol; Dihydroergotoxine; Epinephrine; Isoproterenol; Male; Myocardium; Rats; Rats, Inbred Strains; Receptors, Adrenergic; Sodium Fluoride

Topics: Animals; Binding Sites; Blood Pressure; Cardiomegaly; Cardiovascular System; Dihydroergotoxine; Hypertension; Hypertension, Renal; Kidney; Lung; Membranes; Rats; Receptors, Adrenergic; Receptors, Adrenergic, alpha; Receptors, Adrenergic, beta