Adenylate cyclase activity in rat myocardium following chronic infusions of angiotensin II and epinephrine.

Adrenergic receptor response coupling pathways have been shown to differ in hypertrophied hearts in different models of hypertension. To mimic this, chronic subcutaneous infusions of epinephrine (80 nmol/h for up to 13 days) and angiotensin II (AII) (4.3 nmol/h for up to 4 weeks) were given. Myocardial-, basal-, and isoproterenol-, glucagon-, forskolin-, and Gpp(NH)p-stimulated adenylate cyclase were measured. No changes in enzyme activity were seen following AII infusion, even though myocardial hypertrophy was significant. After epinephrine infusion for 6 days, there was a decrease in isoproterenol stimulated enzyme. After 13 days of infusion, cyclase activity, both basal and stimulated, was reduced. We conclude that in hearts from different models of experimental hypertension associated with cardiac hypertrophy, there are different biochemical alterations in the beta-adrenergic receptor response coupling mechanism.