Chronic effects of 6-hydroxydopamine and reserpine on myocardial adenylate cyclase

The effects of chronic administration of 6-hydroxydopamine or reserpine on catecholamine-sensitive adenylate cyclase from rat hearts were studied. Not only basal adenylate cyclase activity, but stimulation of the enzyme by norepinephrine, isoproterenol, NaF, guanylyl-imidodiphosphate, or combination of isoproterenol and guanylyl-imidodiphosphate, was significantly increased in the treated than in the control hearts. It is inferred that supersensitivity of myocardial adenylate cyclase following chronic treatment with reserpine or 6-hydroxydopamine may result from an increase in the catalytic activity of the enzyme.