Effect of adrenergic stimulation on adenylate cyclase activity in rat prostate

Adrenergic stimulation of the cyclic AMP system of the prostate gland of the rat has been investigated. The observed order of potency for adrenergic agonists in stimulating prostatic adenylate cyclase activity was isoproterenol greater than epinephrine approximately or equal to salbutamol greater than norepinephrine, indicating properties characteristic of beta-2-adrenergic receptor-sensitive adenylate cyclase systems. Dopamine stimulation of the enzyme was exclusively inhibited by a dopamine antagonist, haloperidol, suggesting the presence of dopamine-sensitive receptor in the prostate gland. An initial incubation of the gland with isoproterenol or dopamine resulted in a decrease in maximal enzyme activation by catecholamine, either isoproterenol or dopamine, with no change in hormone affinity. The findings that refractoriness of beta-adrenergic and dopaminergic receptor-adenylate cyclase systems was induced by both receptor-agonists suggest an interaction of an agonist-induced desensitization with another receptor or receptor-enzyme complex in the prostate gland.