Adenosine 3′:5′-cyclic monophosphate production and steroidogenesis by isolated rat adrenal glomerulosa cells. Effects of angiotensin II and [Sar¹,Ala⁸]angiotensin II

Angiotensin II effects on cyclic AMP production and steroid output were studied in a sensitive preparation of isolated rat adrenal glomerulosa cells. With increasing concentrations of angiotensin II logarithmic dose–response curves for aldosterone and cyclic AMP production were similar. The minimum effective dose (0.2nm) for stimulation of aldosterone production also significantly (P<0.001) increased cyclic AMP output. For both aldosterone and cyclic AMP production, the peptide hormone concentration eliciting maximal response (0.2μm) and the ED₅₀ (median effective dose) values (1nm) were the same; this is consistent with cyclic AMP acting as an intracellular mediator for angiotensin II-stimulated aldosterone production by glomerulosa cells. The angiotensin II antagonist [Sar¹,Ala⁸]angiotensin II inhibited angiotensin II-stimulated corticosterone and aldosterone production in these cells. An equimolar concentration of antagonist halved the response to 20nm-angiotensin II, and complete inhibition was observed with 0.2μm-antagonist. In contrast, [Sar¹,Ala⁸]angiotensin II had no effect on maximally stimulated steroidogenesis induced by serotonin and a raised extracellular K⁺ concentration. Increasing concentrations of [Sar¹,Ala⁸]angiotensin II alone decreased corticosterone and aldosterone outputs significantly (P<0.05) at concentrations of 20nm and 2nm of antagonist respectively. A significant (P<0.001) decrease in cyclic AMP production occurred with 2μm antagonist and this was comparable with the decrease in aldosterone production. It is concluded that [Sar¹,Ala⁸]angiotensin II can independently affect glomerulosa-cell steroidogenesis, possibly by modulating adenylate cyclase activity.