Studies on cyclic nucleotides in the adrenal gland. VIII. Effects of angiotensin on adenosine 3',5'-monophosphate and steroidogenesis in the adrenal cortex.

Effects of angiotensin II on corticoid biogenesis and cAMP levels in the zona fasciculata-reticularis (the decapsulated fraction) and the zona glomerulosa (the capsular fraction) from the rat adrenal gland have been studied. Angiotensin II exclusively stimulated steroidogenesis in the zona glomerulosa without stimulation of the cAMP system, suggesting that steroidogenic action of this polypeptide does not involve the adenylate cyclase system. Angiotensin II was also found to stimulate cAMP-phosphodiesterase activity in the zona glomerulosa. An elevation of calcium concentration in the incubation medium has been observed to be effective in stimulating the production of aldosterone and cAMP by the capsular fraction. Angiotensin II caused a significant enhancement of the steroidogenic response of the capsular fraction to increasing calcium concentration regardless of the response of the cAMP system to calcium. This steroidogenic effect of angiotensin II was completely abolished by calcium antagonists added to the incubation medium without any inhibitory effect on the calcium-induced accumulation of tissue cAMP. These results suggest that angiotensin II acts on the adrenal II acts on the adrenal glomerulosa cell to increase intracellular calcium, which in turn directly stimulates steroidogenesis concomitant with the increased activity of phosphodiesterase.