Somatostatin modulates effects of angiotensin II in adrenal glomerulosa zone

The octapeptide angiotensin II is a major regulator of the adrenal glomerulosa zone, acting both as an acute stimulus of aldosterone secretion and as a trophic hormone which increases steroidogenic enzymes and angiotensin II receptors in glomerulosa cells. Angiotensin II also mediates the adrenal effects of altered sodium balance, and is essential for the aldosterone response to sodium restriction. However, the adrenal effects of angiotensin II are attenuated during sodium loading, suggesting that other local or humoral factors modulate its actions on adrenal glomerulosa function. Somatostatin, the somatotropin release inhibiting factor of the hypothalamus, has been shown to inhibit the secretion and action of several pituitary and non-pituitary hormones. Because somatostatin has been found in several non-neural tissues, and seems to act as a local regulator of endocrine function, we have now examined the possibility that it may also modulate the effects of angiotensin II in the adrenal glomerulosa cell. Our studies have shown that low concentrations of somatostatin specificity inhibit the production of angiotensin II-stimulated aldosterone, and that this action is mediated by specific, high-affinity receptors for somatostatin in the zona glomerulosa.