This program is directed at the elucidation of the role of the renin-angiotensin system and other factors in the regulation of aldosterone secretion by the zone glomerulosa of the adrenal gland. Specific areas of research include the characterization and regulation of angiotensin II receptors, the actions of angiotensin II and other regulators of aldosterone secretion, and the production and metabolism of angiotensin II. Major emphasis has been placed upon the use of enzyme-dispersed adrenal cells for analysis of the relations between angiotensin II receptors and aldosterone production, and the interactions between angiotensin II and other factors such as ACTH, sodium and potassium levels. The effects of altered electrolyte balance on adrenal receptors and steroid responses are studied, in particular the effects of sodium intake on the concentration and affinity of angiotensin II receptors in adrenal and smooth muscle cells. These studies are designed to clarify the control of adrenal and vascular sensitivity to angiotensin II during sodium deficiency, the mechanisms by which angiotensin II regulates the concentration of its receptors in adrenal and smooth muscle, and the activation pathways that are initiated by occupancy of angiotensin II receptors.