The goal of this protocol is to explore the determinants of shifts in adrenal and renal vascular responsiveness to AII. We studied the time course of enhanced adrenal responsiveness following a shift from a high to a low sodium intake. As another approach we compared the effectiveness of acute plasma volume expansion with saline or with a plasma volume expander, dextran, in reducing plasma renin activity and aldosterone concentration, increasing blood flow and inducing a natriuresis.