Steady state aldosterone dose-response relationships.

The steady state effects of different infusion rates of aldosterone on plasma concentrations of sodium and potassium, plasma renin activity, sodium space, and mean arterial pressure were determined. Measured amounts of aldosterone were infused continuously into adrenalectomized dogs for 13 weeks. Four rates of aldosterone administration were used: 16 +/- 1 mug/day, 48 +/- 3 mug/day (approximately the normal secretory rate for 22-kg dogs on a daily sodium intake of 27 mEq, potassium intake of 27 mEq), 91 +/- 4 mug/day, and 219 +/- 10 mug/day. Each rate of infusion was continued until the dogs were in sodium and potassium balance and measured variables were steady. Decreasing the rate of aldosterone administration below normal led to sharp decreases in plasma sodium concentration and sodium space, while raising the rate above normal had little effect. Plasma potassium concentration varied inversely and significantly with changes in aldosterone administration over the entire range of rates. Plasma renin activity rose extremely rapidly as the level of aldosterone fell below normal and went to zero at aldosterone infusion rates slightly above normal. Arterial pressure increased as aldosterone rose above normal but did not fall below normal at subnormal aldosterone levels, probably because of the pressor effects of simultaneously generated angiotensin II.