Effect of aldosterone on potassium excretion during potassium chloride infusion in sheep.

Experiments were performed on normal mature ewes to quantitate the effect of acute variations in aldosterone activity on renal K excretion. Six-hour clearance studies were performed on three sheep. Treatments were control (no infusion), infusion of KCl (140 meq in 2 h) alone or with superimposed infusions of aldosterone (20 micrograms/h), or infusion of aldosterone antagonist potassium canrenoate (100 mg/h). During KCl infusion there were simultaneous increases in plasma K, K excretion, and Na excretion. Aldosterone treatment diminished the increase in plasma K and in Na excretion but increased the rate of K excretion. Canrenoate had opposite effects. The rate of change of K excretion relative to the change in plasma K was 417 for aldosterone and 102 microeq/min per meq/l for canrenoate treatments, P less than 0.05. Before KCl infusion aldosterone decreased the rate of Na excretion and the salivary Na-to-K ratio but did not alter plasma K or K excretion. Aldosterone has a potent kaliuretic action in sheep when plasma K is elevated.