Aldosterone and potassium homeostasis

The presently accepted regulators of the homeostatic excretion of potassium are the plasma concentrations of aldosterone and potassium. Evidence for a role of aldosterone is reviewed, and it is pointed out that aldosterone is kaliuretic at supraphysiologic levels but has little kaliuretic activity within its normal secretory range. Elevation of plasma potassium above its normal range enhances the kaliuretic action of aldosterone. Elevation of plasma potassium above, but not within, its normal range is strongly kaliuretic. In sheep the kaliuresis induced by intake of a potassium rich meal cannot be explained by changes in aldosterone or plasma potassium. A kaliuretic reflex arising from receptors in the gut, portal vein or liver has been proposed the explain the meal-induced kaliuresis. This putative reflex involves the central nervous system and efferent kaliuretic factors other than aldosterone and plasma potassium. Evidence for the involvement of the central nervous system and undetermined kaliuretic regulatory factors can be found in studies of the physiologic circadian rhythm of renal potassium excretion. This rhythmic excretion does not appear to depend on changes in either aldosterone or plasma potassium.