Effect of aldosterone on renal potassium conservation in the rat.

The importance of reduced plasma aldosterone concentration (PAC) in renal potassium (K) conservation is unclear. Thus we examined the effect of aldosterone on incipient, developing, and established renal K conservation. Adrenalectomized (ADX) dexamethasone-replaced rats were continuously treated with high, normal, or low dosages of aldosterone during 4 days of dietary K restriction and were compared with rats without aldosterone replacement. High and normal aldosterone replacement reduced the fall in urinary K excretion and led to significantly lower plasma [K], skeletal muscle tissue K content, renal tissue K content, and greater negative cumulative balance of K compared with low aldosterone replacement. Likewise, plasma [K] and skeletal muscle tissue K content were significantly less in intact rats after 3 days of K deprivation and chronic treatment with aldosterone. Acute aldosterone treatment significantly increased urinary K excretion by isolated perfused kidneys. We conclude that incipient, developing, and established renal K conservation is not independent of mineralocorticoid activity and that the rapid fall in PAC during K depletion is necessary for maximal renal K conservation.