EFFECT OF ALDOSTERONE ON RENAL POTASSIUM CONSERVATION IN THE RAT

The importance of reduced plasma aldosterone concentration (PAC) in re nal potassium (K) conservation is unclear. Thus we examined the effect of aldosterone on incipient, developing, and established renal K cons ervation. Adrenalectomized (ADX) dexamethasone-replaced rats were cont inuously treated with high, normal, or low dosages of aldosterone duri ng 4 days of dietary K restriction and were compared with rats without aldosterone replacement. High and normal aldosterone replacement redu ced the fall in urinary K excretion and led to significantly lower pla sma [K], skeletal muscle tissue K content, renal tissue K content, and greater negative cumulative balance of K compared with low aldosteron e replacement. Likewise, plasma [K] and skeletal muscle tissue K conte nt were significantly less in intact rats after 3 days of K deprivatio n and chronic treatment with aldosterone. Acute aldosterone treatment significantly increased urinary K excretion by isolated perfused kidne ys. We conclude that incipient, developing, and established renal K co nservation is not independent of mineralocorticoid activity and that t he rapid fall in PAC during K depletion is necessary for maximal renal K conservation.