Role of Aldosterone in the Mechanism of Renal Potassium Adaptation

Chronic potassium loading results in an adaptive change in renal tubular epithelium which increases the capacity for potassium excretion. The present study was performed to evaluate the role of aldosterone in renal potassium adaptation, since hyperaldosteronism stimulates potassium secretion, and potassium loading increases the production of aldosterone. Experiments were performed in animals with intact adrenal glands, and in adrenalectomized animals (Adx) replaced with basal physiologic amounts of corticosterone, which were not replaced with aldosterone, or were chronically infused with aldosterone to achieve either basal plasma levels or elevated levels. Chronic potassium loading in adrenal intact animals was associated with a statistically significant higher rate of urinary potassium excretion (3.57 +/- 0.30 microEq/min/100 g BW) compared to the control rate (2.54 +/- 0.25 microEq/min/100 g BW, p less than 0.05), during acute infusion of KCl. In potassium loaded Adx animals, with selective replacement of adrenal hormones, the maximum rate of potassium excretion was blunted in the absence of aldosterone, compared to potassium loaded animals with intact adrenal glands. In contrast, when Adx animals were infused chronically with aldosterone, to achieve basal or elevated plasma levels, the maximum rate of potassium excretion was not blunted, although at basal aldosterone levels increased potassium excretion was due, at least in part, to hyperkalemia. These results indicate that the induction of renal potassium adaptation after a week or more of chronic potassium loading is dependent on the action of hyperaldosteronism on renal tubular epithelium.