1. The renal response to aldosterone (urinary sodium and potassium excretion) was determined in adrenalectomized rats previously fed either a high potassium diet or a control diet. High K+ rats showed an enhanced response to aldosterone at all doses tested.
2. This enhanced response to aldosterone required the presence of the adrenal glands during the induction period, could be suppressed by a high sodium intake, but could not be induced by a low sodium diet.
3. No difference between high K+ and control rats could be detected in renal mineralocorticoid receptors, assessed by both in vivo and in vitro binding of tritiated aldosterone.
4. The method of the induction, and the mechanism of the enhanced response, remain to be defined.