Adrenocorticotropin and cortisol-induced changes in urinary sodium and potassium excretion in man: effects of spironolactone and RU486

The role of the glucocorticoid (type II) receptor in the Na+ retention induced by cortisol is not known. The relative contribution of mineralocorticoid (type I) and type II receptor activation to changes in urinary Na+ and K+ excretion in man was studied using spironolactone and RU486 to inhibit type I and II receptors, respectively. Normal men eating a constant daily diet received either ACTH or cortisol for 5 days. Spironolactone (400 mg/day) inhibited ACTH (80 U/day)-induced kaliuresis, but not the Na+ retention produced by ACTH or cortisol (240 mg/day) and only blunted the modest Na+ retention induced by cortisol (120 mg/day). RU486 (1200 mg/day for the first 2 day) inhibited the first day kaliuresis and carbohydrate intolerance produced by cortisol, but did not affect the Na+ retention. Thus, the kaliuresis produced by cortisol and ACTH can be attributed to type II and type I receptor activation, respectively. The failure of RU486 to inhibit the Na+ retention induced by cortisol with evidence of adequate blockade of type II receptors indicates that the Na+ retention produced by cortisol is not mediated by type II receptor activation, but is, at least in part, mediated by the type I receptor.