Renal potassium adaptation in the rat: role of glucocorticoids and aldosterone.

This study examines the role of adrenocortical hormones in the kaliuresis following an acute intragastric KCl load in conscious control (CK) and high potassium diet (HK) rats. Adrenalectomy, 1 day before test, reduced K+ excretion by 35% in CK and 60% in HK rats, leading to minimal differences in K excretion between CK and HK. By contrast, spironolactone inhibited K excretion by only 10%. Glucocorticoids (dexamethasone 3-10 micrograms/100 g) increased K+ excretion in adrenalectomized CK and to a greater extent in adrenalectomized HK rats. Aldosterone (3 micrograms/100 g) alone had a variable effect on urinary potassium excretion in adrenalectomized rats. A combination of dexamethasone (3 micrograms/100 g) and aldosterone (3 micrograms/100 g) in adrenalectomized rats induced potassium excretion equivalent to that in intact rats. Adrenalectomized HK rats had a greater kaliuretic response to dexamethasone and aldosterone than CK rats. These results 1) demonstrate a role for glucocorticoids in K+ excretion in HK rats and 2) illustrate the importance of the increased responsiveness to both glucocorticoids and mineralocorticoids in potassium adaptation.