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

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Abstract
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.