Na+-H+ exchange activity in renal brush border membrane vesicles in response to metabolic acidosis: The role of glucocorticoids.

Amiloride-sensitive Na+ -H+ exchange activity in brush border membrane vesicles isolated from rat proximal tubule was increased in metabolic acidosis. The enhancement of exchange activity required an intact adrenal gland or glucocorticoid supplements. Ammonium and phosphate excretions were increased during acidosis and these were also largely dependent on an intact adrenal gland or glucocorticoid supplements. Amiloride-insensitive Na+ uptake and passive H+ permeability were not altered by acidosis or the glucocorticoid status of the animal. These findings are consistent with glucocorticoids having an important regulatory role in the kidney by orchestrating the proximal tubular adaptation to metabolic acidosis.