Metabolic acidosis and parathyroidectomy increase Na+-H+ exchange in brush border vesicles

Na+-H+ exchange across the brush border membrane of the renal proximal tubular cell is a mechanism for Na+ reabsorption and H+ secretion. An electroneutral Na+-H+ exchange activity has been identified in isolated renal brush border membrane vesicles from rat and dog kidney, and increased Na+-H+ exchange has been measured in brush border membrane vesicles from remnant kidneys of dogs with chronic renal failure. To ascertain whether changes in H+ secretion by the kidney observed in chronic metabolic acidosis and in states of altered parathyroid function might result from altered Na+-H+ exchange across the renal cortical cellular brush border membrane, we measured Na+-H+ exchange in brush border membrane vesicles from kidneys of dogs with chronic metabolic acidosis and from kidneys of thyroparathyroidectomized dogs. Increased amiloride-sensitive Na+-H+ exchange was demonstrated in brush border membrane vesicles from kidneys of both groups of dogs, suggesting that adaptations in H+ excretion in chronic metabolic acidosis and hypoparathyroidism might be explained by increased activity of a renal brush border membrane Na+-H+ exchanger.