Role of the kidney in controlling acid-base balance

The kidney is responsible for the maintenance of an important sector of the regulation of acid-base balance, i.e., that related to the maintenance of the alkaline reserve of the body and to excretion of fixed acids. In this review, the basic mechanisms of H-ion secretion along the nephron, responsible for bicarbonate reabsorption, titratable acid formation and ammonia excretion, are discussed. The mechanisms responsible for tubule acidification along proximal tubule, thick ascending limb, cortical distal tubule and collecting duct are reviewed, having in mind the function of the apical and basolateral membranes. Finally, the pathophysiological aspects of urinary acidification are discussed, focusing on renal tubular acidosis models (induced by maleate and amphotericin B treatment) and their cellular mechanisms, as well as the role of adrenal steroids in urinary acidification.