Urinary acid-base status

Urinary acid-base status refers to the physiological process by which the kidneys regulate urine pH and composition to maintain systemic acid-base homeostasis, primarily through bicarbonate reabsorption, net acid excretion, and generation of new bicarbonate. This involves proximal tubule mechanisms like H+ secretion via NHE3 and carbonic anhydrase to reclaim nearly all filtered bicarbonate, alongside ammonia production from glutamine metabolism and excretion of titratable acids such as phosphate buffers. In the distal nephron, alpha-intercalated cells use H+-ATPase pumps for further acidification, while beta-intercalated cells handle bicarbonate secretion during alkalosis. Dysregulation contributes to disorders like metabolic acidosis or renal tubular acidosis, where impaired ammonium excretion or H+ secretion leads to positive urinary anion gaps and systemic acidemia. Unlike molecular targets such as receptors or enzymes, this is a functional physiological state influenced by hormones like PTH, aldosterone, and endothelin, rather than directly modulated by drugs. Daily, kidneys excrete 40-50 mmol of acid mainly as ammonium (50-66% of net acid excretion), adapting to dietary or metabolic acid loads.

Other names

Renal acid-base regulationRenal acid-base homeostasisKidney acid-base balance