Renal Regulation of Acid Base Balance By the Kidney

Renal Regulation of Acid Base Balance by the Kidney

The distal tubule participates both qualitatively and quantitatively in acid-base control. The majority (up to 80%) of filtered bicarbonate is reabsorbed in the proximal tubule and the remainder by the distal tubule. The absorptive mechanism for bicarbonate reabsorption in the distal tubule is similar to that of the proximal tubule, namely the formation and dissociation of carbonic acid by the enzyme carbonic anhydrase. Conversely, although there is some hydrogen ion secretion in the proximal tubule, the bulk is secreted in the distal tubule. Hydrogen ions are excreted in the final urine in combination with either ammonia or phosphates.