Renal chloride-bicarbonate exchangers

This review discusses the molecular identities and functional properties of sodium-independent Cl(-)-HCO3- exchangers in the kidney. The main sites of renal Cl(-)-HCO3- exchange are in the intercalated cells of the collecting duct. The function of Cl(-)-HCO3- exchange is to provide a pathway for base efflux to balance the ATP-driven H+ efflux in cells that carry out transcellular net transport of H+. In the alpha-intercalated cell, which secretes H+ into the lumen, there is now excellent evidence that the basolateral Cl(-)-HCO3- exchanger is an N-terminal truncated form of the erythrocyte anion exchanger 1 (band 3) protein. In the beta-intercalated cell, which secretes HCO3-, it is well established that there is a Cl(-)-HCO3- exchanger in the apical membrane. Functional, immunocytochemical, and biochemical evidence indicate that the apical Cl(-)-HCO3- exchanger is not a product of the anion exchanger 1 gene. The identity of this protein remains uncertain.