Sodium-coupled bicarbonate transporters.

Together, the Na(+)-coupled HCO(3)(-) transporters and the AE family of anion exchangers (i.e., Cl-HCO3 exchangers) comprise the bicarbonate transporter (BT) superfamily. Virtually all BTs are important for the regulation of intracellular pH (pH(i)) in cells throughout the body. Specific BTs also play roles in cell-volume regulation, as well as for the transport of salt and/or acid-base equivalents across many epithelia. Electrogenic Na/HCO3 cotransporters (NBCe's) play key roles in HCO(3)(-) reabsorption by the renal proximal tubule, and HCO(3)(-) secretion by the pancreatic duct. Electroneutral NBC's (NBCn's) regulate pH(i) in vascular smooth muscle and are present in/near axons in the brain. Finally, the Na(+)-driven Cl-HCO3 exchanger (NDCBE's) appear to be the major pH(i) regulators in CNS neurons. A characteristic of most, but not all, BT's is that they are inhibited rather effectively by 4,4'-diisothiocyanostilbene-4,4'-disulfonate (DIDS).