Basolateral membrane H-OH-HCO3 transport in the proximal tubule.
This review focuses on the basolateral membrane mechanisms of H-OH-HCO3 transport in the proximal tubule. The mechanism that has the greatest transport capacity and mediates most of transepithelial H-HCO3 transport is the electrogenic, Na-3HCO3 cotransporter. This transporter has been extensively characterized in the salamander, rat, and rabbit proximal tubule, and has now been found in a number of other epithelia that effect transepithelial NaHCO3 transport. Transporter rate is sensitive to intra- and extracellular [Na], intra- and extracellular [HCO3]/pH, and cell voltage. Adaptations in transporter activity have been demonstrated in chronic metabolic acidosis and alkalosis, chronic respiratory acidosis and alkalosis, and chronic hyperfiltration. In addition to the Na-3HCO3 cotransporter, the basolateral membrane possesses both Na-dependent and -independent Cl-HCO3 exchangers, a H leak, and in the S3 proximal tubule an Na-H antiporter. The role of these H-OH-HCO3 transport mechanisms in transcellular HCO3 and Cl absorption and pHi defense is discussed.
Preisig
P A
PA
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 77235-8856.
Alpern
R J
RJ
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport; D001696:Biomechanical Phenomena; D002352:Carrier Proteins / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism; D008566:Membranes / Q000378:metabolism; D027982:Sodium-Bicarbonate Symporters; D017923:Sodium-Hydrogen Exchangers
D001639:Bicarbonates; D002352:Carrier Proteins; D002712:Chlorides; D027982:Sodium-Bicarbonate Symporters; D017923:Sodium-Hydrogen Exchangers; D006859:Hydrogen