title: Bicarbonate/chloride antiport in Vero cells: II. Mechanisms for bicarbonate-dependent regulation of intracellular pH.
abstract: The rates of bicarbonate-dependent uptake and efflux of 22Na+ in Vero cells were studied and compared with the uptake and efflux of 36Cl-. Both processes were strongly inhibited by DIDS. Whereas the transport of chloride increased approximately ten-fold when the internal pH was increased over a narrow range around neutrality, the uptake of Na+ was much less affected by changes in pH. The bicarbonate-linked uptake of 22Na+ was dependent on internal Cl- but not on internal Na+. At a constant external concentration of HCO3-, the amount of 22Na+ associated with the cells increased when the internal concentration of HCO3- decreased and vice versa, which is compatible with the possibility that the ion pair NaCO3- is the transported species and that the transport is symmetric across the membrane. Bicarbonate inhibited the uptake of 36Cl- both in the absence and presence of Na+. At alkaline internal pH, HCO3- stimulated the efflux of 36Cl- from preloaded cells, while at acidic internal pH both Na+ and HCO3- were required to induce 36Cl- efflux. We propose a model for how bicarbonate-dependent regulation of the internal pH may occur. This model implies the existence of two bicarbonate transport mechanisms that, under physiological conditions, transport OH(-)-equivalents in opposite directions across the plasma membrane.
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D002414:Cations, Monovalent; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000378:metabolism*; D002713:Chlorine; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011188:Potassium / Q000378:metabolism; D011868:Radioisotopes; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D012979:Sodium Radioisotopes; D014709:Vero Cells
chemical_list: D001639:Bicarbonates; D002352:Carrier Proteins; D002414:Cations, Monovalent; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D011868:Radioisotopes; D012979:Sodium Radioisotopes; D000643:Ammonium Chloride; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D002713:Chlorine; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium