title: Chloride transport across the basolateral cell membrane of the Necturus proximal tubule: dependence on bicarbonate and sodium.
abstract: The transport of chloride across the Necturus proximal tubule cell was studied in the doubly-perfused kidney using conventional, chloride-sensitive and pH-sensitive microelectrodes. Lowering chloride activity in the basolateral solution results in a reduction in intracellular Cl- activity (aiCl). This reduction in aiCl is inhibited by removing either HCO-3 or Na+ from the perfusion solution, indicating that both HCO-3 and Na+ are required for Cl- movement across the basolateral cell membrane. Reducing either HCO-3 or Na+ in the basolateral solution causes an increase in aiCl. Thus changes in either Na+ or HCO-3 chemical gradients across the basolateral cell membrane significantly affect chloride movement. Changing intracellular pH by means of NH4Cl exposure results in an increase in aiCl followed by a sharp decrease when NH4Cl is removed. These changes in intracellular chloride do not occur in the absence of HCO-3. Likewise, the decrease in aiCl following NH4Cl treatment requires the presence of Na+ in the basolateral solution. We conclude that chloride is transported across the basolateral cell membrane in exchange for both Na+ and HCO-3. Our results also support the presence of a Na+/Cl- cotransport mechanism on the apical cell membrane.
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D005260:Female; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D009337:Necturus; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology*
chemical_list: D001639:Bicarbonates; D002712:Chlorides; D000643:Ammonium Chloride; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D012964:Sodium; D011188:Potassium