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 (aCli). This reduction in aCli is inhibited by removing either HCO3- or Na+ from the perfusion solution, indicating that both HCO3- and Na+ are required for Cl- movement across the basolateral cell membrane. Reducing either HCO3- or Na+ in the basolateral solution causes an increase in aCli. Thus changes in either Na+ or HCO3- chemical gradients across the basolateral cell membrane significantly affect chloride movement. Changing intracellular pH by means of NH4Cl exposure results in an increase in aCli followed by a sharp decrease when NH4Cl is removed. These changes in intracellular chloride do not occur in the absence of HCO3-. Likewise, the decrease in aCli 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 HCO3-. Our results also support the presence of a Na+/Cl- contransport mechanism on the apical cell membrane.
- Necturus proximal tubule
- basolateral chloride transport
ASJC Scopus subject areas
- Cell Biology