Whole-cell potassium currents in single early distal tubule cells

The apical membrane potassium conductance of amphibian early distal tubules is sensitive to changes in the intracellular pH, with cellular acidification causing a decreased conductance. With the whole-cell patch-clamp technique, we have measured the total potassium conductance of single isolated early distal tubule cells of the frog. With symmetrical potassium gluconate solutions, the whole-cell current was found to be strongly rectifying, with an inward conductance of 12.9 nS (at intracellular pH between 7.6 and 8.0) and an outward conductance of 1.0 nS. The inward current was almost totally inhibited by the addition of 10 mM Ba2+ to the bath solution. The use of pipette solutions with pH between 7.0 and 8.0 showed a positive correlation between intracellular pH and conductance. In contrast, acidification of the extracellular solution caused no significant change in conductance.