Factors influencing transepithelial potential difference in mammalian distal tubule

Studies were performed to examine some electrical properties of the mammalian distal tubule. Experiments were performed to evaluate the influence of changes in ion concentration in luminal fluid on transepithelial potential difference. Variations in the concentration of Na+ and K+, near the physiologic range, resulted in only modest changes in potential difference. During changes in Na+ the average slope, deltaV/ln C2/C1, was -1.52 +/- 0.39 mV and during variations in K+ the slope was -5.60 +/- 0.95 mV. Changes in Cl- concentration had no effect on transepithelial potential difference. Since the sum of transferase numbers did not equal 1, it seems likely that potential difference is influenced by a shunt current due to cellular rheogenic pumps. These data, therefore, indicate that variations in ion concentration in tubular fluid of the mammalian distal tubule do not significantly influence the resting transepithelial potential difference, and they suggest that analysis of permselective properties of the luminal cell membrane by transepithelial electrophysiologic approaches is probably invalid.