Characterization of Luminal and Peritubular Membrane K+ Selectivity in Proximal Tubular Cells of Frog Kidney
Abstract: The functional significance of/KCNQ1/KCNE1 K+ secretory fluxes and the effects of 3 ?mol/L Cd2+ on the peritubular cell membrane potential and its potassium selectivity were investigated in proximal tubular cells of the frog kidney. Perfusing the lumen with l-phenylalanine plus/minus chromanol 293B, a specific blocker of KCNQ1, did not modify rapid depolarization and rate of slow repolarization of the peritubular cell membrane. Peritubular exposure to Cd2+ led to a sustained, reversible hyperpolarization of the peritubular membrane, paralleled by an increase in fractional K+ conductance. Peritubular barium blunted hyperpolarization of the peritubular cell membrane to Cd2+. Thus, the KCNQ1/KCNE1 K+ secretory fluxes are absent in proximal tubule of frog kidney, while Cd2+ increases K+ selectivity of the peritubular cell membrane.
k+ selectivity frog kidney cell membrane potential chromanol 293b cadmium /kcnq1/kcne1