Characterization of luminal and peritubular membrane K+ selectivity in proximal tubular cells of frog kidney.
The functional significance of KCNQ1/KCNE1 K(+) secretory fluxes and the effects of 3 micromol/L Cd(2+) 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 Cd(2+) 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 Cd(2+). Thus, the KCNQ1/KCNE1 K(+) secretory fluxes are absent in proximal tubule of frog kidney, while Cd(2+) increases K(+) selectivity of the peritubular cell membrane.
Nesović
Jelena
J
Department of Pathological Physiology, Medical Faculty, Belgrade, Serbia and Montenegro.
Cemerikić
Dusan
D
D000818:Animals; D001464:Barium / Q000494:pharmacology; D002104:Cadmium / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D002839:Chromans / Q000494:pharmacology; D004594:Electrophysiology; D051656:KCNQ Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D051657:KCNQ1 Potassium Channel / Q000187:drug effects / Q000378:metabolism*; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D010649:Phenylalanine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011898:Ranidae / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology
D002839:Chromans; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D013449:Sulfonamides; D002104:Cadmium; C103474:6-cyano-4-(N-ethylsulfonyl-N-methylamino)-3-hydroxy-2,2-dimethylchromane; D001464:Barium; D010649:Phenylalanine; D011188:Potassium