Intracellular pH shifts in cultured kidney (A6) cells: effects on apical Na+ transport.
We report, for the epithelial Na+ channel (ENaC) in A6 cells, the modulation by cell pH (pHc) of the transepithelial Na+ current (INa), the current through the individual Na+ channel (i), the open Na+ channel density (No), and the kinetic parameters of the relationship between I(Na) and the apical Na+ concentration. The i and N) were evaluated from the Lorentzian INa noise induced by the apical Na+ channel blocker 6-chloro-3, 5-diaminopyrazine-2-carboxamide. pHc shifts were induced, under strict and volume-controlled experimental conditions, by apical/basolateral NH4Cl pulses or basolateral arrest of the Na+/H+ exchanger (Na+ removal; block by ethylisopropylamiloride) and were measured with the pH-sensitive probe 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. The changes in pHc were positively correlated to changes in INa and the apically dominated transepithelial conductance. The sole pHc-sensitive parameter underlying INa was No. Only the saturation value of the INa kinetics was subject to changes in pHc. pHc-dependent changes in No may be caused by influencing Po, the ENaC open probability, or/and the total channel number, NT = No/Po.
Zeiske
W
W
Laboratory of Physiology, Katholieke Universiteit Leuven, Campus Gasthuisberg, B-3000 Leuven, Belgium.
Smets
I
I
Ameloot
M
M
Steels
P
P
van Driessche
W
W
D000643:Ammonium Chloride / Q000494:pharmacology; D001692:Biological Transport / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D053503:Epithelial Sodium Channels; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism*; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D007700:Kinetics; D012964:Sodium / Q000378:metabolism*; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000378:metabolism / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors
D053503:Epithelial Sodium Channels; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D017923:Sodium-Hydrogen Exchangers; D000643:Ammonium Chloride; D012965:Sodium Chloride; D006859:Hydrogen; D012964:Sodium