Hydrogen ion currents in rat alveolar epithelial cells.
Alveolar epithelial cells isolated from rats and maintained in primary culture were studied using the whole-cell configuration of the "patch-clamp" technique. After other ionic conductances were eliminated by replacing permeant ions with N-methyl-D-glucamine methanesulfonate, large voltage-activated hydrogen-selective currents were observed. Like H+ currents in snail neurons and axolotl oocytes, those in alveolar epithelium are activated by depolarization, deactivate upon repolarization, and are inhibited by Cd2+ and Zn2+. Activation of H+ currents is slower in alveolar epithelium than in other tissues, and often has a sigmoid time course. Activation occurs at more positive potentials when external pH is decreased. Saturation of the currents suggests that diffusion limitation may occur; increasing the pipette buffer concentration from 5 to 120 mM at a constant pH of 5.5 increased the maximum current density from 8.7 to 27.3 pA/pF, indicating that the current amplitude can be limited in 5 mM buffer solutions by the rate at which buffer molecules can supply H+ to the membrane. These data indicate that voltage-dependent H+ currents exist in mammalian cells.
DeCoursey
T E
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Department of Physiology, Rush Presbyterian St. Luke's Medical Center, Chicago, Illinois 60612.
D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D004594:Electrophysiology; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism*; D011522:Protons; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism*; D051381:Rats
D007473:Ion Channels; D011522:Protons