Affiliation:
1. Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois
Abstract
Voltage-gated proton channels are expressed highly in rat alveolar epithelial cells. Here we investigated whether these channels contribute to pH regulation. The intracellular pH (pHi) was monitored using BCECF in cultured alveolar epithelial cell monolayers and found to be 7.13 in nominally HCO3−-free solutions [at external pH (pHo) 7.4]. Cells were acid-loaded by the NH4+prepulse technique, and the recovery was observed. Under conditions designed to eliminate the contribution of other transporters that alter pH, addition of 10 μM ZnCl2, a proton channel inhibitor, slowed recovery about twofold. In addition, the pHiminimum was lower, and the time to nadir was increased. Slowing of recovery by ZnCl2was observed at pHo7.4 and pHo8.0 and in normal and high-K+Ringer solutions. The observed rate of Zn2+-sensitive pHirecovery required activation of a small fraction of the available proton conductance. We conclude that proton channels contribute to pHirecovery after an acid load in rat alveolar epithelial cells. Addition of ZnCl2had no effect on pHiin unchallenged cells, consistent with the expectation that proton channels are not open in resting cells. After inhibition of all known pH regulators, slow pHirecovery persisted, suggesting the existence of a yet-undefined acid extrusion mechanism in these cells.
Publisher
American Physiological Society
Subject
Cell Biology,Physiology (medical),Pulmonary and Respiratory Medicine,Physiology
Cited by
33 articles.
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