AJP - Cell Physiology, Vol 259, Issue 4 C586-C598, Copyright © 1990 by American Physiological Society
ATP-dependent pHi recovery in lung macrophages: evidence for a plasma membrane H(+)-ATPase
A. Bidani and S. E. Brown
Department of Internal Medicine, University of Texas Medical Branch, Galveston 77550.
We have previously shown that cytoplasmic pH (pHi) recovery in pulmonary
macrophages, under nominally HCO3(-)-free conditions, after acute
intracellular acidification is Na+ and amiloride insensitive and is blocked
by nonspecific proton adenosinetriphosphatase (ATPase) inhibitors
N-ethyl-maleimide and N,N'-dicyclohexylcarbodiimide [Am. J. Physiol. 257
(Cell. Physiol. 26): C65-C76, 1989]. To further delineate the mechanism of
H+ extrusion across plasma membranes of pulmonary macrophages, we
investigated the effects of metabolic inhibitors of oxidative
phosphorylation and glycolysis on cellular ATP content and pHi recovery
from an intracellular acid load under nominally HCO3(-)-free conditions.
Dose-dependent reductions in ATP levels and in the rate of pHi recovery
were obtained in the presence of KCN (50% inhibition, 10(-4) M). Parallel
reductions in ATP content and the rate of pHi recovery were noted in the
presence of antimycin A, rotenone, oligomycin, and iodoacetate. However,
inhibition by iodoacetate was reduced in the presence of pyruvate. The more
specific vacuolar H(+)-ATPase inhibitors, bafilomycin A1 and
7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, resulted in no decrement in
cellular ATP levels but significantly inhibited pHi recovery. These studies
demonstrate that recovery from an acid load is ATP dependent and provide
support for a plasmalemmal proton ATPase, perhaps of the vacuolar type,
that participates in regulation of pHi in pulmonary macrophages.
