AJP - Lung Cellular and Molecular Physiology, Vol 267, Issue 6 649-L659, Copyright © 1994 by American Physiological Society
Oxidant stress decreases Na+/H+ antiport activity in bovine pulmonary artery endothelial cells
M. Cutaia and N. Parks
Veterans Affairs Medical Center, Pulmonary Disease Division, Providence, Rhode Island 02908.
We determined the effects of oxidant stress by the use of tert-butyl
hydroperoxide (t-BOOH) on Na+/H+ exchange in pulmonary artery endothelial
cells. Monolayers were exposed to the hydroperoxide, followed by
measurement of intracellular pH and the rate of recovery from acidosis by
utilizing the pH-sensitive probe 2',7'-bis(carboxyethyl)-5(6)-
carboxyfluorescein. t-BOOH (0.4 mM) decreased the rate of acid recovery
after a 2-h exposure without evidence of overt cytotoxicity (51Cr-release
assay). Glutathione repletion (N-acetyl-L-cysteine) abolished the effect of
the hydroperoxide. Lowering intracellular glutathione with buthionine
sulfoximine decreased the acid recovery rate at a dose of t-BOOH (0.04 mM)
that was not normally associated with a change in this parameter.
Preincubation with vitamin E had no protective effect. Dithiothreitol
abolished the effect of the hydroperoxide, suggesting oxidation of protein
sulfhydryl groups as a mechanism for the altered kinetics of acid recovery.
There was no difference in cell buffering capacity between control and
treated monolayers. The findings suggest that the decrease in Na+/H+
antiport activity in this model of oxidant stress represents an early
perturbation of membrane function and illustrate the role of the
glutathione redox system in maintaining the functional integrity of the
Na+/H+ antiport in these cells.
