HYDROGEN-PEROXIDE STIMULATES SODIUM-POTASSIUM PUMP ACTIVITY IN CULTURED PULMONARY ARTERIAL ENDOTHELIAL-CELLS

Citation
Jv. Meharg et al., HYDROGEN-PEROXIDE STIMULATES SODIUM-POTASSIUM PUMP ACTIVITY IN CULTURED PULMONARY ARTERIAL ENDOTHELIAL-CELLS, The American journal of physiology, 265(6), 1993, pp. 120000613-120000621
Citations number
36
Categorie Soggetti
Physiology
ISSN journal
00029513
Volume
265
Issue
6
Year of publication
1993
Part
1
Pages
120000613 - 120000621
Database
ISI
SICI code
0002-9513(1993)265:6<120000613:HSSPAI>2.0.ZU;2-4
Abstract
Oxidant injury to pulmonary vascular endothelium is an important facto r in the pathogenesis of acute lung injury. Oxidant injury to other ce ll types has been reported to alter the function of Na-K-adenosinetrip hosphatase (ATPase) an enzyme important in maintenance of cellular ion ic homeostasis and in transport of ions across biological membranes. W e investigated the effect of H2O2 (0.001-10 mM) or xanthine (X) (15.2 mug/ml) plus xanthine oxidase (XO) (0.0153 U/ml) on the Na-K pump acti vity of cultured bovine pulmonary arterial endothelial cells (PAECs). We used a functional assay, using (RbCl)-Rb-86 as a tracer for K+ and expressing Na-K pump activity as ouabain-inhibitable K+ uptake. Our re sults demonstrate that H2O2 and X/XO stimulate Na-K pump activity of b ovine PAECs, an effect prevented by catalase. In addition, we assessed the affinity, number, and turnover of [H-3]ouabain binding sites on i ntact endothelial monolayers and found that H2O2 increased affinity to [H-3]ouabain, decreased the number of binding sites, and increased th e rate of pump turnover. Influx of Na-22 increased in response to a no nlytic concentration of H2O2. Cell injury, as assessed by Cr-51 releas e, adherent cell number, and phase-microscopic morphology, was not obs erved after 30-min incubations with the lowest dose (1 mM) of H2O2 eff ective in stimulating Na-K pump activity, or after incubation with X/X O. Na-K pump inhibition by ouabain significantly increased the Cr-51 r elease caused by H2O2 or by X/XO, suggesting that the increase in Na-K pump activity may be a compensatory response to the cellular alterati ons produced by H2O2. Incubation with H2O2 decreased cell ATP content, an effect which was not prevented by coincubation with ouabain. In su mmary, these results show that H2O2 increases Na-K pump activity of PA ECs, an effect mediated, at least in part, by increased intracellular [Na] and by an increased rate of pump turnover. It is possible that th e increased pump activity may be an early marker of endothelial cell p erturbation.