Oxidant stress alters Na+ pump and Na(+)-K(+)-Cl- cotransporter activities in vascular endothelial cells.
We have previously shown that oxidant stress activates Ca(2+)-dependent K+ efflux in pulmonary vascular endothelial cells. The present study was performed to determine the effect of oxidant stress on Na+ and K+ homeostasis using the radiotracers, 22Na+ and 86Rb+. Cellular ion contents at equilibrium were determined after incubation of cells with tert-butyl hydroperoxide (t-BOOH; 0.4 mM) for various durations. Cell content of 86Rb+ was unchanged through incubation periods of 2 h but was significantly decreased at 3 h, whereas cell content of 22Na+ progressively increased with increasing incubation duration. The effect of t-BOOH on Na+ pump and Na(+)-K(+)-Cl- cotransporter activities was examined via measurement of 86Rb+ influx in the absence or presence of ouabain and bumetanide, respectively. Oxidant stress time dependently increased ouabain-sensitive 86Rb+ influx, with little alteration in specific ouabain binding. In contrast, bumetanide-sensitive 86Rb+ influx was decreased by incubation with the oxidant. These findings suggest that the oxidant-induced increase in cellular Na+ content is associated with increased plasmalemmal Na(+)-K(+)-adenosinetriphosphatase activity. Furthermore, inward ion movement via the bumetanide-sensitive pathway is decreased, suggesting that oxidant stress inhibits the Na(+)-K(+)-Cl- cotransporter.
Elliott
S J
SJ
Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030.
Schilling
W P
WP
D000225:Adenine / Q000378:metabolism; D002034:Bumetanide / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D010042:Ouabain / Q000378:metabolism / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology*; D010545:Peroxides / Q000494:pharmacology*; D011651:Pulmonary Artery / Q000166:cytology / Q000378:metabolism; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects*; D020122:tert-Butylhydroperoxide
D002352:Carrier Proteins; D016877:Oxidants; D010545:Peroxides; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D010042:Ouabain; D020122:tert-Butylhydroperoxide; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D000225:Adenine; D012413:Rubidium