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KMID : 0811719990030050529
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Korean Journal of Physiology & Pharmacology
1999 Volume.3 No. 5 p.529 ~ p.538
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Effect of Ethanol on Na+ -Pi Uptake in Opossum Kidney Cells: Role of Membrane Fluidization and Reactive Oxygen Species
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In Ho Park
Moon Young Hwang/Jae Suk Woo/Jin Sup Jung/Yong Keun Kim
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Abstract
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This study was undertaken to examine the effect of ethanol on Na+?dependent phosphate (Na+?Pi) uptake in opossum kidney (OK) cells, an established renal proximal tubular cell line. Ethanol inhibited ^Na^+-dependent$ component of phosphate uptake in a dose-dependent manner with I50 of 8.4%, but it did not affect Na+?independent component. Similarly, ethanol inhibited Na+?dependent uptakes of glucose and amino acids (AIB, glycine, alanine, and leucine). Microsomal Na+?K+?ATPase activity was not significantly altered when cells were treated with 8% ethanol. Kinetic analysis showed that ethanol increased Km without a change in Vmax of Na+?Pi uptake. Inhibitory effect of n-alcohols on Na+?Pi uptake was dependent on the length of the hydrocarbon chain, and it resulted from the binding of one molecule of alcohol, as indicated by the Hill coefficient (n) of 0.8-1.04. Catalase significantly prevented the inhibition, but superoxide dismutase and hydroxyl radical scavengers did not alter the ethanol effect. A potent antioxidant DPPD and iron chelators did not prevent the inhibition. Pyrazole, an inhibitor of alcohol dehydrogenase, did not attenuate ethanol-induced inhibition of Na+?Pi uptake, but it prevented ethanol-induced cell death. These results suggest that ethanol may inhibit Na+?Pi uptake through a direct action on the carrier protein, although the transport system is affected by alterations in the lipid environment of the membrane.
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KEYWORD
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Alcohol, Na-Pi, uptake, Antioxidants, Radical scavengers, Renal epithelial cells,
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