In vitro ethanol effects on the transport properties of isolated renal brush-border membrane vesicles
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Thein vitro effect of ethanol on membrane structure and transport properties was studied in isolated renal brush border membrane vesicles.31P-NMR studies showed a dose-dependent increase in the quantity of an isotropic, possibly inverted-micellar component of the renal brush-border membrane as a result of treatment with ethanol. Such structures have been shown to be instrumental in the translocation of material across membrane bilayers. A23Na-NMR study of Na+ exchange in artificial phosphatidylcholine liposomes indicated that ethanol (0.1%) was capable of rending the otherwise inert vesicles permeable to sodium, supporting the idea that ethanol may exert its action via a direct effect on the structure of the phospholipid bilayer. In the isolated renal brush-border membrane vesicles, like in the artificial liposomes, amiloride-insensitive pathways of Na+ transport were shown to be markedly activated by ethanol. These results were consistent with the inhibitory effect ethanol had on Na+ gradient-dependent transport systems such as the Na+ gradient-dependentd-glucose transport and Na+/H+ exchange. In conclusion, our results indicate that ethanol exerts its effect on the renal brush-border membrane by causing a structural change in the phospholipid bilayer which activates sodium intake. The inhibitory effect of ethanol on glucose uptake and Na+/H+ exchange is secondary, as a result of the dissipation of the energy-producing Na+ gradient.
Key Wordsrenal brush-border membrane kidney ethanol transport 31P-NMR 23Na-NMR
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- Boni, L.T., Stewart, T.P., Alderfer, J.L., Hui, S.W., 1981. Lipid-polyethylene glycol interactions: II. Formation of defects in bilayers.J. Membrane Biol. 62:71–77Google Scholar
- Chin, J.H., Goldstein, D.B. 1976. Drug tolerance in biomembranes: A spin label study of the effects of ethanol.Science 196:684–685Google Scholar
- Cullis, P.R., McLaughlin, A.C. 1977. Phosphorus nuclear magnetic reasonance studies of model and biological membranes.Trends Biochem. Sci. 2:196Google Scholar
- Elgavish A., Rifkind, J., Sacktor, B. 1983.In vitro effects of vitamin D3 on the phospholipids of isolated renal brush border membranes.J. Membrane Biol. 72:85–91Google Scholar
- Freiberg M.M., Kinsella, J., Sacktor, B. 1983. Glucocorticoids increased the Na+−H+ exchange and decreased the Na+ gradient-dependent phosphate uptake systems in renal brush border membrane vesicles.Proc. Natl. Acad. Sci. USA 79:4932–4936Google Scholar
- Morgan, M.Y. 1982. Alcohol and nutrition.Br. Med. B. 38:21Google Scholar
- Sacktor, B. 1977. Transport in membrane vesicles isolated from the mammalian kidney and intestine.In: Current Topics in Bioenergetics. Vol. 6, pp. 39–81. Academic, New York-San Francisco-LondonGoogle Scholar
- Sargent, W.Q., Simpson, J.R., Beard, J.D. 1977. Renal bicarbonate metabolism after a single ethanol dose.Fed. Proc. 36:332Google Scholar