In vitro ethanol effects on the transport properties of isolated renal brush-border membrane vesicles.
The in 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. A 23Na-NMR study of Na+ exchange in artificial phosphatidylcholine liposomes indicated that ethanol (0.1%) was capable of rendering 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-dependent D-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.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000494:pharmacology*; D007672:Kidney Cortex / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008564:Membrane Potentials / Q000187:drug effects; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D013997:Time Factors
D008081:Liposomes; D000431:Ethanol; D012964:Sodium