CHRONIC AND ACUTE ETHANOL TREATMENT MODIFIES FLUIDITY AND COMPOSITIONIN PLASMA-MEMBRANES OF A HUMAN HEPATIC CELL-LINE (WRL-68)

The aim of this study was to compare the effects of chronic (0.1 mol/L ethanol exposure during 30 days) and acute (0.5 mol/L, ethanol exposu re during 24 h) ethanol treatment on the physical properties and the l ipid composition of plasma membranes of the WRL-68 cells (fetal human hepatic cell line). Using fluorescence polarization we found that etha nol treatment reduced membrane anisotropy due to disorganization of ac yl chains in plasma membranes and consequently increased fluidity, as measured with the diphenylhexatriene probe. Addition of ethanol in vit ro reduced anisotropy in control plasma membranes, whereas chronically ethanol-treated plasma membranes were relatively tolerant to the in v itro addition of ethanol. Acutely ethanol-treated plasma membranes exh ibited a smaller anisotropy parameter value than control plasma membra nes. We found a decrease in total phospholipid content in acute ethano l WRL-68 plasma membranes. Cholesterol content was increased in both e thanol treatments, and we also found a significant decrease in phospha tidylinositol and phosphatidylcholine and an increase in phosphatidyle thanolamine content in ethanol-treated plasma membranes. Our data show ed that ethanol treatment decreased the anisotropy parameter consisten tly with increased fluidity, while increasing the cholesterol/phosphol ipid ratio of plasma membranes of WRL-68 cells, but only chronically e thanol-treated plasma membranes exhibited tolerance to the in vitro ad dition of ethanol. It is important to note that some changes that were interpreted as a result of chronic ethanol treatment were also presen t in short-period ethanol treatments.