Effects of ethanol on GLUT1 protein and gene expression in rat astrocytes

Effects of ethanol on glucose transporter gene expression were examined in cultured rat astrocytes. Exposure to 50 or 100 mM ethanol for 18 hours significantly inhibited hexose uptake and reduced the number of glucose transporters, as indicated by binding studies with cytochalasin B. Indirect immunofluorescence and immunoperoxidase staining showed marked reduction of the GLUT1 glucose transporter by exposure to 100 mM ethanol for 5 or 18 hours, but no obvious change in response to 50 mM ethanol. Western blot analysis showed GLUT1 protein levels to be decreased by 52 +/- 12% (p < 0.05) after exposure to 100 mM ethanol for 18 hours. In situ hybridization histochemistry indicated an increase in steady-state GLUT1 mRNA in astrocytes exposed to 50 or 100 mM ethanol for 5 or 18 hours. Quantitation of GLUT1 mRNA levels by northern blot analysis showed that GLUT1 mRNA levels were increased by 59 and 112% in cells treated for 5 h with 50 and 100 mM ethanol, respectively. A similar effect was observed after treatment for 18 hours, but ethanol did not alter actin gene expression. Experiments using actinomycin D to block RNA synthesis suggest that this increase in steady-state mRNA level results from increased message stability. These results suggest that ethanol acts on GLUT1 gene expression at the post-transcriptional level.