Factor(s) released by glucose-deprived astrocytes enhance glucose transporter expression and activity in rat brain endothelial cells

Glucose transporter (GLUT) expression and regulation were studied in rat br ain endothelial cells in primary culture (RBEC) and in immortalised RBE4 ce lls. Immunoblotting analysis showed a low expression of the endothelium-spe cific GLUT1 in RBEC and RBE4 cells compared to isolated brain capillaries. RBEC and RBE4 cells also expressed the GLUT3 isoform, whereas it was not pr esent in isolated brain capillaries. No change in GLUT expression was obser ved in endothelial cells treated with astrocyte-conditioned medium. However , treatment with conditioned medium obtained from glucose-deprived astrocyt es increased endothelial GLUT1 expression and glucose uptake. These results suggest that astrocytes submitted to hypoglycaemic conditions may release factor(s) that increase glucose uptake through the blood-brain barrier. (C) 2001 Elsevier Science B,V. All rights reserved.