Expression and localization of insulin-regulatable glucose transporter (GLUT4) in rat brain.

The localization of glucose transporters (GLUTs) was examined in various regions of the rat brain. The mRNA of GLUT1 and GLUT3 were found ubiquitously in every brain region (cortex, hippocampus, midbrain, striatum, hypothalamus, medulla oblongata and cerebellum). The mRNA and protein of GLUT4, an insulin-regulatable glucose transporter in peripheral tissues, were also identified, particularly abundantly in the cerebellum. In situ hybridization analysis revealed that GLUT4 mRNA was present in some discrete cells, such as Purkinje cells in the cerebellum, the vestibular nucleus in the medulla oblongata and also in ependymal cells along the cerebral ventricles. The GLUT4 mRNA level in the cerebellum changed little in fasted or experimentally induced diabetic rats while those in adipose tissues decreased much. The results suggest that insulin-sensitive glucose uptake may occur in some specific cells of the brain but is regulated in a different manner from those in peripheral cells.