ULTRASTRUCTURAL-LOCALIZATION OF GLUT-1 AND GLUT-3 GLUCOSE-TRANSPORTERS IN RAT-BRAIN

Precise localization of glucose transport proteins in the brain has pr oved difficult, especially at the ultrastructural level. This has limi ted further insights into their cellular specificity, subcellular dist ribution, and function. In the present study, preembedding ultrastruct ural immunocytochemistry was used to localize the major brain glucose transporters, GLUTs 1 and 3, in vibratome sections of rat brain. Our r esults support the view that, besides being present in endothelial cel ls of central nervous system (CNS) blood vessels, GLUT 1 is present in astrocytes. GLUT 1 was detected in astrocytic end feet around blood v essels, and in astrocytic cell bodies and processes in both gray and w hite matter. GLUT 3, the neuronal glucose transporter, was located pri marily in pre-and postsynaptic nerve endings and in small neuronal pro cesses. This study: (1) affirms that GLUT 3 is neuron-specific, (2) sh ows that GLUT 1 is not normally expressed in detectable quantities by neurons, (3) suggests that glucose is readily available for synaptic e nergy metabolism based on the high concentration of GLUT 3 in membrane s of synaptic terminals, and (4) demonstrates significant intracellula r and mitochondrial localization of glucose transport proteins. (C) 19 97 Wiley-Liss, Inc.