GLUT2 EXPRESSION IN THE RAT RETINA - LOCALIZATION AT THE APICAL ENDS OF MULLER CELLS

In order to understand the molecular basis of glucose regulation suppo rting visual function, this study examined the presence of GLUT2, a fa cilitated-diffusion glucose transporter isoform, and delineated its lo calization in the rat retina. Reverse transcriptase-polymerase chain r eaction (RT-PCR) demonstrated the presence of GLUT2 mRNA, and immunobl ot analysis using polyclonal antibody specific to rat GLUT2 revealed a band at a molecular weight of approximately 60 kDa, indicating the pr esence of GLUT2 protein in the rat retina. Fluorescence and electron m icroscopy localized GLUT2 expression to the apical ends of Muller cell s that face the inter-photoreceptor space. These findings suggest that GLUT2 on Muller cells may control intra-retinal glucose homeostasis b y performing both anterior and posterior glucose transport within the rat retina. This is the first study to provide evidence that GLUT2 is present in the mammalian central nervous system and indicates that GLU T2 may have local glucose homeostatic functions within the retina in a ddition to its role in the regulation of systemic blood glucose level.