Developmental expression of GLUT2 in the rat retina

We previously demonstrated that GLUT2, a facilitated-diffusion glucose tran sporter isoform known to play critical roles in the regulation of systemic blood glucose level, is present at the apical ends of Muller cells in the r at retina. As a means of elucidating the ontogeny and possible role(s) of G LUT2 in the developing retina, this study examined its expression at variou s stages of retinal development by immunofluorescence staining using GLUT2- specific antibody. Evidence of GLUT2 expression first appeared at embryonic day 14 (E14) as linear staining along the boundary between the inner and o uter layers of the optic cup, with this staining pattern being present thro ughout subsequent embryonic and neonatal stages. After the development of p hotoreceptor cell inner and outer segments (i.e., photoreceptor layer), GLU T2 immunoreactivity was localized along the boundary between the outer nucl ear layer and photoreceptor layer. Localization of GLUT2 expression and the timing of its appearance, which coincided with the formation of choriocapi llaries, together suggest that GLUT2 is involved in the anterior transport of glucose supplied by choroidal circulation from the early stages of retin al development.