COLOCALIZATION OF TIGHT JUNCTION PROTEINS, OCCLUDIN AND ZO-1, AND GLUCOSE-TRANSPORTER GLUT1 IN CELLS OF THE BLOOD-OCULAR BARRIER IN THE MOUSE EYE

The facilitative glucose transporter GLUT1 is abundant in cells of the blood-ocular barrier and serves as a glucose transport mechanism in t he barrier. To see the relationship between the glucose transfer funct ion and junctional proteins in the barrier, we examined the localizati on of GLUT1 and the tight junction proteins, occludin and ZO-1, in the mouse eye. Their localization in the retina, ciliary body, and iris w as visualized by double-immunofluorescence microscopy and immunogold e lectron microscopy. Occludin and ZO-1 were colocalized at tight juncti ons of the cells of the barrier: retinal pigment epithelial cells, non -pigmented epithelial cells of the ciliary body, and endothelial cells of GLUT1-positive blood vessels. Occludin was restricted to these cel ls of the barrier. ZO-1 was found, in addition, in sites not functioni ng as a barrier: the outer limiting membrane in the retina, in the cel l border between pigmented and nonpigmented epithelial cells in the ci liary body, and GLUT1-negative blood vessels. These observations show that localization of occludin is restricted to tight junctions of cell s of the barrier, whereas ZO-1 is more widely distributed.