Erythrocyte/HepG2-type glucose transporter is concentrated in cells of blood-tissue barriers

In search of possible diverse roles of glucose transporters (GT's), we examined whether any GT's are present in blood-tissue barriers where selective flow of glucose from blood to tissue cells is critically important. We found in rat that the erythrocyte/HepG2-type GT is localized in all the limiting plasma membranes known to serve as blood-tissue barriers, whether the barriers are endothelial type (brain, iris, inner retina, peripheral nerve) or epithelial type (choroid plexus, ciliary body, outer retina, peripheral nerve, placenta), except for plasma membranes in testis and thymus where no appreciable amount of the GT was found. The erythrocyte/HepG2-type GT may play a vital role for the entry of glucose into these firmly guarded tissues.