CHARACTERIZATION OF [2-H-3] DEOXY-D-GLUCOSE UPTAKE IN RETINA AND RETINAL-PIGMENT EPITHELIUM OF NORMAL AND DIABETIC RATS

The outer blood-retinal barrier which results from the tight junctions between retinal pigment epithelial cells (RPE) restricts the flow of nutrients reaching the retina. We characterize the transport of [2-H-3 ]deoxy-D-glucose (2-DG) across isolated mammalian neural retina and RP E in terms of their kinetics constants. In addition, the effect of ins ulin on glucose transport was studied by using streptozotocin-induced diabetic rats. RPE accumulates 2-DG by a temperature-sensitive and ene rgy-dependent complex kinetics mechanism. The retina takes up 2-DG by an energy and Na+-dependent saturable system with an apparent K-m of 2 mM. Insulin induced an increase of 2-DG uptake by normal retina. The retina of diabetic rats shows lower levels of 2-DG accumulation. These levels can be returned to the normal ones by exposure to insulin. Alt hough insulin does not affect, significantly, 2-DG accumulation by RPE , 2-DG uptake of RPE from diabetic rats shows a normal saturable kinet ics with an apparent K-m of 20 mM. Those findings suggest the presence of different types of glucose transporters in retina and RPE. Insulin -sensitive glucose transport in retina might be involved in the manife station of diabetic retinopathy.