Effect of high glucose on permeability of retinal capillary endothelium in vitro.

Purpose. To study the effect of high glucose on the permeability of bovine retinal capillary endothelial cell (BRCEC) monolayers. Methods. The paracellular permeability of second-passage BRCEC cultured on millipore filters in two chamber transwell inserts was assayed by measuring the peak trans-monolayer electrical resistance and percent equilibration of 14 C-inulin 48 hours after it had been added to the luminal chamber. Results. High glucose increased the paracellular permeability of BRCEC monolayers independently of its hypertonic action (5 mM glucose: 154.2 ± 21.2 and 19.5 ± 2.4; 30 mM glucose: 134.2 ± 5.1 [P = 0.01] and 23.5 ± 2.I [P = 0.01]; 5 mM glucose ± 25 mM mannitol: 168.7 ± 13.7 ohm . cm 2 [P = 0.04] and 19.3% ± 1.2% 48-hour equilibration of inulin [P = 0.008] ). In a separate series of experiments, the authors were unable to show that either aminoguanidine or ponalrestat prevented the effect of high glucose on permeability (30 mM glucose 95.1 ± 16.7 and 45.4 ± 5.6; 5 mM glucose : 122.9 ± 14.2 [P = 0.02] and 36.6 ± 5.6 [P = 0.001]; 30 mM glucose + aminoguanidine 87.9 ± 17.5 [P =0.4] and 75.3 ± 14.9 [P = 0.6] ; 30 mM glucose + ponalrestat 79.9 ± 12.7 ohm . cm 2 [P = 0.1] and 48.2 ± 2.5% 48-hour equilibration of inulin [P = 0.15]). Ponalrestat did not abrogate the effect of high glucose despite its ability to reduce a high glucose-induced increase in BRCEC intracellular sorbitol levels. Conclusions. The data are consistent with a role for increased paracellular permeability in breakdown of the blood-retinal barrier in diabetic retinopathy, which appears to be independent of both nonenzymatic glycosylation and the polyol pathway.