Abstract
Abstract: :
Purpose: Vitamin E (VE) is an antioxidant that could inhibit lipid hydroperoxide–induced corneal neovascularization. Recently, the therapeutic effect on severe retinopathy of prematurity is reassessed. Here we studied the effect of VE on oxygen–induced retinal neovascularization in the neonatal rat and its correlation to plasma and retinal VE levels. Methods: Neovascularization was induced by maintaining Sprague–Dawley (SD) neonatal rats in 80% oxygen for 12 days, interrupted daily by 30 minutes in room air, and followed by a progressive return to 80% oxygen. Then the rats were placed in room air until experimental day 18. The rats were treated once daily with oral administration of 1mM Vitamin E in stripped corn oil (1mM VE), 2mM Vitamin E in stripped corn oil (2mM VE), stripped corn oil alone (VE free) or distilled water (DW) at 50µl/10g body weight from day 6 to 17. On day 18, the rats were sacrificed, and the blood and the retinal samples were collected. VE levels in plasma and retinas were measured by HPLC assay. Retinal neovascularization was scored (NV) and avascular areas were measured as a % of total retinal area (%AVA) in ADPase stained retinas. Statistical analysis was performed using Welch's t–test for NV and %AVA. Results: Average plasma VE levels (mean±SD) were 16.59±2.69µl/ml in DW group (n=3), 17.36±4.63µl/ml in VE free group (n=3), 21.25±1.52µl/ml in 1mM VE group (n=3), and 24.83±0.43µl/ml in 2mM VE group (n=3). Average retinal VE levels (mean±SD) were 0.32±0.09µl/mg tissue in DW group (n=3), 0.23±0.09µl/mg tissue in VE free group (n=3), 0.41±0.03µl/mg tissue in 1mM VE group (n=3), and 0.48±0.04µl/mg tissue in 2mM VE group (n=3). Both plasma and retinal VE levels were significantly increased in VE treated animals. The NV scores (mean±SD) were 5.7±0.6 in DW group (n=3), 4.2±3.6 in VE free group (n=7), 3.0±1.9 in 1mM VE group (n=5), and 6.0±1.7 in 2mM VE group (n=6). The NV score in 1mM VE group was significantly lower than those in DW group (p=0.039), but clear differences were not observed between 1mM VE group and VE free group. %AVA (mean±SD) was 37.1±36.9 in DW group, 18.8±22.2 in VE free group, 13.8±14.2 in 1mM VE group, and 20.7±7.0 in 2mM VE group. No significant differences were seen in between each group. Conclusion: This data indicates that Vitamin E in the plasma reaches the retina. Oxygen–induced retinal neovascularization in the neonatal rat was not inhibited by oral administration of 1mM or 2mM Vitamin E.
Keywords: retinal neovascularization • antioxidants • retinopathy of prematurity