Prolonged Marginal Ascorbic Acid Deficiency Induces Oxidative Stress in Retina of Guinea Pigs

We examined whether prolonged marginal ascorbic acid deficiency induces oxidative stress in the retina of guinea pigs. Male guinea pigs aged four weeks were given a scorbutic diet (20 g/animal per day) with either marginally deficient ascorbic acid (0.5 mg/animal per day) or adequate ascorbic acid (1 g/animal per day) in drinking water for three and six months. The retinal contents of the reduced form of ascorbic acid in the deficient group at three and six months were 68.1 and 43.5%, respectively, of that in the corresponding adequate group. The retinal contents of the oxidized form of ascorbic acid in the deficient group at three and six months were 1.9- and 2.7-fold, respectively, higher than that in the corresponding adequate group. The content of retinal thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation, in the deficient group was 2.5-fold higher than that in the adequate group at six months. The retinal contents of reduced glutathione (GSH) in the deficient group at three and six months were 84.8 and 66.7%, respectively, of that in the corresponding adequate group. The deficient group had 37.5% of retinal vitamin E content of the adequate group at six months. The deficient group had higher serum vitamin E concentration than the adequate group in both experimental periods. There were no differences in serum TBARS and GSH concentrations between the groups at both periods. These results indicate that prolonged marginal ascorbic acid deficiency induces oxidative stress in the retina of guinea pigs without systemic oxidative stress.