Comparison of plasma ascorbate status between diabetic retinopathy subjects with and without photo-coagulation...

Metabolism of ascorbic acid is deranged in Diabetes Mellitus (DM). One important reason of this derangement is its increased turnover in the process of handling an increased load of free radicals. Anoxia, the triggering factor in the pathogenesis of diabetic retinopathy generates free radicals in anoxia-reperfusion sequence. Any process like argon laser photocoagulation that destroys the anoxic sites and improves oxygenation in retina might hinder the process of generation of free radicals and thus expected to preserve ascorbic acid. In this study plasma total ascorbic acid concentration in matched groups of (I) diabetics with retinopathy with no history of photocoagulation (II) diabetics with retinopathy treated by laser and (III) diabetics without microvascular pathology were measured by 2-4 dinitrophenyl hydrazine method. Plasma total ascorbate concentration was significantly higher in group-II (0.47 +/- 0.09 mg/dl; X +/- SD) in comparison to group-I (0.19 +/- 0.07 mg/dl P < 0.001). The concentration was not significant between group-II and group-III (0.49 +/- 0.06 mg/dl; P = 0.40). Other clinical and metabolic parameters were not significantly different in between the groups. This observation leads to speculation that photocoagulation saves ascorbic acid from excessive turnover in anoxic retina in the process of handling free radicals.