NITRITE-INDUCED PHOTOOXIDATION OF THIOL AND ITS IMPLICATIONS IN SMOG TOXICITY TO THE EYE - PREVENTION BY ASCORBATE

Studies have been conducted on nitrite-induced oxidation of corneal th iols and reduced glutathione (GSH). Oxidation of GSH in the presence o f nitrite (NaNO2) was minimal in the dark. Exposure of GSH to UV (365 nm) in the presence of nitrite substantially accelerated this oxidatio n; only <10% of the original GSH remained at the end of 20 minutes. A similar Thiol depletion was observed in the case of corneal epithelial extracts irradiated with UV in the presence of the nitrite. Nitrite i s therefore considered to be a potent phototoxicant with possible path ophysiological implications to the external eye tissues. Ascorbate was found to be effective in preventing thiol oxidation, suggesting the p ossibility of preventing nitrogen oxide-based smog irritation to the e ye by this physiologically compatible antioxidant.