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Abstract
A dehydroascorbic acid reductase and a glutathione peroxidase have been shown to be present in corneal epithelium. Ascorbic acid (ASC), dehydroascorbate (DHA), or hydrogen peroxide (H2O2) can be coupled to the glutathione reductase system to effect nicotinamide adenine dinucleotide phosphate (NADPH) oxidation. A coupling of the hexosemonophosphate (HMP) shunt via the pyridine nucleotide, NADPH, to DHA has been demonstrated. The suggestion is made that the rate of ASC oxidation in vivo is probably adequate to reoxidize a significant fraction of the NADPH generated by the shunt. ASC, glutathione (GSH), H2O2, and total soluble thiol concentrations of corneal epithelium were determined. At levels of H2O2 within the observed physiological limit, endogenous catalase is inactive.