Ascorbate in the corneal epithelium of diurnal and nocturnal species

PURPOSE. To compare the amount of ascorbic acid in the corneal epithelium o f various species to unveil possible differences between diurnal and noctur nal mammals. METHODS. Ascorbic acid was determined by high-performance liquid chromatogr aphy, using an LC-10 system (Shimadzu, Kyoto, Japan). RESULTS. Diurnal animals show a higher ascorbate concentration in the corne al epithelium than nocturnal animals. Ascorbate concentration is higher in the corneal epithelium than in the matching aqueous humor in diurnal and no cturnal species. The highest ascorbate concentration is found in the cornea l epithelium of the reindeer. CONCLUSIONS. Ascorbate level in the corneal epithelium seems to vary in acc ordance with ambient radiation exposure of the respective species, just as in the aqueous hunter. Both phenomena are regarded as environmental adaptat ions, and the ascorbic acid is suggested as protecting against photokeratit is and as acting as an ultraviolet filter for internal eye structures.