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Ascorbate in the corneal epithelium of diurnal and nocturnal species
A Ringvold1, E Anderssen, I Kjønniksen
1Eye Department, National Hospital, University of Oslo, Norway.
Purpose:
To compare the amount of ascorbic acid in the corneal epithelium of various species to unveil possible differences between diurnal and nocturnal mammals.
Methods:
Ascorbic acid was determined by high-performance liquid chromatography, using an LC-10 system (Shimadzu, Kyoto, Japan).
Results:
Diurnal animals show a higher ascorbate concentration in the corneal epithelium than nocturnal animals. Ascorbate concentration is higher in the corneal epithelium than in the matching aqueous humor in diurnal and nocturnal species. The highest ascorbate concentration is found in the corneal epithelium of the reindeer.
Conclusions:
Ascorbate level in the corneal epithelium seems to vary in accordance with ambient radiation exposure of the respective species, just as in the aqueous humor. Both phenomena are regarded as environmental adaptations, and the ascorbic acid is suggested as protecting against photokeratitis and as acting as an ultraviolet filter for internal eye structures.