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J. Cejkova, T. Ardan, S. Stipek, A. Midelfart; Differences between UVA and UVB rays on Enzymatic Pattern of the Rabbit Cornea . Invest. Ophthalmol. Vis. Sci. 2003;44(13):912.
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Purpose: To examine the effect of UVB or UVA rays on enzymatic pattern of the rabbit cornea.Methods: The corneas of albino rabbits (6 month old) were irradiated with UVB or UVA rays by means of a hand fluorescent lamp (4-Watt) generating 312 nm or 366 nm, from a distance of 0.03m, 5 min exposure, 1 x daily for 5 days. Afterwards the animals were sacrificed and in corneas the activities of gamma-glutamyl transpeptidase, catalase, superoxide dismutase, glutathione peroxidase, xanthine oxidase and some lysosomal hydrolases (acid glycosidases and lysosomal proteases) were examined histochemically, immunohistochemically and biochemically. For the biochemical investigation, scraped corneal epithelium was employed. Normal corneas of albino rabbits served as controls. The damage to the cornea was evaluated histologically. Results: The irradiation of the corneas with UVB rays evoked profound changes of all enzymes studied. In the corneal epithelium (and also in the endothelium) the activities of gamma glutamyl transpeptidase, catalase, superoxide dismutase and glutathione peroxidase were decreased, whereas activities of lysosomal hydrolases were increased, namely in superficial layers of the corneal epithelium. The activity of xanthine oxidase remained high in the corneal epithelium and endothelium. In the superficial layers of the corneal epithelium the xanthine oxidase activity was even increased. In contrast to UVB rays, UVA rays did not evoke significant changes of enzymes in the cornea. Conclusions: The results show that the repeated irradiation of the cornea with UVB rays (known to generate reactive oxygen species) are more dangerous to the cornea than the repeated irradiation with UVA rays. Because the activities of anti-oxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase) are dramatically decreased in the cornea irradiated with UVB rays, it is suggested that this decrease contributes to the danger from oxidative stress to the eye evoked by UVB rays.
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