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J. Cejkova, T. Ardan, C. Cejka, J. Andonova, Z. Zidek; The Influence of UVA and UVB Rays on Nitric Oxide Generation in the Cornea and Aqueous Humor in Rabbits . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4239.
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Purpose: To examine the role of nitric oxide in the cornea irradiated with UVA or UVB rays. Methods: The rabbit corneas were repeatedly irradiated with UVA or UVB rays (365 nm or 312 nm, 1 x daily for 6 days, the dose per day 1.01 J/cm2). Normal corneas served as controls. After the death of animals, nitric oxide synthase isomers, enzymes generated nitric oxide, nitrotyrosine, a cytotoxic byproduct of nitric oxide, and malondialdehyde, a byproduct of lipid peroxidation, were detected in corneas immunohistochemically. The biochemical determination of nitrite and nitrate has been employed for the indirect investigation of nitric oxide concentration in the aqueous humor. Results: In normal corneas of the nitric oxide synthase isomers only endothelial nitric oxide synthase was significantly stained in the epithelium and endothelium. After the irradiation with UVB rays, endothelial and neuronal nitric oxide synthase and also nitrotyrosine and malondialdehyde stainings were expressed in corneal cells. Inducible nitric oxide synthase, nitrotyrosine and malondialdeyde stainings were highly pronounced in inflammatory cells that invaded the corneal stroma. In the aqueous humor, an elavated concentration of nitric oxide was found. This was in contrast to UVA rays, which evoked only slight increase in stainings of endothelial and neuronal nitric oxide synthases in corneal cells. The level of nitric oxide in the aqueous humor was not significantly increased as compared to normal eyes. Conclusions: The repeated irradiation of the rabbit corneas with UVB rays (not with UVA rays) evoked the stimulation of nitric oxide production, peroxynitrite formation (demonstrated by nitrotyrosine residues) and lipid peroxidation (evaluated by malondialdehyde staining).
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