DNA damage is involved in the induction of opacification and neovascularization of the cornea by ultraviolet radiation.
Studies were conducted to examine ultraviolet radiation (UVR)-induced alterations of the cornea of the gray, short-tailed opossum. Monodelphis domestica, and the effect of post-UVR illumination to photoreactivation light (PRL, 320-500 nm). As photoreactivation treatment specifically monomerizes pyrimidine dimers, an amelioration of the UVR-induced biological end-point would implicate DNA as being a primary chromophore for induction of that end-point. Corneas of anesthetized, four-month-old, opossums were exposed to 250 J m-2 (0.025 J cm-2) from a Westinghouse FS20 sunlamp either one or three times a week for up to 13 exposures. The corneas of 4-5 animals received either: (a) 90 min of PRL immediately prior to UVR; (b) PRL immediately following UVR; (c) PRL alone; or (d) UVR alone. Eyes were examined with a slit lamp microscope 24 hr following each exposure and scored for the appearance of opacification and neovascularization of the cornea. In animals exposed to UVR alone, 2-5 exposures, depending on whether the exposures were given once or three times per week, were required to obtain opacification and neovascularization in 50% of the irradiated corneas. The onset of both opacification and neovascularization in 50% of the corneas required 8-11 exposures when the UVR was immediately followed by PRL. Based on the specificity of photoreactivation repair to act solely on pyrimidine dimers, these observations suggest that UVR-induced pyrimidine dimers in corneal DNA are involved in UVR-induced opacification and neovascularization of the cornea of Monodelphis domestica.
Applegate
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LA
Center for Photomedicine, Lovelace Medical Foundation, Albuquerque, NM 87108.
Ley
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RD
D000818:Animals; D003315:Cornea / Q000098:blood supply / Q000528:radiation effects*; D003318:Corneal Opacity / Q000209:etiology / Q000235:genetics*; D004249:DNA Damage / Q000502:physiology*; D008027:Light / Q000009:adverse effects; D009389:Neovascularization, Pathologic / Q000503:physiopathology*; D009893:Opossums; D014466:Ultraviolet Rays / Q000009:adverse effects*