Excision repair of UVR-induced pyrimidine dimers in corneal DNR

We measured excision repair of ultraviolet radiation (UVR)-induced pyrimidine dimers in DNA of the corneal epithelium of the marsupial, Monodelphis domestica, using damage-specific nucleases from Micrococcus luteus in conjunction with agarose gel electrophoresis. We observed that 100 J m-2 of UVR from a FS-40 sunlamp (280-400 nm) induced an average of 2.2 +- 0.2x 10-2 endonuclease-sensitive sites per kilobase (ESS/kb) (pyrimidine dimers) and that ∼ 50% of the dimers were repaired within 12 h after exposure. We also determined that an exposure of 400 J m-2 was needed to induce comparable numbers of pyrimidine dimers (2.5 x 10-2) in the DNA of skin of M. domestica in vivo. In addition, we found that 50% of the dimers were also removed from the epidermal cells of M. domestica within 12 h after exposure. A dose of 100 J m-2 was necessary to induce similar levels of pyrimidine dimers (2.0 +- 0.2 x 10-2) in the DNA of the cultured marsupial cell line Pt K2 (Potorous tridactylus). (author)