title: Selective excision of gamma ray damaged thymine from the DNA of cultured mammalian cells.
abstract: Three mammalian cell lines (WI-38, SV40-transformed WI-38 and Chinese hamster ovary) were exposed to high doses of 137-Cs gamma rays and their DNA analysed, following various periods of postirradiation incubation, for products of the 5,6-dihydroxy-dihydrothymine type. Within fifteen minutes of incubation at 37 degrees C 70 to 90 percent of these radiation products were removed from acid-precipitable material in all three cell lines. The amount of DNA degradation induced by radiation varied from approximately one percent in WI-38 cells to 15 percent in SV40-transformed WI-38 cells. Comparison of DNA degradation with the amount of thymine radiation product removed indicates that a selective gamma ray-induced excision repair capability exists in mammalian cells. Because of its more rapid kinetics, gamma ray excision repair is probably a distinct process as compared with ultraviolet-induced pyrimidine dimer excision.
mesh_terms: D000818:Animals; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D006224:Cricetinae; D004247:DNA / Q000378:metabolism / Q000528:radiation effects*; D005260:Female; D008168:Lung / Q000196:embryology; D010053:Ovary; D011830:Radiation Effects; D013539:Simian virus 40; D013941:Thymine / Q000378:metabolism / Q000528:radiation effects*; D013997:Time Factors
chemical_list: D004247:DNA; D013941:Thymine