DNA-REPAIR IN V-79 CELLS TREATED WITH COMBINATIONS OF UV-RADIATION AND N-ACETOXY-2-ACETYLAMINOFLUORENE

Abstract

Earlier experiments in human cells showed that the carcinogen N-acetoxy-2-acetylaminofluorene mimics UV radiation in biological and repair characteristics and the amount of repair from combined treatment was additive. Chinese hamster V-79 [lung] cells are less proficient than human cells in excision repair of pyrimidine dimers resulting from irradiation. The combined effects of both agents on repair in V-79 cells was investigated to see whether they follow the same pattern as in human cells. They did not. Measurements of unscheduled DNA synthesis and the photolysis of DNA repaired in the presence of bromodeoxyuridine gave information about repair due to both agents, and the use of an endonuclease in an extract of Micrococcus luteus allowed measurement of repair of only UV damage in the presence of N-acetoxy-2-acetylaminofluorene damage. Each technique indicated that the amount of repair from combined treatment was less than additive and in some cases less than that due to either agent. V-79 cells are different from human fibroblasts in the excision repair of UV and N-acetoxy-2-acetylaminofluorene damage and both kinds of damages inhibit repair of damage due to the other agent.