DNA-REPAIR IN XERODERMA PIGMENTOSUM CELLS TREATED WITH COMBINATIONS OF ULTRAVIOLET-RADIATION AND N-ACETOXY-2-ACETYLAMINOFLUORENE

Abstract

Human cells treated with UV radiation, N-acetoxy-2-acetylaminofluorene, and a combination of the 2, were examined for excision repair. The 3 techniques gave similar results. Two types of human cells were used: excision repair proficient (normal human fibroblasts and xeroderma pigmentosum variants); and excision repair deficient (xeroderma pigmentosum C, D and E). Saturation doses were determined and used for combined treatments with both agents. Two patterns of repair were observed: in repair-proficient cells total repair was additive; and in repair-deficient cells total repair was much less than additive (usually less than that observed for separate treatments) and N-acetoxy-2-acetylaminofluorene inhibited excision of pyrimidine dimers. In the 1st group of cells, pathways for repair of UV radiation- and N-acetoxy-2-acetylaminofluorene-induced lesions are not identical and, in the 2nd group of cells, there is an inhibitory effect exerted by major or minor products of each agent on the repair enzyme(s) of the other.