Cells were cultured from rat livers containing enzyme-altered foci induced by N-2-fluorenylacetamide and the level of DNA repair synthesis in response to several carcinogens was compared in gamma-glutamyl transpeptidase-positive foci cells and in enzyme-negative hepatocytes from the same livers. The level of unscheduled DNA synthesis elicited in foci cells by either the activation-dependent carcinogens N-2-fluorenylacetamide and diethylnitrosamine or the activation-independent carcinogens N-methyl-N'-nitro-N-nitrosoguanidine and 1-methyl-1-nitrosourea was significantly lower than that in hepatocytes. The results suggest that the repair of DNA damage by these altered cells is abnormal.
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