Carcinogen induced DNA damage in isolated rat liver nuclei

Alkali-labile DNA lesions were detected by a hydroxylapatite batch assay following incubation of isolated rat liver nuclei with direct and indirect-acting alkylating agents. N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) (20-200 microM) produced a steep, concentration-related decrease in double stranded DNA. In contrast, only minimal effects on DNA integrity were observed with methylmethane sulfonate (200 microM). The bifunctional alkylating agent, mechlorethamine produced an apparent increase in double-stranded DNA in accord with its ability to induce interstrand DNA crosslinks. The indirect-acting alkylating agent, dimethylnitrosamine (DMN) induced DNA damage only when an NADPH generating system was included in the incubation mixture. These results suggest that isolated rat liver nuclei may be a useful model for studying the effects of mutagenic and carcinogenic chemicals on the integrity of chromosomal DNA.