Induction and repair of benzo[a]pyrene-DNA adducts in C57BL/6 and BALB/c mice: association with aging and longevity.

In this study, we employed the sensitive 32P-postlabeling assay to assess the influence of age on the formation and disappearance of benzo[a]pyrene (B[a]P) DNA adducts in six organs of two different mouse strains with different life spans, C57BL/6ByJ (C57BL/6) and BALB/cByJ (BALB/c). Following a single, intraperitoneal treatment with 50 mg B[a]P per kg of bodyweight, maximum formation of the major B[a]P-derived adduct, trans-(7R)-N2-[10-(7 beta,8 alpha, 9 alpha-trihydroxy- 7,8,9,10)-tetrahydrobenzo[a]pyrene]-yl-deoxyguanosine (BPDE-N2-dG), appeared to be age- and organ-dependent; minor differences were observed for the same organs between the two mouse strains. The maximum formation of BPDE-N2-dG in the various organs from young and old mice differed by a factor of 2-4 and was two- to eightfold lower in organs from old mice as compared to young mice. The removal of BPDE-N2-dG, up to 7 days after the treatment, was apparently age- and strain-dependent; non-significant differences were observed for organs within strains at each age studied. In young C57BL/6 mice, which have a greater life expectancy than BALB/c, the rate of disappearance of BPDE-N2-dG was significantly higher in liver and heart as compared to young BALB/c. At the older age a decrease in the rate of BPDE-N2-dG disappearance was observed more frequently, and to a relatively greater extent, in organs from C57BL/6 mice as compared to BALB/c mice. These results are discussed in relation to the differences in life spans and the incidence of pathological lesions between the two strains of mice.