Formation and persistence of benzo[a]pyrene--DNA adducts in different tissues of C57BL/10 and DBA/2 mice.

Synchronous fluorescence spectrophotometry (SFS) developed to study benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE)--DNA adducts was used to measure the formation and disappearance of DNA adducts in the lung, liver, kidney, spleen and small intestine of genetically responsive C57BL/10 (B10) and nonresponsive DBA/2 (D2) mice. After single stomach intubation of 100 mg/kg of benzo[a]pyrene (B[a]P) in both strains, binding of BPDE to DNA reached a peak 48 h after treatment. However, the levels of binding in the lung, liver, kidney and spleen were higher in D2 than in B10 mice. In contrast to this, in the small intestine the higher level of BPDE binding was found in B10 mice and reached its maximum 24 h earlier. Thereafter a very rapid drop in the level of BPDE--DNA adducts to a value of approximately 50% after 48 h was observed in this tissue. In the other tissues of the B10 mice the rate of adducts removal was slower, but by 14 days after treatment 90-100% of adducts were removed. In the D2 mice up to the 4th day after treatment the rates of removal of the BPDE--DNA adducts were similar to that of the B10 mice. Thereafter the level of bound hydrocarbon decreased at a slower rate. During the whole period after B[a]P treatment distinct differences between organs in the amount of BPDE--DNA adducts were observed. In D2 mice the highest level of binding was found in the spleen followed by the lung, kidney, liver and small intestine. In B10 mice the highest level of binding was observed in the DNA of small intestine. The data suggest that the decreased rate of B[a]P metabolism in D2 mice may be at least in some tissues the reason of higher binding of BPDE--DNA adducts in comparison with B10 mice.