Formation and persistence of DNA adducts in liver and kidney of brown bullheads exposed to benzo(a)pyrene (BP)

Using the 32P-postlabeling technique, the authors have examined the extent of covalent binding of BP intermediates to DNA of liver and kidney in brown bullheads, the types of DNA adducts formed and the persistence of these adducts. Administration of BP to brown bullheads at a dose of 20 mg/kg (i.p.) resulted in the formation of BP-DNA adducts in both liver and kidney. The formation of the hydrocarbon-DNA adducts in liver proceeded very slowly up to 7 days after treatment. Following this lag, there was a rapid increase in the level of the DNA adducts with the maximum binding noticed 25-30 days after treatment. Subsequently, a substantial decline in the level of BP-DNA adducts occurred. After 42 days of treatment, the total adduct level in liver DNA had decreased to 32% of the maximum adduct level. The general trend for the formation and persistence of BP-DNA adducts in kidney was similar to that noticed with liver except that the maximum DNA adduct formation occurred 12-15 days after treatment and the rate of adduct removal was slower. The predominant adduct (∼ 85%) in both liver and kidney DNA was tentatively identified as BP-7,8-dihydrodiol-9,10-epoxide-deoxyguanosine. In addition, four minor DNA adducts, not yet identified, were detected in both organs. On the basis of these data, liver and kidney, a target and non-target organ, respectively, do not seem to differ significantly from each other with respect to the types and magnitude of BP-DNA adducts formed