Species- and length of exposure-dependent differences in the benzo(a)pyrene:DNA adducts formed in embryo cell cultures from mice, rats, and hamsters.

The activation of benzo(a)pyrene (BaP) to DNA-binding metabolites in early-passage embryo cell cultures prepared from various species of rodents was investigated by exposing cells from mice (BALB/c and Sencar), rats (Wistar and Fischer 344), and Syrian hamsters to [3H]BaP for various lengths of time. The BaP:DNA adducts containing cis-vicinal hydroxyl groups such as those formed from 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (anti-BaPDE) were separated from the other types of BaP:DNA adducts by immobilized boronate chromatography, and the individual adducts were analyzed by high-performance liquid chromatography. A number of BaP:DNA adducts were present in the DNA from the cultures from all three species after 5 h of BaP treatment. After a 24-h exposure to BaP, the mouse and hamster embryo cell DNA contained a large amount of the adduct formed by reaction of (+)-anti-BaPDE with the 2-amino group of deoxyguanosine (dGuo) and a small amount of a 7 beta,8 alpha-dihydroxy-9 beta,10 beta-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene:dGuo adduct. A large number of BaP:DNA adducts derived from 7 beta, 8 alpha-dihydroxy-9 beta,10 beta-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene and other unidentified BaP metabolites were present in rat embryo cell cultures at all times. Neither the Fischer 344 nor the Wistar rat embryo cell cultures had a significant amount of (+)-anti-BaPDE:dGuo adduct after 5 h of BaP treatment, and in the Wistar rat cells larger amounts of other adducts were present even after a 96-h exposure to BaP. In cell cultures from all three species the proportion of (+)-anti-BaPDE:dGuo adduct increased as the length of time of exposure to BaP increased. There are major differences in the metabolic activation of BaP to DNA binding metabolites in embryo cells from various species of rodents. However, the variations between cell cultures from different strains of rats or mice are not as great as the variations between cell cultures from different species. The time-dependent alterations in the BaP:DNA adducts indicate that analysis after various lengths of time of exposure to BaP is essential to characterize accurately the pathways of metabolic activation of BaP in cells from various species and tissues.