Temperature-induced alterations in the metabolic activation of benzo[ a]pyrene to DNA-binding metabolites in the Bluegill fry cell line BF-2

Abstract

Many carcinogenic chemicals such as the environmental pollutant benzo[ a]pyrene (B[ a]P) require metabolic activation to reactive DNA-binding intermediates in order to induce cancer formation. To determine whether the temperature of incubation affects the proportion of B[ a]P metabolized to DNA-binding metabolites as well as the amount of B[ a]P metabolized, cultures of the Bluegill ( Lepomis macrochirus) fry cell line BF-2 maintained at 23°C and 35°C were exposed to [ 3H]B[ a]P. Exposure at 35°C resulted in an increase in the amount of B[ a]P metabolized by 61% at 24 h compared with cultures incubated at 23°C. The amount of B[ a]P-9,10-diol present in the medium was similar at both temperatures, but the amount of water-soluble metabolites was greater in the cultures maintained at 35°C. The amount of B[ a]P bound to DNA in cultures exposed to B[ a]P at 35°C was 97% greater at 24 h and 61% greater at 48 h than in cultures exposed at 23°C. The increase in the major B[ a]P-deoxyribonucleoside adduct, (+)- anti-B[ a]P-7,8-diol-9,10-epoxide (B[ a]PDE; the isomer with the epoxide and benzylic hydroxyl on opposite faces of the molecule)-deoxyguanosine at 35°C, was 314% and 100% at 24 h and 48 h, respectively. There was no significant change in the amount of syn-B[ a]PDE (the isomer with the epoxide and benzylic hydroxyl on the same face of the molecule)-deoxyguanosine. These results indicate that although the amount of B[ a]P metabolized by BF-2 cell cultures is 60% greater at 35°C than at 23°C, the amount of B[ a]P bound to DNA through the (+)- anti-B[ a]PDE increased by more than 300%. Thus increased temperature can increase the proportion of B[ a]P metabolized to an ultimate carcinogenic metabolite in BF-2 cells in culture.