Inhibition of liver microsome-mediated mutagenesis, metabolism and DNA-binding of benzo[a]pyrene and benzo[a]pyrene 7,8-dihydrodiol in the rat following glucose administration

Aroclor 1254-induced rat liver microsomes prepared from control and glucose-treated rats (30% glucose in drinking water 48 h prior to sacrifice) were used in studies of benzo[a]pyrene (BaP) and BaP 7,8-dihydrodiol (BaP 7,8-DHD)-induced mutagenesis in Salmonella typhimurium TA100. Microsome-dependent metabolism and metabolite binding of BaP and BaP 7,8-DHD to calf thymus DNA was also investigated. BaP-induced mutagenesis in TA100 was inhibited 27% and BaP 7,8-DHD-induced mutagenesis was inhibited 55% by microsomes from glucose-treated rats. [³H]BaP and [³H]BaP 7,8-DHD metabolite binding to DNA was inhibited 17% and 20%, respectively. High performance liquid chromatographic (hplc) analysis of enzyme-hydrolyzed DNA yielded 7R and 7S-diol epoxide-1 deoxyguanosine (BPDE-1: dG) adducts and BPDE-2:dG adducts of [³H]BaP and [³H]BaP 7,8-DHD. These adducts were inhibited 38% and 50%, respectively, by microsomes from glucose-treated rats. Hplc analysis of organosoluble metabolites of [³H]BaP and [³H]BaP 7,8-DHD showed an inhibition of metabolism of 28% and 50%, respectively, by microsomes from glucose-treated rats. The inhibition of metabolism correlated with the effect of glucose treatment on inhibition of BaP and BaP 7,8-DHD-induced mutagenesis and adduct formation. These results suggest that the mechanism by which glucose produces its effects on mutagenesis, DNA-binding and adduct formation is by an inhibition of microsome-mediated metabolism of BaP and BaP 7,8-DHD.