Formation and removal of benzo[a]pyrene metabolites--DNA adducts in cultured normal human fibroblasts using a microsome-activating system.

The rate of removal of DNA adducts of several benzo[a]pyrene metabolites from nuclear DNA was compared by introducing a microsome-activating system in human fibroblast cells. Confluent human fibroblasts were exposed to benzo[a]pyrene in the presence of a microsomal activating system and DNA adducts were formed in the nuclear DNA. The adducts present in DNA were determined after 1 h of incubation and 48 h later. There was no difference in the rate of removal between 7S- and 7R -N2-[10-(7 beta, 8 alpha-trihydroxy-7,8,9,10- tetrahydrobenzo[a]pyrene)yl]deoxyguanosine, 7R -N2-[10(7beta, 8 alpha, 9 beta-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene)yl]deoxyguanosine and the covalent adduct of 9-hydroxybenzo[a]pyrene-4,5-epoxide to guanosine. This finding does not agree with the idea that metabolites forming 'persistent DNA adducts' are always responsible for the carcinogenicity of their parent compound.