Effects of superoxide generated in vitro on glucuronidation of benzo[a]pyrene metabolites by mouse liver microsomes.

Glucuronidation of benzo[a]pyrene (B[a]P) metabolites, generated in situ by oxidative pathways, was studied using mouse liver uninduced microsomes. No coupling was evident between UDP-glucuronyltransferase and oxygenation of B[a]P. UDPGA protected microsomal macromolecules against binding of reactive B[a]P metabolites. Superoxide, and other reactive oxygen species decreased both the overall B[a]P metabolism and glucuronidation of some B[a]P metabolic products, and caused more extensive binding to macromolecules; UDPGA was less protective in this condition. Peroxidation of microsomes differentially affected glucuronidation of various metabolites of B[a]P, and of various model substrates, indicating that multiple glucuronyltransferases are involved in the conjugation of hydroxylated metabolites of B[a]P.