Direct evidence that an arene oxide is a metabolic intermediate of 2,2′,5,5′-tetrachlorobiphenyl

Radiolabeled arene oxide was recovered from incubations containing [ 3H]-2,2′,5,5′-tetrachlorobiphenyl ( 3H-TCB), unlabeled 2,2′,5,5′-tetrachlorobiphenyl-3,4-oxide (TCBAO), 3,3,3-trichloropropene-1,2-oxide (TCPO), NADPH, and liver microsomes from phenobarbital-induced rats. No labeled arene oxide was generated in the absence of NADPH, nor during the metabolism of unlabeled TCB in the presence of [ 3H]-H 2O. The recovered oxide (radiolabeled and carrier) was characterized by mobility on silica gel and by conversion to 3- and 4-hydroxy-TCB. Formation of a dihydrodiol metabolite was apparently blocked by inhibition of epoxide hydrase. These data provide the first direct evidence that arene oxides are intermediates of halogenated biphenyl metabolism.