In vitro binding of 2-acetaminofluorene to RNA and protein with rat liver microsomes

Covalent binding of 2-acetaminofluorene[9-14C] with exogenous Torula yeast RNA and endogenous protein was investigated in liver microsome system in vitro. The binding to protein was 100 times higher than that to RNA. Requirement of NADPH, effectiveness of methylcholanthrene treatment, and inhibition by 7,8-benzoflavone suggest possible involvement of mixed-function oxidases in this binding. The binding was not due to contaminated cytosol in the microsome fraction. Addition of cytosol, sulfate ion, and ATP diminished the binding. Parallel experiments using N-hydroxy-2-acetaminofluorene[9-14C] denied major contribution of this metabolite to the binding of 2-acetaminofluorene in the microsome system. Ring-hydroxylated product was suggested as a possible metabolite for the binding.