In vitro activation of 2-aminobenzyl alcohol and 2-amino-6-nitrobenzyl alcohol, metabolites of 2-nitrotoluene and 2,6-dinitrotoluene

: Previous results have suggested that key intermediates in the activation of 2-nitrotoluene and 2,6-dinitrotoluene are 2-aminobenzyl alcohol and 2-amino-6-nitrobenzyl alcohol, respectively. In order to determine the metabolic pathway(s) involved in the activation steps, calf thymus DNA and [14C]-2-aminobenzyl alcohol or [14C]-2-amino-6-nitrobenzyl alcohol were incubated with male Fischer-344 rat hepatic cytosol and PAPS, microsomes and NADPH, or microsomes and cytosol with PAPS, NADPH, and acetyl coenzyme A. DNA was isolated and analyzed for radiolabel bound covalently. Analysis of the incubations containing [14C]-2-aminobenzyl alcohol revealed radiolabel bound covalently to DNA, as well as one major metabolite labile in both sulfatase and acid. The appearance of each required the presence of PAPS and cytosol and was inhibited by the sulfotransferase inhibitor 2,6-dichloro-4-nitrophenol. Neither NADPH nor acetyl coenzyme A played a role in the generation of detectable 14C bound to nucleic acids. 2-Amino-6-nitrobenzyl alcohol was converted to metabolites capable of binding to calf thymus DNA when incubated with cytosol and PAPS or with microsomes and NADPH. However, when cytosol and microsomes were incubated together, activation of 2-amino-6-nitrobenzyl alcohol appeared to require only PAPS, suggesting a minor role for NADPH-dependent enzymes in its activation. The results suggest that the metabolite of 2-nitrotoluene responsible for binding covalently to DNA is 2-aminobenzyl sulfate. There may be more than one pathway involved in the formation of metabolite(s) of 2,6-dinitrotoluene that bind covalently to DNA.