In vivo and in vitro metabolism of 2,4-dinitrotoluene in strain A mice.

The elimination and metabolism of a single dose (100 mg/kg) of 2,4-dinitrotoluene (2,4-DNT) in A/J mice were examined. After intraperitoneal administration, elimination was rapid, with 70% of the dose appearing in the urine within 4 hr. Four hours after oral administration, only 28.5% of the dose was excreted in the urine, which increased to 66% after 8 hr. Elimination via the feces was minimal (less than 2.1% of the dose) in both cases. From 0.5 to 4 hr after intraperitoneal administration, 3.6 to 8.8% of the urinary metabolites was unconjugated while 2.4 to 8.8% was present in the glucuronide fraction. After oral administration these amounts were 5.5 to 6.8% and 20.5 to 28.2% respectively. After both intraperitoneal and oral administration, no unchanged 2,4-DNT could be detected in the urine, and 2,4-dinitrobenzyl alcohol (2,4-DNBAlc) represented the most abundant identifiable neutral metabolite. Small amounts of 2,4-diaminotoluene, 2-amino-4-nitrobenzyl alcohol, 2-(N-acetyl)amino-4-nitrotoluene, 4-amino-2-nitrotoluene (4A2NT), and 2-amino-4-nitrotoluene (2A4NT) were also present. In almost all cases the largest proportion of metabolites represented unknowns, some of which exhibited the chromatographic properties of carboxylic acid metabolites. Metabolism of 2,4-DNT by liver and lung microsomes yielded mainly 2,4-DNBAlc with lower amounts of 4A2NT and 2A4NT, and their formation was dependent on the presence of oxygen and NADPH. Pretreatment of the animals with 2,3,7,8-tetrachlorodibenzo-p-dioxin resulted in increased yields of all three metabolites. Aerobic metabolism of 2,4-DNT by explants of the small intestine, large intestine, or by cecal contents yielded 2,4-DNBAlc, 2A4NT, 4A2NT and 4-(N-acetyl)amino-2-nitrotoluene (4Ac2NT). The proportion of reduced metabolites (2A4NT, 4A2NT, and 4Ac2NT) was much higher in these systems than with liver or lung microsomes and their formation by small intestine and cecal contents was enhanced several-fold under anaerobic conditions, while that of 2,4-DNBAlc was abolished. It is concluded that 2,4-DNT metabolism in the A/J mouse is rapid and complete and that the major neutral urinary metabolite is 2,4-DNBAlc. Minor amounts of reduced or partially reduced products appear to be formed mainly in the intestine, with a major role by its microflora.