The metabolism and excretion of mononitrotoluenes by Fischer 344 rats.

The metabolism and excretion of 2-, 3-, and 4-nitrotoluene (2NT, 3NT, and 4NT, respectively) were studied in male Fischer 344 rats. Excreta were collected for 72 hr after an oral dose (200 mg/kg) of radiolabeled 2NT, 3NT, or 4NT. Radiolabel from each NT isomer was rapidly excreted (86, 73 and 74% of the dose for 2NT, 3NT, and 4NT, respectively in 24 hr). The urine was the major route of excretion with 70-85% of the dose being excreted by that route in 72 hr. Five to 13% and 0.0 to 0.1% of the dose was excreted in the feces and expired air, respectively, in 72 hr. The major metabolites excreted in urine in 72 hr after administration of 2NT were 2-nitrobenzoic acid (29% of the dose), an unidentified metabolite (16% of the dose), 2-nitrobenzyl glucuronide (14% of the dose), and S-(2-nitrobenzyl)-N-acetylcysteine (12% of the dose). The major metabolites excreted in urine in 72 hr after administration of 3NT were 3-nitrohippuric acid (24% of the dose), 3-nitrobenzoic acid (21% of the dose), and 3-acetamidobenzoic acid (12% of the dose). The major metabolites excreted in urine in 72 hr after administration of 4NT were 4-nitrobenzoic acid (28% of the dose), 4-acetamidobenzoic acid (27% of the dose), and 4-nitrohippuric acid (13% of the dose). Thus, the major urinary metabolites of 3NT and 4NT differed only quantitatively while those of 2NT were also qualitatively different.