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The rodent carcinogen acrylamide (AA) is formed during preparation of starch-containing foods. AA is partly metabolized to the genotoxic epoxide glycidamide (GA). After metabolic processing, the mercapturic acids N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA), rac-N-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA) and rac-N-acetyl-S-(1-carbamoyl-moyl-2-hydroxyethyl)-L-cysteine (iso-GAMA) are excreted with urine. In humans, AAMA can be sulfoxidized to AAMA-sulfoxide. The aim of this study was to assess potential species-differences in AA-toxicokinetics in rats and humans after single oral administration of doses similar to the daily human dietary exposure. Male Fischer 344 rats (n=5/dose group) were administered 20 and 100 μg/kg b.w. 13C3-AA in deionized water via oral gavage. Human subjects (n=3/gender) were orally administered 0.5 and 20 μg/kg b.w. 13C3-AA with drinking water. Urine samples were collected in intervals for 96 and 94 h, respectively. Urinary concentrations of 13C3-AAMA, 13C3-GAMA and 13C3-AAMA-sulfoxide were monitored by liquid chromatography-tandem mass spectrometry. The recovered urinary metabolites accounted for 66.3% and 70.5% of the 20 and 100 μg/kg b.w. doses in rats and for 71.3% and 70.0% of the 0.5 and 20 μg/kg b.w. doses in humans. In rats, 13C3-AAMA accounted for 33.6% and 38.8% of dose and 32.7% and 31.7% of dose was recovered as 13C3-GAMA; 13C3-AAMA-sulfoxide was not detected in rat urine. In humans, 13C3-AAMA, 13C3-GAMA and 13C3-AAMA-sulfoxide accounted for 51.7% and 49.2%, 6.3% and 6.4% and 13.2% and 14.5% of the applied dose, respectively. The obtained results suggest that the extent of AA bioactivation to GA in humans is lower than in rodents.