Identification of Urinary Metabolites of Orally Administered N,N-Dimethyl-p-Toluidine in Male F344 Rats∗

∗This manuscript has not been published elsewhere and has not been submitted simultaneously for publication elsewhere.

Abstract

The metabolism of orally administered N,N-dimethyl-p-toluidine (DMPT) in male F344 rats was investigated. The rat urinary metabolite profile was determined by analytical reverse-phase high performance liquid chromatography (HPLC). Four radiolabeled peaks were observed, isolated, and purified by solid-phase extraction (SPE) and preparative HPLC methods. The 4 peaks were identified as p-(N-acetylhydroxyamino)hippuric acid (M1), DMPT N-oxide (M2), N-methyl-p-toluidine (M3), and parent DMPT. Metabolites M1 and M2 were identified by spectrometric and spectroscopic methods, including mass fragmentation pattern identification from both liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry, and from chemical analysis of nuclear magnetic resonance spectra. Structural confirmation of metabolite M2 was accomplished by comparison with a synthetic standard. Peaks M3 and the peak suspected to be DMPT were identified by comparison of their HPLC retention times and mass fragmentation patterns with authentic standards of N-methyl-p-toluidine and DMPT, respectively. DMPT metabolism is similar to that reported for N,N-dimethylaniline.

Keywords:

• N,N-dimethyl-p-toluidine
• metabolism
• glycine conjugate
• N-oxidation
• N-demethylation

ACKNOWLEDGMENTS

This work was supported by Contract Number N01-ES-25483 from the NIEHS. We thank Dr. L.T. Burka at NIEHS for his critical review of the manuscript. We thank Dr. Karen Ann Smith in the Department of Chemistry, University of New Mexico, for her assistance with the NMR experiments. We also thank Mark Gurule, Briana Hedtke-Weber, and Krystal Pacheco of Lovelace Respiratory Research Institute for technical assistance and Ms. Vicki Fisher for assistance with manuscript preparation.

Notes

∗This manuscript has not been published elsewhere and has not been submitted simultaneously for publication elsewhere.