@article {Cui1765, author = {Donghui Cui and Gary O. Rankin and Peter J. Harvison}, title = {TRANSAMINATION IN THE METABOLISM OF THE NEPHROTOXICANT N-(3,5-DICHLOROPHENYL)SUCCINIMIDE IN RATS}, volume = {33}, number = {12}, pages = {1765--1770}, year = {2005}, doi = {10.1124/dmd.105.006593}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) is nephrotoxic in rats. Due to the involvement of NDPS metabolism in its mechanism of toxicity, the detailed biotransformation of 14C-NDPS in rats was previously evaluated using high-performance liquid chromatography-electrospray ionization-mass spectrometry. In the present report, we describe the identification of two novel amino metabolites of NDPS, which were present in significant amounts in rat kidney tissues. Using liquid chromatography-tandem mass spectrometry and synthetic standards, the two metabolites were identified as N-(3,5-dichlorophenyl)-2-aminosuccinamic acid (2-NDASA) and its N-acetylated derivative (N-acetyl-2-NDASA). The mechanism of formation of 2-NDASA was studied in vitro. Incubations were carried out in rat liver and kidney cytosols using the major oxidative metabolite of NDPS, N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid, as the substrate. Formation of 2-NDASA in vitro was confirmed using mass spectrometry. Inhibitors of alcohol dehydrogenase (4-methylpyrazole) and aldehyde dehydrogenase (disulfiram) reduced 2-NDASA formation by 40 to 50\%. Menadione (an inhibitor of aldehyde oxidase) and quercetin (an inhibitor of carbonyl reductase) did not show any effects. (Aminooxy)acetic acid, an inhibitor of pyridoxal 5'-phosphate-containing enzymes such as aminotransferases, almost completely abolished the formation of 2-NDASA. Using liquid chromatography-mass spectrometry, the transamination mechanism was further supported by the incorporation of a 15N-amino group in 2-NDASA when 15N-glutamic acid was included in the incubation mixture. Results from these studies show that transamination is a metabolic pathway in the clearance of NDPS in rats, and that cytosolic dehydrogenases and aminotransferases may be involved in this process. The American Society for Pharmacology and Experimental Therapeutics}, issn = {0090-9556}, URL = {https://dmd.aspetjournals.org/content/33/12/1765}, eprint = {https://dmd.aspetjournals.org/content/33/12/1765.full.pdf}, journal = {Drug Metabolism and Disposition} }