title: Transamination in the metabolism of the nephrotoxicant N-(3,5-dichlorophenyl)succinimide in rats.
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.
authors.affiliation: Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences in Philadelphia, 600 South 43 Street, Philadelphia, PA 19104-4495, USA.
authors.forename: Donghui
authors.initials: D
authors.lastname: Cui
authors.forename: Gary O
authors.initials: GO
authors.lastname: Rankin
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Harvison
mesh_terms: D000818:Animals; D005659:Fungicides, Industrial / Q000378:metabolism*; D007668:Kidney / Q000187:drug effects; D008099:Liver / Q000378:metabolism; D008297:Male; D013058:Mass Spectrometry; D051381:Rats; D011916:Rats, Inbred F344; D013388:Succinimides / Q000378:metabolism* / Q000633:toxicity
chemical_list: D005659:Fungicides, Industrial; D013388:Succinimides; C007352:N-(3,5-dichlorophenyl)succinimide