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Identification of quinone imine containing glutathione conjugates of diclofenac in rat bile.
MedLine Citation:
PMID:  21053927     Owner:  NLM     Status:  In-Process    
High-resolution accurate MS with an LTQ-Orbitrap was used to identify quinone imine metabolites derived from the 5-hydroxy (5-OH) and 4 prime-hydroxy (4'-OH) glutathione conjugates of diclofenac in rat bile. The initial quinone imine metabolites formed by oxidation of diclofenac have been postulated to be reactive intermediates potentially involved in diclofenac-mediated hepatotoxicity; while these metabolites could be formed using in vitro systems, they have never been detected in vivo. This report describes the identification of secondary quinone imine metabolites derived from 5-OH and 4'-OH diclofenac glutathione conjugates in rat bile. To verify the proposed structures, the diclofenac quinone imine GSH conjugate standards were prepared synthetically and enzymatically. The novel metabolite peaks displayed the identical retention times, accurate mass MS/MS spectra, and the fragmentation patterns as the corresponding authentic standards. The formation of these secondary quinone metabolites occurs only under conditions where bile salt homeostasis was experimentally altered. Standard practice in biliary excretion experiments using bile duct-cannulated rats includes infusion of taurocholic acid and/or other bile acids to replace those lost due to continuous collection of bile; for this experiment, the rats received no replacement bile acid infusion. High-resolution accurate mass spectrometry data and comparison with chemically and enzymatically prepared quinone imines of diclofenac glutathione conjugates support the identification of these metabolites. A mechanism for the formation of these reactive quinone imine containing glutathione conjugates of diclofenac is proposed.
Daniel J Waldon; Yohannes Teffera; Adria E Colletti; Jingzhou Liu; Danielle Zurcher; Katrina W Copeland; Zhiyang Zhao
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Chemical research in toxicology     Volume:  23     ISSN:  1520-5010     ISO Abbreviation:  Chem. Res. Toxicol.     Publication Date:  2010 Dec 
Date Detail:
Created Date:  2012-01-03     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8807448     Medline TA:  Chem Res Toxicol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1947-53     Citation Subset:  IM    
Pharmacokinetics and Drug Metabolism and Medicinal Chemistry, Amgen, Inc., 360 Binney Street, Cambridge, Massachusetts 02142, USA.
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