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American Society for Pharmacology and Experimental Therapeutics (ASPET), Drug Metabolism and Disposition, 1(41), p. 79-88, 2012

DOI: 10.1124/dmd.112.048678

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Characterization of Differential Cocaine Metabolism in Mouse and Rat through Metabolomics-Guided Metabolite Profiling

Journal article published in 2012 by Dan Yao, Xiaolei Shi, Lei Wang, Blake A. Gosnell, Chi Chen ORCID
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Rodent animal models, mainly the rat and mouse, have been widely used for studying neurological and toxicological events associated with cocaine abuse. It is known that the mouse is more susceptible to cocaine-induced hepatotoxicity (CIH) than the rat. However, the causes behind this species-dependent sensitivity to cocaine have not been elucidated. In this study, cocaine metabolism in the mouse and rat was characterized through the LC-MS-based metabolomic analysis of urine samples, and were further compared through calculating the relative abundance of individual cocaine metabolites. The results showed that the levels of benzoylecgonine, a major cocaine metabolite from esteratic metabolism, were comparable in the urine from the mice and rats treated with the same dose of cocaine. However, the levels of the cocaine metabolites from oxidative metabolism, such as N-hydroxybenzoylnorecgonine and hydroxybenzoylecgonine, differed dramatically between the two species, indicating species-dependent cocaine metabolism. Subsequent structural analysis through accurate mass analysis and LC-MS/MS fragmentation revealed that N-oxidation reactions, including N-demethylation and N-hydroxylation, are preferred metabolic routes in the mouse, while extensive aryl hydroxylation reactions only occur in the rat. Through stable isotope tracing and in vitro enzyme reactions, a mouse-specific α-glucoside of N-hydroxybenzoylnorecgonine and a group of aryl hydroxy glucuronides high in the rat were identified and structurally elucidated. The differences in the in vivo oxidative metabolism of cocaine between the two rodent species were confirmed by in vitro microsomal incubations. Chemical inhibition of P450 enzymes further revealed that different P450-mediated oxidative reactions in the ecgonine and benzoic acid moieties of cocaine contribute to the species-dependent biotransformation of cocaine.