The long-term objective of this proposal is to determine the biochemical mechanisms by which acute and chronic ethanol exposure influence the N- oxidative metabolism, hepatotoxicity and lethality of cocaine. Ethanol was recently shown to inhibit the carboxylesterase-catalyzed hydrolysis of cocaine to benzoylecgonine and simultaneously cause the same enzyme to catalyze the ethyl transesterification of cocaine to cocaethylene. Unlike benzoylecgonine, cocaethylene is hepatotoxic and may be even more so than cocaine. Like cocaine, cocaethylene can undergo N-demethylation. Thus, the role of cocaethylene and its N-oxidative metabolites in the potentiation of cocaine-induced hepatotoxicity by ethanol will be studied. Cocaethylene also is purported to mediate the increased lethality of cocaine when combined with ethanol. Accordingly, the lethality of cocaethylene and its N-oxidative metabolites also will be examined.
The specific aims of this proposal are: 1. To determine the acute in vivo hepatotoxicity and lethality of cocaine, norcocaine, cocaethylene and norcocaethylene in the mouse as reflected by serum transaminase activity, histological examination and the median lethal dose (LD50). 2. To determine the effects of acute and/or chronic ethanol administration on the in vivo, N-oxidative metabolism and disposition of cocaine and cocaethylene in the rat. 3. To determine the effects of acute and/or chronic ethanol exposure on the in vitro metabolism and cytotoxicity of cocaine, cocaethylene and their N-demethyl derivatives in cultured rat and human hepatocytes. 4. To identify the specific rat and human liver microsomal enzymes responsible for the N-demethylation of cocaine and cocaethylene and N-hydroxylation of norcocaine and norcocaethylene and to characterize the steady-state kinetics, and substrate and inhibitor specificity of these enzymes. Metabolism will be assessed using HPLC and GC/MS methods. Hepatotoxicity and lethality will be studied in intact mice. Cocaine metabolism and disposition will be studied in intact rats. Metabolism and mechanisms of hepatotoxicity also will be studied in cultured hepatocytes. Oxidative metabolism will be studied in microsomal suspensions.
| Dean, R A; Bosron, W F; Zachman, F M et al. (1997) Effects of ethanol on cocaine metabolism and disposition in the rat. NIDA Res Monogr 173:35-47 |
| Kamendulis, L M; Brzezinski, M R; Pindel, E V et al. (1996) Metabolism of cocaine and heroin is catalyzed by the same human liver carboxylesterases. J Pharmacol Exp Ther 279:713-7 |
| Dean, R A; Zhang, J; Brzezinski, M R et al. (1995) Tissue distribution of cocaine methyl esterase and ethyl transferase activities: correlation with carboxylesterase protein. J Pharmacol Exp Ther 275:965-71 |
