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COCAINE TOXICITY IN FRESHLY ISOLATED RAT HEPATOCYTES – ROLE OF CYP 2B AND CYP 3A

VESSELA VITCHEVA1,2*, MAGDALENA KONDEVA-BURDINA1, RUMYANA SIMEONOVA1, MITKA MITCHEVA1

1.Laboratory of Drug Metabolism and Toxicity; Department of Pharmacology, Pharmacotherapy and Toxicology; Faculty of Pharmacy, Medical University – Sofia, 2, Dunav str., Sofia-1000
2.Center for Food Safety and Nutrition (CFSAN), U.S. FDA, 5100 Paint Branch Parkway, College Park, MD

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Cocaine is a psychoactive compound that undergoes extensive hepatic biotransformation leading to formation of toxic metabolites responsible for its hepatotoxicity. The objectives of this study were to investigate the influence of induction and inhibition on cocaine hepatotoxicity examined in freshly isolated rat hepatocytes. For investigating the role of induction male Wistar rats have been treated in vivo with phenobarbital (75mg/kg, 4 days) and then isolated hepatocytes were exposed to cocaine (50μmol/L for one hour). Compared to control non-treated hepatocytes phenobarbital induction resulted in greater cocaine hepatotoxicity, witnessed by decrease in cell viability by 52%, increase in lactate dehydrogenase (LDH) leakage into the medium by 120%, depletion of reduced gluthathione (GSH) levels by 84% and increase in malondialdehyde (MDA) quantity by 74%. Experimental data in the literature reported two major cytochrome P 450 isoforms CYP 3A and CYP 2B to be involved in cocaine biotransformation and toxicity. In order to trace the relative contribution of these isoforms to cocaine hepatotoxicity in rats, isolated hepatocytes were pre-incubated for 15 min with amiodarone (15μmol/L) and with chloramphenicol (100μmol/L) inhibitors of CYP 3A and CYP 2B, respectively. Pre-incubation with either of the inhibitors ameliorated cocaine hepatotoxicity. Our results prove the role of both isoforms CYP 3A and CYP 2B in cocaine biotransformation in rats.