title: Induction of rat hepatic cytochrome P-450 by ketamine and its toxicological implications.
abstract: Ketamine is a common intravenous anesthetic and a frequent drug of abuse, alone or in combination with cocaine. However, the pharmacokinetic effects of ketamine have not been fully investigated. This study determined the effects of ketamine on cytochrome P-450 (P-450)-dependent catalytic activities, protein levels, and hepatotoxicity using male Wistar rats treated with 10, 20, 40, or 80 mg/kg ketamine intraperitoneally twice daily for 4 d. Treatment with ketamine produced a dose-dependent increase of pentoxyresorufin O-dealkylation activity of liver microsomes. Treatment with 80 mg/kg ketamine resulted in 14-, 3-, and 2-fold rise in O-dealkylation of pentoxyresorufin, ethoxyresorufin, and methoxyresorufin of rat liver microsomes, respectively. The treatment produced 31% and 86% increases in 7-ethoxycoumarin O-deethylation and erythromycin N-demethylation, respectively. In addition, aniline hydroxylation activity was elevated by 62%. Protein blot analysis of liver microsomal proteins revealed that 80 mg/kg ketamine induced P-450 1A, 2B, 2E1, and 3A proteins by 2-, 13-, 2-, and 2-fold, respectively. In reversibility study, ketamine-induced pentoxyresorufin O-dealkylation, 7-ethoxycoumarin O-deethylation, erythromycin N-demethylation, and methoxyresorufin O-demethylation activities of liver microsomes prepared from rats 4 d after ketamine treatment were 75%, 48%, 29%, and 38% lower than the respective activities of liver microsomes prepared from rats 1 d after treatment. Protein blot analysis showed that ketamine-induced P-450 2B1/2 proteins also decreased in a time-dependent manner in 4 d. In hepatotoxicity study, treatment of rats with 1 ml/kg CCl4 produced a 7-fold increase in serum alanine aminotransferase activity level and a 17-fold rise in rats pretreated with 80 mg/kg ketamine for 4 d. Treatment of ICR mice with 120 mg/kg cocaine produced a 17% mortality, whereas the same dose of cocaine produced a 50% mortality in mice pretreated with ketamine. Treatment of mice with 100 mg/kg cocaine produced a 76-fold increase in serum alanine aminotransferase activity level and a 260-fold rise in mice pretreated with 80 mg/kg ketamine for 4 d. The present study shows that ketamine induces the expression of multiple forms of P-450 in rat liver microsomes and increases CCl4-induced liver toxicity and cocaine-mediated acute toxicity. Other potential pharmacological or toxicological events related to ketamine use need to be further explored.
authors.affiliation: Institute of Toxicology, National Taiwan University, Taipei, Taiwan.
authors.forename: Wei-Hung
authors.initials: WH
authors.lastname: Chan
authors.forename: Wei-Zen
authors.initials: WZ
authors.lastname: Sun
authors.forename: Tzuu-Huei
authors.initials: TH
authors.lastname: Ueng
mesh_terms: D000778:Anesthetics, Dissociative / Q000633:toxicity*; D000818:Animals; D002251:Carbon Tetrachloride / Q000008:administration & dosage; D003042:Cocaine / Q000008:administration & dosage; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D015786:Cytochromes b5 / Q000096:biosynthesis; D004357:Drug Synergism; D007649:Ketamine / Q000008:administration & dosage / Q000633:toxicity*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D009026:Mortality; D009251:NADPH-Ferrihemoprotein Reductase / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D015431:Weight Loss
chemical_list: D000778:Anesthetics, Dissociative; D007649:Ketamine; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System; D002251:Carbon Tetrachloride; D009251:NADPH-Ferrihemoprotein Reductase; D003042:Cocaine