title: Induction of hepatic microsomal drug-metabolizing enzymes by inhibitors of 5-lipoxygenase (5-LO): studies in rats and 5-LO knockout mice.
abstract: The effect of 5-lipoxygenase (5-LO) inhibitors on the hepatic microsomal mixed-function oxidase (MFO) system of rodents was investigated. After establishing the relative in vitro and in vivo potencies of the 3 test compounds, male Crl:CD (SD) BR rats received CJ-11,802 (0, 10, 50, or 200 mg/kg/day), zileuton (0, 10, 60, or 300 mg/kg/day) or ZD2138 (0 or 200 mg/kg/day) once daily by oral gavage for 14 (zileuton and ZD2138) or 30 (CJ-11,802) consecutive days. Controls were given an equivalent volume of 0.5% methylcellulose vehicle. At necropsy, all livers were weighed, and sections from representative animals (control and highest dose for each compound) were utilized to prepare hepatic microsomal fractions, which were assayed for cytochrome P-450 (CYP) content and the activities of cytochrome c reductase (CRed), para-nitroanisole O-demethylase (p-NOD), ethoxyresorufin O-deethylase (EROD), and pentoxyresorufin O-dealkylase (PROD). A dose-related increase in liver weight occurred in rats given CJ-11,802 and zileuton, while animals administered ZD2138 were unaffected. Rats given CJ-11,802 (200 mg/kg/day) and zileuton (300 mg/kg/day) had increases in CYP, EROD, PROD, CRed and p-NOD compared to corresponding controls, while only the latter two activities were elevated in animals administered ZD2138. To determine if induction of the hepatic microsomal MFO system was related to 5-LO inhibition, male DBA wild-type and 5-LO knockout mice were administered either CJ-11,802 (200 mg/kg/day) or vehicle by oral gavage for 14 consecutive days. At necropsy, liver weight, CYP content, and CRed activity were measured and all were increased similarly in the treated wild-type and knockout mice compared to corresponding controls, indicating that induction was not related to inhibiting 5-LO.
authors.affiliation: Pfizer Global Research and Development, Drug Safety Evaluation, Eastern Point Road, Groton, Connecticut 06340-8014, USA. william_p_beierschmitt@groton.pfizer.com
authors.forename: W P
authors.initials: WP
authors.lastname: Beierschmitt
authors.forename: J D
authors.initials: JD
authors.lastname: McNeish
authors.forename: R J
authors.initials: RJ
authors.lastname: Griffiths
authors.forename: A
authors.initials: A
authors.lastname: Nagahisa
authors.forename: M
authors.initials: M
authors.lastname: Nakane
authors.forename: D E
authors.initials: DE
authors.lastname: Amacher
mesh_terms: D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000172:deficiency / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction; D006918:Hydroxyurea / Q000031:analogs & derivatives / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000473:pathology; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D018345:Mice, Knockout; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D009245:NADH Dehydrogenase / Q000096:biosynthesis; D009929:Organ Size / Q000187:drug effects; D011714:Pyrans / Q000494:pharmacology; D015363:Quinolones / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D016859:Lipoxygenase Inhibitors; D011714:Pyrans; D015363:Quinolones; C075799:ICI D2138; D003577:Cytochrome P-450 Enzyme System; D001094:Arachidonate 5-Lipoxygenase; D009245:NADH Dehydrogenase; C063449:zileuton; D006918:Hydroxyurea