title: Differences in hepatic cytochrome P450 activity correlate with the strain-specific biotransformation of medetomidine in AX/JU and IIIVO/JU inbred rabbits.
abstract: Medetomidine is an alpha(2)-adrenoceptor agonist with sedative and analgesic properties. Previously we demonstrated significant differences in the response to medetomidine between two inbred rabbit strains, denoted IIIVO/JU and AX/JU. The aim of the present study was twofold: first, to compare the hepatic CYP450 enzyme activities between these rabbit strains [n = 13(male male,7 female female)/strain]. To this end, liver microsomes were incubated with known fluorescent substrates for the major drug-metabolizing CYP450 isoforms. A comparison of the obtained results indicated significant gender differences as well as differences between the two rabbit inbred strains. Secondly, the biotransformation rate of medetomidine in liver microsomes of both rabbit strains was determined using liquid chromatography coupled to tandem mass spectrometry. The rate of hydroxymedetomidine and medetomidine carboxylic acid formation was found to be significantly higher in the AX/JU strain. Specific CYP2D and CYP2E inhibitors could decrease the formation of both metabolites. Significant correlations were found between the rate of biotransformation of medetomidine and the activities of CYP2D and CYP2E, as well as between CYP450 enzyme activities and the anaesthetic response to medetomidine.
authors.affiliation: Central Laboratory Animal Institute, Utrecht University, Utrecht, The Netherlands. h.avsaroglu@gdl.uu.nl
authors.forename: H
authors.initials: H
authors.lastname: Avsaroglu
authors.forename: S
authors.initials: S
authors.lastname: Bull
authors.forename: R F
authors.initials: RF
authors.lastname: Maas-Bakker
authors.forename: P
authors.initials: P
authors.lastname: Scherpenisse
authors.forename: H A
authors.initials: HA
authors.lastname: Van Lith
authors.forename: A A
authors.initials: AA
authors.lastname: Bergwerff
authors.forename: L J
authors.initials: LJ
authors.lastname: Hellebrekers
authors.forename: L F M
authors.initials: LF
authors.lastname: Van Zutphen
authors.forename: J
authors.initials: J
authors.lastname: Fink-Gremmels
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D001711:Biotransformation; D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism; D008297:Male; D020926:Medetomidine / Q000494:pharmacology*; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology*; D011817:Rabbits; D013045:Species Specificity; D013379:Substrate Specificity
chemical_list: D000316:Adrenergic alpha-Agonists; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D003577:Cytochrome P-450 Enzyme System; D020926:Medetomidine