title: Characterization of microsomal cytochrome P450-dependent monooxygenases in the rat olfactory mucosa.
abstract: Nasal administration of a drug ensures therapeutic action by rapid systemic absorption and/or the entry of some molecules into the brain through different routes. Many recent studies have pointed out the presence of xenobiotic-metabolizing enzymes in rat olfactory mucosa (OM). Nevertheless, very little is known about the precise identity of isoforms of cytochrome P450 (P450)-dependent monooxygenases (P450) and their metabolic function in this tissue. Therefore, we evaluated mRNA expression of 19 P450 isoforms by semiquantitative reverse transcriptase-polymerase chain reaction and measured their microsomal activity toward six model substrates. For purposes of comparison, studies were conducted on OM and the liver. Specific activities toward phenacetin, chlorzoxazone, and dextromethorphan are higher in OM than in the liver; those toward lauric acid and testosterone are similar in both tissues, and that toward tolbutamide is much lower in OM. There are considerable differences between the two tissues with regard to mRNA expression of P450 isoforms. Some isoforms are expressed in OM but not in the liver (CYP1A1, 2G1, 2B21, and 4B1), whereas mRNA of others (CYP2C6, 2C11, 2D2, 3A1, 3A2, and 4A1) is present only in hepatic tissue. Although expression of CYP1A2, 2A1, 2A3, 2B2, 2D1, 2D4, 2E1, 2J4, and 3A9 is noticed in both tissues, there are a number of quantitative differences. On the whole, our results strongly suggest that CYP1A1, 1A2, 2A3, 2E1, 2G1, and 3A9 are among the main functional isoforms present in OM, at least regarding activities toward the six tested substrates. The implication of olfactory P450-dependent monooxygenases in toxicology, pharmacology, and physiology should be further investigated.
authors.affiliation: UMR 1234 Toxicologie Alimentaire, INRA-Université de Bourgogne, Faculté de Pharmacie, 7, boulevard Jeanne d'Arc, BP 87900, 21079 DIJON Cedex, France.
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Minn
authors.forename: Hélène
authors.initials: H
authors.lastname: Pelczar
authors.forename: Claire
authors.initials: C
authors.lastname: Denizot
authors.forename: Michel
authors.initials: M
authors.lastname: Martinet
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Heydel
authors.forename: Bernard
authors.initials: B
authors.lastname: Walther
authors.forename: Alain
authors.initials: A
authors.lastname: Minn
authors.forename: Hervé
authors.initials: H
authors.lastname: Goudonnet
authors.forename: Yves
authors.initials: Y
authors.lastname: Artur
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism; D009831:Olfactory Mucosa / Q000201:enzymology / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D007527:Isoenzymes; D012333:RNA, Messenger; D001189:Aryl Hydrocarbon Hydroxylases