title: Lack of constitutive and inducible ethoxyresorufin-O-deethylase activity in the liver of suckermouth armored catfish (Hypostomus affinis and Hypostomus auroguttatus, Loricariidae).
abstract: We investigated the presence and inducibility of CYP1A in suckermouth catfish (Hypostomus affinis and Hypostomus auroguttatus, Loricariidae), tilapia (Oreochromis niloticus, Cichlidae) and mice (Mus musculus, Muridae). Alkoxyresorufin-O-dealkylases (EROD, MROD, PROD and BROD) were detected and proved to be inducible (beta-naphthoflavone, BNF or dimethylbenz[a]anthracene, DMBA, 50 mg/kg bw ip) in liver microsomes from tilapia and mice. In loricariids, alkoxyresorufin-O-dealkylases were either undetectable (MROD/EROD) or very low (PROD/BROD), and so they remained after treatment with BNF or DMBA. Ethoxycoumarin-O-deethylase (ECOD) was recorded in all species and proved not to be inducible by BNF or DMBA. In loricariids and tilapia, ECOD was not depressed by a concentration of alpha-naphthoflavone (CYP1A-inhibitor) that markedly depressed EROD in tilapia. A CYP1A-like protein was detected by a monoclonal antibody in rats, mice and tilapia, but not in loricariids. A polyclonal antibody, however, detected a CYP1A-like protein in liver microsomes of loricariids. Suckermouth catfish, rats, mice and tilapia express a protein reactive with a polyclonal antibody against trout CYP3A. Loricariids and tilapia exhibited marked genotoxic responses (enhanced incidence of micronucleated erythrocytes) following treatment DMBA (50 mg/kg bw ip), a promutagen activated by CYP1A/1B. Therefore, although not exhibiting EROD, a CYP1A-mediated activity, loricariids converted DMBA into its genotoxic metabolites. Our findings suggest that the CYP1A-like protein of locariid catfish recognizes DMBA, but not ethoxyresorufin, as a substrate.
authors.affiliation: Laboratory of Environmental Toxicology, Department of Biological Sciences, National School of Public Health, Av Brasil 4036 (EXCAM), Rio de Janeiro, RJ 21040-361, Brazil.
authors.forename: T E M
authors.initials: TE
authors.lastname: Parente
authors.forename: A C A X
authors.initials: AC
authors.lastname: De-Oliveira
authors.forename: D G
authors.initials: DG
authors.lastname: Beghini
authors.forename: D A
authors.initials: DA
authors.lastname: Chapeaurouge
authors.forename: J
authors.initials: J
authors.lastname: Perales
authors.forename: F J R
authors.initials: FJ
authors.lastname: Paumgartten
mesh_terms: D015660:7-Alkoxycoumarin O-Dealkylase / Q000378:metabolism; D015127:9,10-Dimethyl-1,2-benzanthracene / Q000378:metabolism / Q000633:toxicity; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D001571:Benzoflavones / Q000494:pharmacology; D002397:Catfishes / Q000378:metabolism*; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D019362:Cytochrome P-450 CYP2B1 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology; D029941:Fish Proteins / Q000096:biosynthesis / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D051379:Mice; D048629:Micronuclei, Chromosome-Defective / Q000139:chemically induced; D008862:Microsomes, Liver / Q000201:enzymology; D009153:Mutagens / Q000378:metabolism / Q000633:toxicity; D010078:Oxazines / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000819:agonists; D013379:Substrate Specificity; D017210:Tilapia / Q000378:metabolism*; D019324:beta-Naphthoflavone / Q000494:pharmacology
chemical_list: D001571:Benzoflavones; D004791:Enzyme Inhibitors; D029941:Fish Proteins; D009153:Mutagens; D010078:Oxazines; D018336:Receptors, Aryl Hydrocarbon; D015127:9,10-Dimethyl-1,2-benzanthracene; C007649:ethoxyresorufin; C011512:alpha-naphthoflavone; D019324:beta-Naphthoflavone; D003577:Cytochrome P-450 Enzyme System; C076307:methoxyresorufin-O-demethylase; D015660:7-Alkoxycoumarin O-Dealkylase; D001189:Aryl Hydrocarbon Hydroxylases; D019363:Cytochrome P-450 CYP1A1; D019362:Cytochrome P-450 CYP2B1; D051544:Cytochrome P-450 CYP3A