title: Induced alkoxyresorufin-O-dealkylases in tilapias (Oreochromis niloticus) from Guandu river, Rio de Janeiro, Brazil.
abstract: The activity of fish monooxygenases has been extensively used as a monitoring tool to detect contamination of water bodies by cytochrome P450-inducing agents. In this study we evaluated the activities of ethoxy- (EROD), methoxy- (MROD) and pentoxy- (PROD) resorufin-O-dealkylases in the liver of Nile tilapias (Oreochromis niloticus) collected at the Guandu river, at a reference clean site (Lake 1) and at two other sampling sites (Lakes 2 and 3) in Rio de Janeiro state, Brazil. Alkoxyresorufin-O-dealkylases were measured fluorimetrically in the hepatic S9 fraction. EROD (17.7-fold), MROD (14.2-fold) as well as PROD activities were considerably higher in tilapias from Guandu river. A moderate increase of EROD (5.0-fold) and MROD (5.4-fold) was also found in tilapias from Lake 3. These findings suggest that Guandu river watershed, the main source of urban drinking water supply in Rio de Janeiro, is polluted with CYP1A-inducing xenobiotics. Furthermore, we also found a good linear relationship between EROD and MROD, a finding that agrees with the hypothesis that the two reactions are catalysed by the same CYP1A isoform in O. niloticus.
authors.affiliation: Laboratory of Environmental Toxicology, Department of Biological Sciences, National School of Public Health, Oswaldo Cruz Foundation (FIOCRUZ), Av. Brasil 4325, Rio de Janeiro RJ 21045-900, Brazil.
authors.forename: Thiago E M
authors.initials: TE
authors.lastname: Parente
authors.forename: Ana C A X
authors.initials: AC
authors.lastname: De-Oliveira
authors.forename: Igor B
authors.initials: IB
authors.lastname: Silva
authors.forename: Francisco G
authors.initials: FG
authors.lastname: Araujo
authors.forename: Francisco J R
authors.initials: FJ
authors.lastname: Paumgartten
mesh_terms: D000818:Animals; D001938:Brazil; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism*; D019362:Cytochrome P-450 CYP2B1 / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004784:Environmental Monitoring; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*; D017210:Tilapia / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D014874:Water Pollutants, Chemical; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; C076307:methoxyresorufin-O-demethylase; D019363:Cytochrome P-450 CYP1A1; D019362:Cytochrome P-450 CYP2B1