title: Biomarker responses as indication of contaminant effects in Oreochromis niloticus.
abstract: The current study investigated oxidative stress parameters (enzymes activities, metallothionein content and lipid peroxidation) in freshwater fish, Oreochromis niloticus, tilapia exposure to Monjolinho River (in 4 months of year: January, April, July and November). One critical site in Monjolinho River (site B) was assessed in comparison to a reference site (site A). Water pH and oxygen concentration was lower than that recommended by CONAMA (Brazilian National Environmental Committee), resolution 357/2005 for protection of aquatic communities, and ammonium and the metals Cu, Zn, Mn and Fe (on all months) concentrations were higher than the maximum concentration recommended. Glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities were significantly decreased in liver and muscle in tilapia from Monjolinho River, throughout the year, in relation to reference except in gills that SOD activity increased. Glutathione S-transferase (GST) activity was significantly increased in liver of the tilapia from Monjolinho River in all sites, in relation to reference except in gills that GST activity increased in July and decreased in November, suggesting that GST activity could be induced to neutralize the pollutants toxicity. On the other hand, GST activity was significantly decreased in white muscle indicating a toxic effect of pollutants, resulting in a decreased ability of tilapia to perform defense reactions associated to GSTs. The decrease of catalase (CAT) activity in gills of the O. niloticus together with the increase of SOD activity, could explain the increased lipid peroxidation (LPO) level in this organ. Metallothionein levels in liver and gills were significantly high in all sites. Results indicate that the exposure to metals caused severe damage to tissues; despite the consensually assumed antioxidant induction as a sign of exposure to contaminants the effects seem in part to be mediated by suppression of antioxidant system with SOD, CAT and GPx as potential candidates for tissues toxicity biomarkers of pollutants.
authors.affiliation: Universidade Federal de São Carlos, Campus Sorocaba, Rodovia João Leme dos Santos, km 110, SP-264, CEP 18052-780, Sorocaba, SP, Brazil. san-cleo@ufscar.br
authors.forename: Cleoni dos Santos
authors.initials: Cdos S
authors.lastname: Carvalho
authors.forename: Vanessa Aline
authors.initials: VA
authors.lastname: Bernusso
authors.forename: Heloísa Sobreiro Selistre
authors.initials: HS
authors.lastname: de Araújo
authors.forename: Evaldo Luiz Gaeta
authors.initials: EL
authors.lastname: Espíndola
authors.forename: Marisa Narciso
authors.initials: MN
authors.lastname: Fernandes
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D023681:Cichlids / Q000378:metabolism; D005880:Gills / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D008668:Metallothionein / Q000378:metabolism; D008670:Metals / Q000633:toxicity; D018384:Oxidative Stress / Q000187:drug effects; D013482:Superoxide Dismutase / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D015415:Biomarkers; D008670:Metals; D014874:Water Pollutants, Chemical; D008668:Metallothionein; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005982:Glutathione Transferase