HGD lectures HGD kolokviji 423. kolokvij | 423. kolokvij |
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Grupa za molekularnu biologiju Marta Sofia Sà Ferreira
Organochlorine compounds, such as Polychlorinated Biphenyls (PCBs) and Organochlorine Pesticides like dichlorodiphenyltrichloroethane (DDT), due to their tendency to bioaccumulate and difficult elimination are considered to be toxic, even at low concentrations in the environment. Another group of contaminants frequent in the aquatic environment, the polycyclic aromatic compounds (PAHs), originated from petroleum industry, maritime traffic and combustion; equally promote adverse effects in fish, such as genotoxicity, development alterations and endocrine disruption, among others. This study was conducted with two resident species from River Douro estuary (in the north of Portugal), flounder (Platichthys flesus) a benthonic species, and mullet (Mugil cephalus) a pelagic fish. We have evaluated the accumulation of Persistent Organic Pollutants (POPs), the PCBs, DDT and it stable metabolite the dichlorodiphenyldichloroethylene (DDE), in liver and muscle of both species. In mullet, we have also evaluated the presence of four PAH metabolites in bile, namely phenanthrene, naphthalene, pyrene and benzo(a)pyrene. In environmental monitoring studies it has become frequent the use of several biomarkers. In this study we have evaluated the enzymes from phase I and phase II biotransformation, and oxidative stress, by means of antioxidant enzymes activities and oxidative damages. Both species were allowed to depurate for different periods (1, 4 and 8 months) in a cleaner environment with uncontaminated food, and the levels of pollutants and biomarkers were assessed after depuration periods. Concerning the levels of POPs, no changes were observed in liver even after the 8 month period. However, in muscle a different pattern was seen with a decrease in these pollutants levels after 4 month of depuration. PAH metabolite levels, because they are less lipophilic and more easily metabolised, have significantly decreased with depuration. In flounder, biomarkers responses were conditioned by biological factors, mainly by reproduction, that have limited phase I responses. In addition, the fasting condition during the depuration period, has limited oxidative stress biomarkers at the level of defences and also damages. In mullets, EROD activity has decreased significantly after one month depuration, maintaining the levels throughout the following depuration periods. Phase II biotransformation enzyme in mullet revealed an increase in activity in some periods, however due to the physiological role of this enzyme it can be considered to be beneficial to the animal. Antioxidant enzymes in mullet have equally showed a decrease with depuration, however not so pronounced as phase I decreases. The decrease in oxidative damages in lipids, throughout the depuration, and in proteins after eight months, has confirmed that animals inhabiting Douro estuary are facing oxidative stress induced by the presence of pollutants in the environment. In conclusion, this study revealed the presence of several contaminants in River Douro estuary, and that these compounds induce changes at cellular and subcellular levels in the species inhabiting this aquatic environment. In addition, we can also conclude that mullet can be a useful sentinel species for the presence of several contaminants in European estuaries given their large geographic distribution. Predsjednica HGD-a: Koordinatori predavanja: |
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