Applied Biology and Biochemistry

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Applied Biology and Biochemistry

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Browsing Applied Biology and Biochemistry by Subject "0. mossambicus"

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    Metal Accumulation and Antioxidant Enzyme Activity in C. gariepinus, Catfish, and 0. mossambicus, Tilapia, Collected from Lower Mguza and Wright Dams, Zimbabwe
    (Springer Science+Business Media, 2009-08-28) Siwela, Andrew H.; Nyathi, C.B.; Naik, Yogeshkumar S.
    The aim of this study was to measure antioxidant enzyme activities as biological indicators of pollution in tissues of two species of fish. Five Clarius gariepinus and three Oreochromis mossambicus were collected from Umguza Dam (polluted dam) whilst seven C. gariepinus and eight 0. mossambicus were collected from Wright Dam (relatively pristine dam). Diphosphotriphoshodiaphorase and catalase activities were consistently lower (42 f 2% and 78 f 20%, respectively) in liver whilst malondialdehyde levels were two times higher in muscles of both species of fish collected from Umguza Dam. However, seleniumdependent glutathione peroxidase (Se-GPX) activity was elevated four-fold in liver and gills of 0. mossambicus collected from Umguza Dam. Metal levels were two to five times higher in muscles of both species of fish collected from Umguza Dam. Fish from Umguza Dam seem to have responded to pollution by increasing Se-GPX specific activity in an effort to detoxify peroxides produced as a result of metal induced oxidative stress. Keywords Antioxidant enzymes . Heavy metals . 0. mossambicus . C. gariepinus High levels of trace metals in freshwater may occur as a result of natural weathering of minerals in the sediments and bed rocks or as a result of anthropogenic activities such as mining, industrial, municipal and agricultural discharges (Winston 1991). Most trace metals are essential in small concentrations for normal metabolic processes in mammals including fish and humans. At abnormally high concentrations, metals can cause death in fish. Metals such as lead (Pb), cadmium (Cd), copper (Cu) mercury (Hg), silver (Hg) and cobalt (Co) have been shown to be extremely toxic when they bind to fish gills (Tao et al. 2000). Fish are exposed to metals through contaminated food and the water column in chronically contaminated aquatic ecosystems, the main routes of accumulation being through gills (Tao et al. 2000). Sublethal and chronic concentration of metals exerts their toxicity on fish by generating free radicals such as the hydroxyl radical ('OH), peroxyl-radical (Roo2) and superoxide (Oo2-) and some non-radical ROS such as hydrogen peroxide (H202). These ROS can trigger oxidative damage to proteins, nucleic acids and lipids (Winston 1991). However, defensive antioxidant enzymes, which detoxify reactive oxygen species, are present in the liver, kidneys, gills and intestine (Buhler and Williams 1988). Antioxidant enzymes have been used as biomarkers of pollution by metals and organic compounds that generate oxidative stress in molluscs (Cossu et al. 2000) whilst MDA levels have also been shown to be affected by oxidative stress (Rodrigues-Ariza et al. 1993). As antioxidant enzyme activities and MDA levels can be used as biomarkers of pollution, this study was undertaken to determine the relat~ onship between concentration of metals, antioxidant enzyme activities and MDA levels in two species of fish collected from Mguza Dam (which receives domestic and industrial effluent from Bulawayo City sewage works) and from Wright Dam with no history of pollution.