We investigated the effects of Zn, Cd and a Zn + Cd mixture on antioxidant parameters and metal accumulation in Oreochromis niloticus. Fish were exposed to 0.5 and 5.0 mg l(-1) Zn, 0.1 and 1.0 mg l(-1) Cd, and 0.5 mg l(-1) Zn + 0.1 mg l(-1) Cd and 5.0 mg l(-1) Zn + 1.0 mg l(-1) Cd mixtures for 7 and 28 days to determine Zn and Cd accumulation, reduced glutathione (GSH) level and glucose-6-phosphate dehydrogenase (G6PD) activity in gill and liver. There was increasing accumulation of the metals in the tissues with increasing concentrations of metals in the exposure medium and with increasing duration of exposure (except at the lower concentration of Zn). Concentration of metals in the tissues of fish exposed to the Zn + Cd combination were significantly lower than in fish exposed to the single metal. The highest metal accumulation was observed in the liver. Exposure to the heavy metals affected the antioxidant parameters in the tissues, with both GSH level and G6PD activity in the gill and liver being increased under Zn, Cd and Zn + Cd exposures, especially in their higher concentrations. These increases in the antioxidant responses were higher with the Cd alone, and in combination with Zn, than with Zn alone. Furthermore, GSH level and G6PD activity increased with increasing exposure period only for Cd alone, and in Cd combination with Zn. The results indicate that O. niloticus resisted oxidative stress induced by heavy metal exposure by antioxidant mechanisms.
"Among antioxidant enzymes, SOD is considered as the first line of defence against oxygen toxicity, due to its inhibitory effects on oxyradical formation [58, 59]. The dismutation of the superoxide anion radical is catalyzed by SOD to water and hydrogen peroxide, which afterwards is detoxified by catalase. "
[Show abstract][Hide abstract] ABSTRACT: The evaluation of metal's toxicity in freshwater is one of the imperative areas of research and there is an emergent concern on the development of techniques for detecting toxic effects in aquatic animals. Oxidative stress biomarkers are very useful in assessing the health of aquatic life and more in depth studies are necessary to establish an exact cause effect relationship. Therefore, to study the effectiveness of this approach, a laboratory study was conducted in the fish Labeo rohita as a function of hexavalent chromium and the toxicity indices using a battery of oxidative stress biomarkers such as catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GR) in the liver, muscle, gills, and brain have been studied along with biometric parameters, behavioral changes, and Cr bioaccumulation. A significant increased HSI was observed in contrast to CF which reduced significantly. SOD, CAT, and GR activity increased significantly in all the tissues of treated fishes. The bioaccumulation of Cr was highest in liver followed by gills, muscle, and brain. This study highlights the significance of using a set of integrated biomarker and advocate to include these parameters in National Water Quality Monitoring Program in areas potentially polluted with metals to assess the health of the ecosystem.
BioMed Research International 09/2014; 2014:782493. DOI:10.1155/2014/782493 · 2.71 Impact Factor
"Although zinc is an important trace element in fish nutrition, excessive waterborne zinc can have severe impacts on fish species, causing morphological alterations in the gills, osmoregulatory disturbances and liver damage (Van Dyk et al., 2007; Giardina et al., 2009; McGeer et al., 2000). Many studies had earlier been conducted to explore the effect of zinc exposure on the antioxidant defense system in a variety of fish (Atli and Canli, 2010; Hansen et al., 2007; Firat et al., 2009; Zheng et al., 2011). Nevertheless, response to zinc-mediated oxidative stress in environmentally relevant situations is still a relatively blank field which needs special attention since environmental factors can have a considerable effect on the toxicity of zinc. "
[Show abstract][Hide abstract] ABSTRACT: In this study, laboratory experiments were conducted to investigate the combined effect of zinc and pH on metal accumulation and oxidative stress biomarkers in Carassius auratus. Fish were exposed to 0.1 and 1.0mg Zn/L at three pH values (5.0, 7.25, 9.0) for 3, 12, and 30d. After each exposure, the contents of three trace elements (Zn, Fe and Cu) were determined in liver. Generally, longer exposure to zinc (12d and 30d) increased hepatic Zn and Cu deposition, but decreased Fe content. Increasing accumulation of Zn in the tissue was also observed with increasing zinc concentration in the exposure medium. Moreover, hepatic antioxidant enzyme activities including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), together with the level of glutathione (GSH) were measured to evaluate the oxidative stress status. The decreases in the four measured biochemical parameters after 3d exposure might reflect the failure of the antioxidant defense system in neutralizing the ROS generated during the metabolic process, while the recovery of the antioxidants at days 12 and 30 suggested a possible shift toward a detoxification mechanism. With regard to the influence of pH on zinc toxicity, the general observation was that the living environment became more stressful when the water conditions changed from an acidic state toward a near-neutral or alkaline state.
"0.32, 0.64, and 1.27 mg/l 14 days O. niloticus + Atli and Canli (2008) Zn, Cu, Cd, As, Pb Field studies C. gariepinus + Farombi et al. (2007) Cd, Pb 10, 20, 40, 80, and 160 μg/l 30 days M. cephalus − Rajkumar and Milton (2011) Hg 35, 70, and 140 μg/l 10 days I. melas − Elia et al. (2003) Zn, Cd, Cd+Zn, Zn+Cd 0.5, 5; 0.1, 1; 0.5+0.1; and 5+1 mg/l 7 and 28 days O. niloticus + Firat et al. (2009) Cd, Cr+TA, LA, CUR , NAC 5, 7.5 mg/kg, 50 mg/kg 96 h C. carpio carpio L. + Karaytug et al. (2011) Cr, +ß-NF 5.2, 0.05 mg/l+0.73 mg/l 24 h A. anguilla − Ahmad et al. (2006) Cd 0–8 mg/l 28 days P. olivaceus − Cao et al. (2012) Cu, Mn 0.005, 0.050; 0.17, 1.7 mg/l 14 days C. auratus − Falfushynska et al. (2011) Hg 48.1, 99.4 μg/l 48 h P. olivaceus + Huang et al. (2010) Cd 6.7, 13.4, and 20.1 mg/l 96 h C. punctatus + Dabas et al. (2012) GSSG Ag ions 0.5, 1 μg/l 7 days P. reticulate + Zitka et al. (2010) Cd, Cr+TA, LA, CUR , NAC 5, 7.5, and 50 mg/kg 96 h C. carpio carpio L. + Karaytug et al. (2011) "
[Show abstract][Hide abstract] ABSTRACT: Toxic metals and metalloid are being rapidly added from multiple pathways to aquatic ecosystem and causing severe threats to inhabiting fauna including fish. Being common in all the type of aquatic ecosystems such as freshwater, marine and brackish water fish are the first to get prone to toxic metals and metalloids. In addition to a number of physiological/biochemical alterations, toxic metals and metalloids cause enhanced generation of varied reactive oxygen species (ROS) ultimately leading to a situation called oxidative stress. However, as an important component of antioxidant defence system in fish, the tripeptide glutathione (GSH) directly or indirectly regulates the scavenging of ROS and their reaction products. Additionally, several other GSH-associated enzymes such as GSH reductase (GR, EC 22.214.171.124), GSH peroxidase (EC 126.96.36.199), and GSH sulfotransferase (glutathione-S-transferase (GST), EC 188.8.131.52) cumulatively protect fish against ROS and their reaction products accrued anomalies under toxic metals and metalloids stress conditions. The current review highlights recent research findings on the modulation of GSH, its redox couple (reduced glutathione/oxidised glutathione), and other GSH-related enzymes (GR, glutathione peroxidase, GST) involved in the detoxification of harmful ROS and their reaction products in toxic metals and metalloids-exposed fish.
Environmental Science and Pollution Research 01/2013; 20(4). DOI:10.1007/s11356-012-1459-y · 2.83 Impact Factor
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