Antioxidant responses and metal accumulation in tissues of Nile tilapia Oreochromis niloticus under Zn, Cd and Zn + Cd exposures

University of Adiyaman, Faculty of Science and Letters, Department of Biology, 02040 Adiyaman, Turkey.
Journal of Applied Toxicology (Impact Factor: 2.98). 05/2009; 29(4):295-301. DOI: 10.1002/jat.1406
Source: PubMed


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.

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    • "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. "
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    • "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. "
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    • "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) "
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