Turkish Journal of Fisheries and Aquatic Sciences
2014, Vol 14, Num, 1 (Pages: 43-52)
Response of the Antioxidant System of Freshwater Fish (Oreochromis niloticus) Exposed to Metals (Cd, Cu) in Differing Hardness
Dilek Saglam 1 ,Gülüzar Atli 1 ,Zehra Dogan 1 ,Emine Baysoy 1 ,Ceren Gurler 1 ,Ali Eroglu 1 ,Mustafa Canli 1
1 Çukurova University, Faculty of Science and Letters, Department of Biology, 01330, Balcali, Adana, Turkey
DOI :
10.4194/1303-2712-v14_1_06
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Freshwater hardness affects metal toxicity and fish physiology. Therefore, the effects of dissolved metals on fish
physiology may differ in waters from different geographic regions. In this study, toxic effects of Cd and Cu (1 mg/L) on the
antioxidant system of freshwater fish Oreochromis niloticus were investigated in two different waters (commercial and tap
water). Fish were exposed to metals in hard water (320 mg CaCO3/ L, conductivity 5.80 mS/cm) and soft water (80 mg
CaCO3/ L, conductivity 1.77 mS/cm) for 1, 7 and 14 days and consequently the activities of antioxidant enzymes (superoxide
dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX; glutathione reductase, GR and glutathione S-transferase, GST)
and total glutathione (GSH) levels were measured spectrophotometrically. Cu exposure of fish in soft water caused fish
mortality after 8 days, though there was no fish mortality in the other conditions. The antioxidant system of fish responded
differently to metal exposures in waters with differing hardness. Metal exposures in soft water showed predominant effects on
the antioxidant system of fish comparing to hard water exposures. Similarly, antioxidant enzyme activities also altered in
control fish depending on the hardness of waters. In general, CAT was the most sensitive antioxidant enzyme followed by
SOD and GPX. CAT and GSH showed an increasing trend while a decreasing trend was observed for SOD and GPX. This
study emphasized that the water chemistry affects the fish antioxidant system and metal toxicity that may be useful in
environmental monitoring and also evaluating biomarkers in fish from different regions.
Keywords :
Antioxidant enzymes, glutathione, Oreochromis niloticus, hardness, metal