Alterations in the serum biomarkers belonging to different metabolic systems of fish (Oreochromis niloticus) after Cd and Pb exposures.

The serum of vertebrates including human gives sufficient data about the current health status of organism in concern. Biomarkers have gained importance in evaluation of data from biological monitoring studies. In this study, freshwater fish Oreochromis niloticus were individually exposed Cd or Pb using acute (10µM, 2 d) and chronic (20µM, 20 d) exposure protocols to investigate the alterations in serum parameters (ALP, ALT, AST, LDH, lipase, glucose, protein, cholesterol and triglyceride) and response of the endocrine system functioning in different axis, namely HPI (cortisol), HPT (TSH, T3, T4), gonadal (LH, FSH) and prolactin. Data showed that except LH, the levels of all hormones decreased significantly following exposure to Cd and Pb both in acute and chronic exposures. In acute exposures, the activity of ALP and levels of cholesterol and triglyceride decreased significantly following both Cd and Pb exposures, while glucose levels increased only after Cd exposure. In chronic exposures, both metal exposures caused significant decreases in ALP activity and levels of cholesterol and triglyceride, though there were increases in glucose level after Cd exposure and AST, ALT and LDH levels after Pb exposure. Data emphasized the importance of biomarker selection and multiparameter usage of relevant systems in ecotoxicological research to achieve proper evaluation of environmental data.

Response of antioxidant system of tilapia (Oreochromis niloticus) following exposure to chromium and copper in differing hardness.

Tilapias (Oreochromis niloticus) were exposed to copper or chromium in soft water (SW) (~80 mg CaCO3/L, conductivity 1.77 mS/cm) or hard water (HW) (~320 mg CaCO3/L, conductivity 5.80 mS/cm) using 2 exposure protocols (20 µM for 48 h and 10 µM for 144 h). Following the exposures, antioxidant enzyme activities [superoxide dismutase (SOD); catalase (CAT); glutathione peroxidase; glutathione reductase; and glutathione S-transferase (GST)] and glutathione (GSH) levels were measured in the liver of fish. SOD and CAT activities of control fish kept in SW were significantly lower than control fish kept in HW. However, the other antioxidant indices (glutathione metabolism) of both control fish were unaffected from water hardness. Acute metal exposures did not alter the glutathione metabolism, whereas SOD activity in SW and CAT activity in both waters changed significantly. In subchronic duration, Cu exposure caused significant decreases in measured parameters, except for GST activity and GSH level. Similarly, GST activity and GSH level were unaffected from Cr exposure. This study showed that SOD and CAT were the most sensitive antioxidant indices, and that glutathione metabolism, in general, was not altered following metal exposures in different waters.