Effects of metal (Zn,Cd) and metal mixtures (Zn+Cd) on physiological and biochemical parameters in blood tissues of Oreochromis niloticus

In this study, effects of zinc, cadmium and zinc+cadmium on blood parameters of Oreochromis niloticus were investigated at varying concentrations of metal in the medium and over different periods of time. Fish were exposed to 0.5 and 5.0 mg/L Zn, 0.1 and 1.0 mg/L Cd and 0.5 mg/L Zn+0.1 mg/L Cd and 5.0 mg/L Zn+0.1 mg/L Cd mixtures for 7, 14 and 28 days to observe metal accumulation and physiological and biochemical parameters in blood tissue. Cadmium and zinc accumulation in blood tissue were determined using atomic absorbtion spectrofotometric, serum and blood parameters were measured using spectrophotometric and electrophoretic techniques. No mortality was observed during the experiments. Metal accumulation in blood tissue increased with increasing concentrations of metal in the medium and with increasing exposure periods. Blood tissue accumulation of metals were lower when exposed to the mixture of metals compared with single metal. In O. niloticus, blood and serum parameters were altered by exposure Zn, Cd and Zn+Cd mixtures. Increasing exposure metal concentrations and periods caused a decrease in the levels of RBC, WBC, hematocrit hemoglobin, cholesterol, triglyceride, Ca, Na and Cl and in the ChE activity, and an increase in the activity of CAT, G6PD, ALT, AST, ALP, LDH and LP and in the levels of GSH, serum albumin, transferrin, ceruloplasmine, IgA, IgG, cortisol, glucose, total protein and K. The effects of metals on all blood parameters were always higher in the high concentrations than in the low concentrations and the order of their effects found Zn+Cd>Cd>Zn. Hemoglobin and plasma proteins of O. niloticus were determined by Celulose Acetate Electrophoresis. In all concentrations tested electrophoretic pattern of hemoglobin and plasma proteins consist of 3 and 8 bands, respectively. The 3 bands for hemoglobin (Hb1, Hb2, Hb3) are 2 anodic and 1 cathodic bands. The 8 bands for plasma proteins between 60-94 kDA medium molecular weight proteins (MMWP) for 4 bands and between 120-273 kDA high molecular weight proteins (HMWP) for 4 bands. Plasma protein density of 60, 78 and 94 kDA MMWP bands and 120, 132 and 176 kDA HMWP bands a significant increase were determined. Key Words : Zinc, Cadmium, Oreochromis niloticus, Blood Parameters, Electrophoresis