Assessment of chromium toxicity in Cyprinus carpio through hematological and biochemical blood markers

Static renewal exposure of various sublethal concentrations of hexavalent chromium [Cr(VI)] produced a deleterious effect on some hematological and biochemical parameters of Cyprinus carpio with the increase in concentration of metal. C. carpio breeders (W = 500 +/- 9.5 g; L = 25.60 +/- 2.6 cm) were randomly divided into the control group (n = 33) and treated group (n = 198), with 11 breeders/tank (8.84 m3). The groups were distributed into tanks containing 1 of 7 sublethal concentrations of Cr(VI) (0, 25, 50, 75, 100, 125, and 150 mg/L), with 3 replicates per concentration for 6 months. Monthly Cr(VI) levels in the water were determined with an atomic absorption spectrophotometer. The Cr(VI) induced a significant increase (P < 0.05) in white blood cells, mean corpuscular volume, erythrocyte sedimentation rate, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and acid phosphatase, indicating anemia. However, red blood cells, hemoglobin, packed cell volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, glucose, protein, and cholesterol decreased significantly (P < 0.05) with the increase in Cr(VI) concentrations from 25 to 150 mg/L. The actual Cr(VI) concentration varied from 36 to 118 mu g/L in the tanks exposed to concentrations from 25 to 150 mg/L. The increasing trend was probably due to the toxic effects of the Cr(VI) and activation of the fish immune system to resist against metallic stress and liver damage. The decreasing trend reflected retarded and deteriorated fish health along with severe hemolysis.