Biochemical changes of antioxidant enzymes in common carp (Cyprinus carpio L.) after heavy metal exposure

Accidental industrial spills may lead to a high concentration of toxic metals in the aquatic environment, as well as affecting freshwater ecosystems with acute and chronic toxicity. Of all aquatic species, fish are particularly sensitive to waterborne contamination and are recognized as bioindicators for water quality monitoring. The objective of the present study was to evaluate the biochemical changes of the enzymatic defense systems in fresh water fish, the common carp (Cyprinus carpio L.), when they are exposed to a heavy metal contaminated aquatic system. The fish were systematically exposed to heavy metal solutions such as cadmium, lead, nickel, and chromium at a sub-lethal level for a period of 32 days. The analytical result indicates that heavy metal toxicity in fish organs gradually increases during the exposure period and slightly decreases at the 32(nd) day. The activity of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione-S-transferase (GST), in the fish were increased. This observation clearly indicates the defensive nature and the adaptive mechanism of cells against free radical induced toxicity. All the results were statistically significant at P < 0.001.