Acute effects of copper on superoxide dismutase, catalase and lipid peroxidation in the freshwater teleost fish, Esomus danricus

Static-renewal bioassays [Methods for acute toxicity tests with fish, macro-invertebrates and amphibians: USEPA, ERS, EPA 660/3 75-009 (1975)] were carried out on Esomus danricus exposed to sub-lethal (0.55 mg/l) and lethal (5.5 mg/l) concentrations of copper. The 96-h median lethal concentration (LC₅₀) was 5.5 mg/l. Biochemical stress responses, such as visceral superoxide dismutase (SOD) and catalase (CAT) activities, were measured during this 96-h period. Malondialdehyde, a product of lipid peroxidation, was present at elevated levels in the visceral tissue of copper-exposed fish. Copper was found to be highly toxic to the fish and induced significant declines (p < 0.05–0.001) in all of the biochemical profiles studied, demonstrating a linear and positive correlation with both the concentration and duration of exposure to copper. In E. danricus, CAT appeared to be more sensitive to copper exposure (p < 0.001) than SOD at both lethal and sub-lethal levels. These results indicate that antioxidant responses can be employed as biomarkers of oxidative stress for this species in aquatic environments contaminated with copper.