Cadmium Effects on Superoxide Dismutase Activity in Litopenaeus vannamei Hemolymph

Under controlled laboratory conditions the Cd effects on hemolymph superoxide dismutase (SOD) activity were evaluated at 8.8, 24.9 and 249 µg Cd/L and exposure times of 5, 48, and 96 h. Shrimp hemolymph samples were extracted from the first abdominal segment and hemocytes separated by centrifugation, and SOD activity (units/mg of protein in shrimp hemolymph) was quantified using the RANSOD assay kit. No mortality was observed in the controls and treatments. Superoxide dismutase activity ranged from 0.938 ± 0.0938 to 0.946 ± 0.042 SOD units/mg of protein in shrimp hemolymph in controls. At 5-h exposure, SOD activity decreased at all Cd concentrations, with significant differences (p < 0.05) than those of controls. However, a significant (p < 0.05) SOD activity increase was observed at 48-h exposure in those shrimp exposed to 24.9 and 249 µg Cd/L; but a significant (p < 0.05) SOD decrease was determined in those specimens exposed to highest Cd levels at 96-h exposure. More experiments such as those in this study are required for future updates of protection criteria for Cd in estuarine and marine environments.