Activity of the enzymes of the antioxidative system in cadmium-treated Oxya chinensis (Orthoptera Acridoidae)

One purpose in this research was to determine the toxic effects of Cd on antioxidant enzymes of Oxya chinensis (Orthoptera: Acridoidae). Changes in the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and guaiacol peroxidase (GPx) were measured in O. chinensis insects injected with Cd2+. Fifth-nymphs of O. chinensis insects were injected with Cd2+ at different concentrations (0, 0.55 × 10−4, 1.10 × 10−4, 1.65 × 10−4, 2.20 × 10−4, and 2.75 × 10−4 g g−1). An increase in SOD activity in O. chinensis was observed at 1.10 × 10−4 to 2.75 × 10−4 g g−1 Cd2+. The SOD activity was lower at 2.20 × 10−4and 2.75 × 10−4 g g−1 than that at 1.10 × 10−4 and 1.65 × 10−4 g g−1. It appears that SOD had a positive protective effect at low Cd2+ concentrations, and that this effect disappeared at high Cd2+ concentrations. CAT activity was accelerated to varying degrees at 1.10 × 10−4 to 2.75 × 10−4 g g−1 for males and at 1.10 × 10−4, 2.20 × 10−4, and 2.75 × 10−4g g−1 for females. CAT showed a strong detoxification effect with all treatments. GPx activity decreased with increasing Cd2+ concentration with all treatments for males and at 2.20 × 10−4 and 2.65 × 10−4g g−1 for females. We showed that GPx activity had a weak detoxification function with all treatments for males and at high Cd2+ for females. Thus, CAT had a strong detoxification effect, whereas SOD had a medium and GPx had a weak detoxification effect. Among the three enzymes, CAT played an important role in the damaging mechanisms of reactive oxygen species in O. chinensis insects. Alterations of the antioxidant enzyme level under environmental stresses are suggested as indicators of biotic and abiotic stress.