Oxidative Stress And DNA Damage Induced By Imidacloprid And Thiamethoxam Exposure In Zebra-fish (Danio Rerio)

Neonicotinoid insecticides are the kind of important of insecticides after Carbamate, Organophosphates, parathyroid insecticides. Imidacloprid and thiamethoxam, respectively is the first generation and second generation representative of the neonicotinoid insecticides. Imidacloprid is one of the fastest domestic growing new nokia methyl nitrate class of pesticides in recent years, mainly used for prevention and control delphacidae, whitefly, aphids and other sucking mouthparts pests. Imidacloprid has been favored by the global international market since1991on the market because of its high efficiency, broad-spectrum, low toxicity to mammals, and good stability in the field and other characteristics. Thiamethoxam, its different structure with imidacloprid, lead to higher activities of the sucking mouthparts pests and some lepidoptera pests. It not only has tough out, stomach poison, inside absorb activity, but also has higher activity, better security and the broader insecticidal spectrum and fast, the effective length and other characteristics, saling volume after imidacloprid in new neonicotinoid insecticide at present. The extensive use of imidacloprid and thiamethxam will both cause ecological toxicity to non-target organisms. This article selects the international recognized the biological model animal-zebra fish (Danio rerio) as a biological indicator, and this study was conducted to investigate the effect of imidacloprid and thiamethoxam on antioxidant enzymes [catalase (CAT) and superoxide dismutase (SOD)], ROS (Reactive Oxygen Species) generation, GST and DNA damage in zebra fish. Zebra fish were exposed to a control solution and three concentrations of imidacloprid and thiamethoxam (0.3,1.25, and5mg/L) and both were sampled after7,14,21, and28days. And then evaluate their oxidative stress and genetic toxicity to zebra fish to comprehensively recognize and understand imidacloprid and thiamethoxam to provide the basis of their potential influence of aquatic ecological system. In conclusion, this study proved imidacloprid and thiamethoxam (0.3-5mg/L) has obvious toxicity in zebra fish. They have activation or inhibition effect on determination indexes. The main results are showed as follows:(1) Antioxidant enzyme activity: Within the range of test time and imidacloprid and thiamethoxam concentrations, antioxidant enzyme activity (SOD and CAT) could be induced by imidacloprid and thiamethoxam. With the extension of time, SOD activity exposed to imidacloprid tended to show decrease after the first activation while are suppressed on28th days. CAT activity exposed to imidacloprid performed activation or the same which active change had no obvious relation with time and concentration; With the extension of time, they exposed to thiamethoxam kept no change at the low concentrations (0.3and1.25mg/L) but tended to be inhibited after exposure on14days to28days. While exposed to the high concentration (5mg/L), CAT activity kept activation first and gradually suppressed until return to control as the time changes.(2) ROS:ROS exposed to imidacloprid increased in different concentration groups except keeping no change in3mg/L and the higher the concentration was, the more content ROS had. ROS exposed to thiamethoxam kept the same or increasing.(3) GST enzyme activity:GST activity exposed to imidacloprid was constant first, then activated, finally inhibited as the time changes. GST activity exposed to thiamethoxam only was activated in the high concentration (1.25mg/L,5mg/L) on28days while others were no change.(4) MDA: MDA content exposed to imidacloprid only increased in the high concentration (1.25mg/L,5mg/L) on28days. MDA content exposed to thiamethoxam kept constant first and gradually increasing.(5) In the SCGE test, the results showed that, imidacloprid and thiamethoxam could both cause DNA damage in Danio rerio and DNA damage was enhanced after treatment with different doses of imidacloprid and thiamethoxam on the different times, which showed a good dose-response and time-response relationship.