Effects And Mechanism Of Herbicide Acetochlor On Tadpole Liver Of Bufo Raddei

With the fast development of industry and agriculture, and the rapid increase of the population, environment pollution has been more and more serious, and pesticide pollution has been giving global concern. As the transition from the aquatic to the terraneous, amphibians play a key role in protecting the system of the agriculture and stockbreeding or keeping the nature ecosystem balance. But also amphibians have the sensitivity to changes of their habitat and their larvae must live in the aquatic environment, hence the pollution has been an important cause of amphibian population declines. Various studies have proved that amphibians are regarded as bio-indicators of environmental inspecting.In the paper, through the subacute toxicity test, using Bufo raddei as experimental material, the aim of experiment is to evaluate the toxicity and toxic mechanism of herbicide acetochlor in the liver of B. raddei. Chosen experimental index that include the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and the content of MDA, DNA-single strand break, changes on tissue, reflect toxic effects from two aspects on the levels of molecule and tissue. The results showed as follows:By detecting the activities of three antioxidant enzymes in tadpole liver, the results showed that acetochlor significantly reduced the activities of antioxidant enzymes, suggesting that acetochlor induced oxidative stress in B. raddei. Moreover with the increase of acetochlor concentrations, the activities of SOD or GSH-Px occurred sharply changes which reflected a higher sensitivity to pollution environment, hence SOD, or GSH-Px is the best biomarker in biological monitoringThe MDA levels of tadpole liver were of linear enhancement with increasing concentrations of ACETO, and 1.17-fold at 0.017mg/l, 1.71-fold atmg/l and 1.96-fold at 0.068 mg/l were higher than that of control respectively, suggesting that acetochlor cause lipid peroxidation and accumulate excessive reactive oxygen species (ROS) in tadpole liver.By the alkaline single cell gel electrophoresis assay (SCGE) to analysis DNA damage, the significant increase in the level of DNA-SSB indicates that ACETO induces a dose-dependent manner in DNA damage as well, and 5.12-fold,5.58-fold,7.39-fold at 0.017,0.034,0.068 mg/l were higher than that of ACETO exposure alone(0.068 mg/l) in tail moment.Basing on those obtained results, we speculate that ACETO-induced DNA damage should be a consequence of the generation of ROS.A/-acetyl-l-cysteine (NAC) or melatonin (MEL) is adminstrated, prior to ACETO exposure. The decrease of DNA-SSB level and the increase of total antioxidant capability (TAC) show that ACETO-caused DNA damage can be attenuated by NAC and MEL. In addition, a negative correlation was observed between the extent of DNA damage and the level of TAC in tadpole liver. In conclusion, the results suggest that ACETO-induced DNA damage is mediated by ROS.The liver pathology showed that small holes and cell number increased, and cell appeared chips, even cell necrosis.From this study, ACETO do harms to B. raddei tadpoles by affecting antioxidant enzymes activities, causing lipid peroxidation of tadpole liver, inducing DNA-single strand break and destroying issues of tadpole liver. All of damage mechanisms are possibly relative to enhanced accumulation of ROS in tadpole liver.