Teatogenic Effect And Endocrine Disrupting Effects Of Four Triazole Fungicides On Embryos And Tadpole Of Xenopus Tropicalis

Triazole fungicide is the largest class of fungicides used in China, with its broad-spectrum and other advantages of widely used in rice, fruits and vegetables and other crops. In this paper, four triazole fungicides Tebuconazole, Triadimefon, Tricyclazole and Hexaconazole were used in this study. The growth effects of Xenopus tropicalis exposed to four fungicides were observed including acute toxicity,embryo teratogenic effects, abnormal development, thyroid endocrine disruption effect The results of the study is the following three aspects:First of all, It was determined that Tebuconazole was more sensitive to Xenopus tropicalis at ambient concentrations than the other three pesticides through acute toxicity test and frog embryo teratogenesis assay-Xenopus (FETAX). Under the envirmental concentration of 0.02 mg/L, the mortality rate of Tebuconazole treated group was I5% and the malformation rate was 7.5%, which was significantly higher than that of Triadimefon and Hexaconazole. Theedema of the abdomens, notochord bending, tail bending and tail short and other deformities was found when tropical Xenopus embryos was exposed to Tebuconazole. It was showed that the mortality and teratogenicity of tropical Xenopus embryos exposed to Tebuconazole was increasing at the same concentration in the four triazole fungicides.Secondly, the results showed that the length of hindlimb of Xenopus tropicalis tadpoles exposed to Tebuconazole for 7 d was significantly shorter than that control group of 7d, but there was no significant difference in the weight and SVL; after exposure to 21 d in the 2 mg/L group, the weight, SVL and hindlimb length were significantly lower than the control group. The growth and development of tropical Xenopus tropicalis could be inhibited under the low concentration of Tebuconazole.Finally, the HPT axis-related genes(nis, tra, tr?, ttr, tshr, dio2, dio3) expression were detected by real-time fluorescence quantitative detection and the levels of thyroid hormones were detected by ELISA kit after the 7 days and 21 days of the tadpoles Xenopus tropicalis exposed to Tebuconazole. The results showed that the T3 and T4 hormone levels of tadpoles Xenopus tropicalis exposure to Tebuconazole 2 mg/L for 21 d increased. The expression levels of nis, ttr, tshr and dio2 increased significantly at 2mg/L after 7d exposure, while tr a and tr ? had no significant difference compared with the control group. the expression levels of the other 6 genes except dio3, increased significantly after 21 days of thehigh concentration exposure. The difference of thyroid hormone level and transcriptional level of HPT axis-related gene indicated that Tebuconazole had obvious thyroid endocrine disruption to tropical Xenopus tropicalis.