The Effect Of Organotin Compounds On Genes MRNA Expression Of Xenopus Tropicalis

In recent years, amphibian populations have declined dramatically. The causes of such declines may be related to environmental pollutants. The organotin compounds are known as endocrine disrupting chemical (EDCs). TBT is considered to be the most toxic substance ever introduced into the marine environment. The Amphibian Metamorphosis Assay (AMA) was conducted to determine the potential thyroid hormone disrupting effect. Morphological and histological endpoints are often used in AMA. In this paper, we used molecular markers to determine the thyroid hormone disrupting effect of two organotin compounds. We studied the effects of organotin compounds on changes of mRNA expressions in development of Xenopus tropicalis tadpoles and embryos, and discussed their endocrine disrupting effects and possible mechanisms.First of all, X. tropicalis tadpoles (NF51) were exposed to TBT for 48 and 96 h. Exposure to 50 and 200 ng-L-1 TBTC1 showed no effects on the survival rate of tadpoles, and suggest that TBT can result in the changes of multiple genes expressions and show high tissue-specific differences. These genes are involved in the synthesis, transportations, transformations and actions, which indicate that TBT shows thyroid hormone disrupting effects. The changes of related genes indicate that TBT might disrupt the thyroid hormone system of tadpoles by binding with retinoid X receptor.Secondly, X. tropicalis embryos were exposed to TBT for 24,48 and 72 h. The results show that TBT can result in the changes of several genes expression. These genes involved in thyroid hormone signal regulating way, head development and migration way of neural crest cell for multiple processes, and show that TBT affect the development process of X. tropicalis embryos. Meanwhile, through detect thyroid hormone receptor genes and their related gene show that TBT also have thyroid hormone disturbance effect in X. tropicalis embryos. Some mRNA expressions abnormalities affected the process of embryonic development, leading to teratogenic effect.Finally, X. tropicalis embryos were exposed to 0.2,1 and 5μg-L-1TPT for 72 h. TPT can induce the changes of many genes expressions in embryonic tail, and primary study its molecular mechanism of malformation. Foxd 3 abnormal expression induces the body axis abnormalities, maybe related to the bending of embryonic tail. But not do so many genes, we still need further experiment to study its teratogenic. mechanism, revealing some abnormal phenomenon such as narrow fm.The changes of related genes indicate that organotin compounds disrupt the thyroid hormone system of tadpoles and embryos and affect the process of development of Xenopus. Organotin compounds might be one of the reasons leading to the decline of amphibian embryos. At the same time, we also studied the molecular mechanism of abnormal eye and bend tail introduced by organictin compounds. Therefore, if we add critical genes'expressions as the markers of AMA, it would not only increase the power to screen the thyroid disrupting chemicals but also provide clues for revealing the mechanisms of contaminants.