Re-evaluation of thyroid hormone signalling antagonism of tetrabromobisphenol A for validating the T3-induced Xenopus metamorphosis assay
The authors developed the T3-induced Xenopus metamorphosis assay, which is supposed to be able to sensitively detect thyroid hormone (TH) signalling disruption of chemicals. The present study aimed to validate the T3-induced Xenopus metamorphosis assay by re-evaluating the TH signalling antagonism of tetrabromobisphenol A (TBBPA), a known TH signalling disruptor. According to the assay, Xenopus tadpoles at stage 52 were exposed to 10-500nmol/L TBBPA in the presence of 1nmol/L T3. After 96hr of exposure, TBBPA in the range of 10-500nmol/L was found to significantly inhibit T3-induced morphological changes of Xenopus tadpoles in a concentration-dependent manner in term of body weight and four morphological endpoints including head area (HA), mouth width (MW), unilateral brain width/brain length (ULBW/BL), and hind-limb length/snout-vent length (HLL/SVL). The results show that these endpoints developed are sensitive for characterising the antagonistic effects of TBBPA on T3-induced metamorphosis. Following a 24-hr exposure, we found that TBBPA antagonised expression of T3-induced TH-response genes in the tail, which is consistent with previous findings in the intestine. The authors propose that the tail can be used as an alternative tissue to the intestine for examining molecular endpoints for evaluating TH signalling disruption. In conclusion, these results demonstrate that the T3-induced Xenopus metamorphosis assay we developed is an ideal in vivo assay for detecting TH signalling disruption.
Authors: Wang Y, Li Y, Qin Z, Wei W. ;Full Source: Journal of Environmental Science (China). 2017 Feb; 52:325-332. doi: 10.1016/j.jes.2016.09.021. Epub 2016 Nov 24. ;