Teratogenic effects of tetrabromobisphenol A on Xenopus tropicalis embryos

Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant and a known thyroid disruptor. We reported exposing Xenopus tropicalis embryos (NF10) to 0.01, 0.1 or 1 mg/L of TBBPA with or without 70 µg/L triiodothyronine (T3). Compared with the controls, 1 mg/L of TBBPA significantly reduced the body length of embryos after 24, 36 and 48 h of exposure. Embryos treated with TBBPA showed multiple malformations, including: abnormal eyes, skin hypopigmentation, enlarged proctodaeum, narrow fins and pericardial edemas. The effect of abnormal eyes manifested itself in the loss of pigmentation, reduction in size, or absence of external eyes. The degree of eye malformations was quantified with the index of eye malformations (IEM) with 0 being normal and 3 being severe. In the 1 mg/L TBBPA treatment groups, the incidence of total malformations (ITM) was 68–93%, and IEM was 0.8–0.9. T3 showed no teratogenic effects on embryos, but it significantly enhanced TBBPA-induced teratogenic effects. In the T3 + 1 mg/L TBBPA treatment groups, ITM was 91–99%, and IEM was 1.8–1.9. Histological observations showed that the retinas were generally smaller, and the lenses were underdeveloped or even absent. These results indicate that TBBPA at relatively high concentration has teratogenic effects on X. tropicalis embryos. The results also suggest that thyroid hormone signaling might be involved in TBBPA induced-teratogenicity.