视黄酸对热带爪蟾胚胎致畸效应的表型特征

取典型的胚胎致畸剂——全反式视黄酸对热带爪蟾(Xenopus tropicalis)胚胎进行24，36和48 h暴露.结果表明，2，10和50 μg·L^-1视黄酸暴露对胚胎的存活率没有影响，对胚胎的生长和发育却有明显的抑制作用，并导致所有胚胎出现畸形现象，说明视黄酸对热带爪蟾胚胎具有极强的致畸性，同时显示了热带爪蟾胚胎对视黄酸的敏感性.视黄酸主要引起胚胎脑部缩小、眼睛色素减少、围心腔水肿和尾巴弯曲等多种畸形类型. 24，36和48 h后，暴露组脑部畸形指数和眼睛畸形指数较对照组均有明显增加，并表现出较好的浓度-效应关系，而时间-效应关系不明显，表明视黄酸对脑和眼部的影响主要发生在暴露的前24小时；48 h后尾部的畸形指数相对于24 h有明显的升高.将视黄酸导致的胚胎畸形类型与污染物三丁基锡对比，表明视黄酸致畸特征图谱在三丁基锡致畸机制的研究中有重要的参考价值.由此可见，有可能将FETAX实验发展为一种基于致畸机制的发育毒性检测方法.

Teratogenic phenotypes induced in Xenopus tropicalis embryos by all-trans retinoic acid

In this study, Xenopus tropicalis embryos were exposed to a known teratoen, all-trans retinoic acid (RA), for 24, 36 and 48 h. Exposure to 2, 10 and 50 μg·L^-1 RA showed no effects on the survival rate of embryos, but it significantly inhibited the growth and development of embryos. RA also led to malformations in all embryos, which suggests that RA is a strong teratogen, and 〖WTBX〗X. tropicalis〖WTBZ〗 is very sensitive to RA. The most characteristic malformations were small brains, less pigmentation in eyes, pericardial edema and bent tails. After 24, 36 and 48 h of exposure, the brain teratogenic index and eye teratogenic index were significantly increased in the treatment groups, and these effects showed a good concentration-effect but not time-effect relation. The tail teratogenic index was higher in embryos after 48 h of exposure than that after 24 h of exposure. The comparisons of teratogenic phenotypes induced by RA and tributyltin indicate that RA is a good reference for revealing the mechanisms of tributyltin-mediated teratogenicity. Our results also suggest that FETAX might be modified as an assay to study the mechanisms of contaminants in future.