Screening thyroid hormone disrupting effects of cadmium using Xenopus metamorphosis assay
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摘要: 将NF51阶段非洲爪蟾(Xenopus laevis)蝌蚪暴露于Cd2+浓度为0.01,0.1和1 mg·L-1的溶液中21 d,观测Cd2+对爪蟾的生长、变态和甲状腺组织结构的影响.1 mg·L-1Cd2+暴露组爪蟾蝌蚪与对照组相比,7 d后,平均体重减少了0.39倍,体长和后肢长分别减少了0.17倍和0.27倍,发育阶段稍有延缓;21 d后,1 mg·L-1Cd2+暴露组爪蟾蝌蚪后肢长减小了0.11倍,延缓了1个发育阶段.其余各浓度组在7 d和21 d暴露后,体重、体长、后肢长和发育阶段与对照组无显著差异.21 d后,Cd2+各浓度组甲状腺组织结构出现滤泡数目减少、胶质减少甚至空泡化等现象,1 mg·L-1Cd2+暴露组甲状腺滤泡之间还出现溶通现象.结果表明CdCl2具有甲状腺激素干扰效应,并可能是由于该化合物直接作用于甲状腺组织引起.由此可见,爪蟾变态实验可以有效检测重金属盐的甲状腺激素干扰效应.Abstract: Xenopus laevis tadpoles (NF51) were exposed to cadmium chloride at the concentrations of 0.01, 0.1and 1 mg·L-1Cd2+ for 21 days. The changes of growth, metamorphosis and thyroid gland of X. laevis were observed. Compared with the control, the body weight (BW), snout to vent length (SVL) and hind limb length (HLL) were decreased by 0.39, 0.17 and 0.27 fold in 1 mg·L-1Cd2+treatment group after exposure for 7 days, respectively. The hind limb length (HLL) was decreased by 0.11 fold and the development showed one stage slower in 1 mg·L-1 treatment group after exposure for 21 days. And the other treatment groups did not show significant changes in BW, SVL, HLL or development stages after exposure for 7 and 21 days. Cadmium chloride treatment decreased the number of follicle, and induced the depletion of colloid and even vacuolation after exposure for 21 days. In addition, amalgamation of two or more follicles occurred in 1 mg·L-1 treatment group. Our results suggested that cadmium chloride had thyroid hormone disrupting effects and might disturb thyroid gland tissue directly. Therefore, AMA was further proved to be a valid tool to screen the thyroid hormone disrupting effect of heavy metal salt.
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