College of Life Sciences, Shaanxi Normal University, Shaanxi, China.
Environ Toxicol Chem. 2018 Jan;37(1):213-223. doi: 10.1002/etc.3947.
The present study examined the effects of chronic cadmium (Cd) exposure on metamorphosis, body size, thyroid gland, and skeletal development of Chinese toad (Bufo gargarizans) tadpoles. Tadpoles were exposed to Cd concentrations at 0, 5, 10, 50, 100, and 500 μg/L from Gosner stages 26 to 46 of completion of metamorphosis. Our results showed that 100 and 500 μg/L of Cd concentrations increased mortality and decelerated metamorphosis rate. In addition, significant body size reduction at Gosner stage 42 was observed at 100 and 500 μg/L of Cd treatments (p < 0.01). Average body length and hind-limb length were significantly decreased in the 500 μg/L of Cd group (p < 0.05) but body mass was not significantly different at Gosner stage 46. Moreover, bone formation was delayed in high Cd concentration treatments (50, 100, and 500 μg/L) at both Gosner stage 42 and 46. Histopathological changes of the thyroid gland showed that follicular cell hyperplasia and malformation were induced by high Cd concentrations (50, 100, and 500 μg/L). Furthermore, real-time polymerase chain reaction analysis suggested that the larvae exposed to high-dose Cd exhibited a significant decrease in deiodinase (Dio2) and thyroid hormone receptor (TRβ) mRNA levels at Gosner stage 42 and 46. Our investigation indicated that high-dose Cd caused metamorphic deceleration, body size reduction, and delayed skeletal development through disrupting the thyroid system in B. gargarizans larvae. Environ Toxicol Chem 2018;37:213-223. © 2017 SETAC.
本研究考察了慢性镉（Cd）暴露对中华蟾蜍（Bufo gargarizans）蝌蚪变态、体型大小、甲状腺和骨骼发育的影响。从变态完成的 Gosner 阶段 26 到 46 期，蝌蚪暴露于 0、5、10、50、100 和 500μg/L 的 Cd 浓度中。结果表明，100 和 500μg/L 的 Cd 浓度增加了死亡率并减缓了变态率。此外，在 100 和 500μg/L 的 Cd 处理下，Gosner 阶段 42 时观察到显著的体型减小（p<0.01）。在 500μg/L 的 Cd 组中，平均体长和后肢长度显著减小（p<0.05），但在 Gosner 阶段 46 时体重无显著差异。此外，在高 Cd 浓度处理（50、100 和 500μg/L）下，骨形成在 Gosner 阶段 42 和 46 均延迟。甲状腺的组织病理学变化表明，高浓度 Cd 诱导滤泡细胞增生和畸形（50、100 和 500μg/L）。此外，实时聚合酶链反应分析表明，暴露于高剂量 Cd 的幼虫在 Gosner 阶段 42 和 46 时，脱碘酶（Dio2）和甲状腺激素受体（TRβ）mRNA 水平显著下降。我们的研究表明，高剂量 Cd 通过破坏 B. gargarizans 幼虫的甲状腺系统，导致变态迟缓、体型减小和骨骼发育延迟。环境毒理化学 2018；37:213-223。©2017 SETAC。
