Abstract：
Tail resorption during amphibian metamorphosis is one of the most dramatic processes that is obligatorily dependent on thyroid hormone (TH). Heavy metals could result in thyroid gland damages and disturb TH homeostasis. Lead (Pb) and copper (Cu) often co-exist in natural aquatic ecosystems. However, there is still little information on how tail resorption responds to alone or combined exposure to Pb and Cu. Our study investigated the effects of Pb and Cu alone or combined exposure on the morphological parameters of the tail, histological changes of thyroid gland and tail, and gene expression programs involved in cell death of the tail in Bufo gargarizans tadpoles at the climax of metamorphosis. Results demonstrated that Pb, Cu and Pb-Cu mixture exposure resulted in a significantly longer tail compared with control. Damages to notochord, muscle, skin and spinal cord of the tail were found in Pb and Cu exposure groups. The colloid area, the height of follicular cells and number of phagocytic vesicles of thyroid gland in Pb-Cu mixture exposure groups were significantly reduced. In addition, the expression levels of TH, apoptosis, autophagy, degradation of cellular components and oxidative stress-related genes in the tail were significantly altered following Pb and Cu exposure. The present work revealed the relationship between environmental pollutants and tail resorption, providing scientific basis for amphibian protection.
摘要：
两栖动物变态过程中的尾部吸收是强制性依赖于甲状腺激素（TH）的最戏剧性的过程之一。重金属可导致甲状腺损伤并干扰TH稳态。铅（Pb）和铜（Cu）通常在自然水生生态系统中共存。然而,关于尾巴吸收对单独或联合暴露于Pb和Cu有何反应的信息仍然很少。我们的研究调查了Pb和Cu单独或联合暴露对尾巴形态参数的影响，甲状腺和尾巴的组织学变化，和基因表达程序涉及变态高潮时Bufogargarizanst尾巴的细胞死亡。结果表明,Pb,与对照相比，Cu和Pb-Cu混合物暴露导致明显更长的尾巴。对脊索的损害，肌肉，在铅和铜暴露组中发现了尾巴的皮肤和脊髓。胶体区域，Pb-Cu混合物暴露组甲状腺滤泡细胞高度和吞噬囊泡数量明显减少。此外,TH的表达水平，凋亡，自噬,铅和铜暴露后，尾巴中细胞成分和氧化应激相关基因的降解发生了显着变化。本工作揭示了环境污染物与尾部吸收之间的关系，为两栖动物保护提供科学依据。
