黑斑蛙变态过程中甲状腺发育及甲状腺激素分泌

系统研究了我国本土两栖动物种黑斑蛙（Rana nigromaculata）变态发育过程中甲状腺组织学和甲状腺激素水平的变化，为甲状腺生物学和甲状腺干扰研究提供基础数据。黑斑蛙蝌蚪发育的形态变化: 第26-40阶段，后腿芽生长并逐渐分化出五趾结构；42阶段，开始进入变态高峰期，前肢展开，尾吸收，蝌蚪身体发生巨大形变；46阶段，蝌蚪完全变态成小蛙。随着形态学的变化，甲状腺的组织结构也发生明显的变化: 26-37阶段，甲状腺体积较小，增长缓慢；38阶段甲状腺体积迅速膨大，进入高峰期，甲状腺的发育达到顶峰；随着变态完成，甲状腺又逐渐缩小。甲状腺组织学变化的同时，甲状腺激素水平也相应发生变化: 在变态前期，下颌中3，3'，5-三碘代-L-甲腺原氨酸（T3）水平增长缓慢，进入变态期后，T3含量迅速升高，在变态高峰期达到峰值，随后下降。以上结果表明，黑斑蛙发育过程中甲状腺组织学的变化与甲状腺激素水平的波动相吻合。对黑斑蛙甲状腺系统的研究，可为日后使用黑斑蛙开展甲状腺干扰作用的研究提供基础。  

THE DEVELOPMENT AND HORMONE LEVELS OF THYROID GLAND DURING RANA NIGROMACULATA METAMORPHOSIS

The metamorphosis of amphibians is considered as a good model to study thyroid hormone (TH) disruption. In the present study, we used Rana nigromaculata, a domestic species, to investigate thyroid development and the changes in TH levels during metamorphosis.We first described the morphological change during the tadpole development (stage 26-46) that the hind limbs appeared and finally formed five toes from stage 26 to 40. At the climax of metamorphosis, the dramatic changes include the protruded forelimbs and start-to-resorb tail. Tail resorption completed at stage 46, indicating the completion of metamorphosis. Corresponding to the morphological changes, histological features of thyroid gland changed significantly. From stage 26 to 37, the thyroid gland was small and developed slowly. At stage 38, the thyroid gland enlarged dramatically. The climax of thyroid gland development happened at the climax of metamorphosis. The thyroid gland began to shrink at the completion of metamorphosis. The thyroid hormone (T3) levels were associated with thyroid gland development. T3 content in per lower jaw was very low before metamorphosis, while increased dramatically during metamorphosis; it reached the peak level at the climax of metamorphosis and then decreased. During Rana nigromaculata metamorphosis, thyroid hormone levels were correlated with thyroid gland histological features. The current study creates the foundation for the research of thyroid hormone disruption.