Carlsson Gunnar, Norrgren Leif
Swedish University of Agricultural Sciences, Faculty of Veterinary Medicine and Animal Science, Department of Biomedicine and Veterinary Public Health, Division of Pathology, Pharmacology and Toxicology, Uppsala, Sweden.
Aquat Toxicol. 2007 Apr 20;82(1):55-62. doi: 10.1016/j.aquatox.2007.01.005. Epub 2007 Jan 30.
This study investigated the suitability of using tadpoles of the West-African clawed frog (Xenopus tropicalis) for studying adverse effects on the thyroid hormone system after chemical exposure. Tadpoles were exposed to the thyroxine synthesis inhibitor 6-propylthiouracil (PTU) at concentrations between 2-75mg/L during 14 days. After 5 and 14 days of exposure the developmental stage, hind limb length, body length and weight were measured. Moreover, histological measurements of the thyroid glands were performed after 14 days of exposure. These measurements included maximum thyroid cross-section area, follicular area and epithelial cell height. Tadpoles in the 75mg/L treatment were less developed and had shorter hind limb length than the control group after 14 days of exposure. No effects were recorded on these parameters at lower PTU concentrations. The histological measurements revealed clear dose-response relationships in both follicular cross-section area and epithelial cell height, with lowest observed effect concentrations (LOECs) recorded at 2 and 5mg/L, respectively. This study shows that X. tropicalis is a suitable species for detection of thyroid disrupting chemicals. Further, histopathological measurements of thyroid glands are more sensitive parameters compared with apical endpoints when studying adverse effects on thyroid hormone system caused by PTU exposure in X. tropicalis.
本研究调查了使用西非爪蟾（热带爪蟾）蝌蚪来研究化学物质暴露后对甲状腺激素系统的不良影响的适用性。将蝌蚪在14天内暴露于浓度为2-75mg/L的甲状腺素合成抑制剂6-丙基硫氧嘧啶（PTU）中。在暴露5天和14天后，测量发育阶段、后肢长度、体长和体重。此外，在暴露14天后对甲状腺进行组织学测量。这些测量包括甲状腺最大横截面积、滤泡面积和上皮细胞高度。暴露14天后，75mg/L处理组的蝌蚪发育程度低于对照组，后肢长度也较短。在较低的PTU浓度下，这些参数未记录到影响。组织学测量显示，滤泡横截面积和上皮细胞高度均呈现明显的剂量-反应关系，最低观察到效应浓度（LOECs）分别记录为2mg/L和5mg/L。本研究表明，热带爪蟾是检测甲状腺干扰化学物质的合适物种。此外，在研究PTU暴露对热带爪蟾甲状腺激素系统造成的不良影响时，与顶端终点相比，甲状腺的组织病理学测量是更敏感的参数。
