Department of Disease Model, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan.
Tissue and Histopathology Section, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan.
Endocr J. 2020 Feb 28;67(2):231-240. doi: 10.1507/endocrj.EJ19-0245. Epub 2019 Nov 19.
Exposure to ionized radiation in childhood has been recognized as a risk factor for the development of thyroid cancer and possibly for other thyroid disorders. However, the effects of neonatal radiation exposure on thyroid morphology and functions have never been explored despite its potential importance. One-week-old male Wistar rats were subjected to cervical X-irradiation at 6 and 12 Gy. Animals were examined at the ages of 2, 8 and 18 weeks old. For comparison, 8-week-old rats were cervically X-irradiated at the same doses. Thyroid histology was examined by computer-assisted microscopy to measure areas of colloid and epithelium of thyroid follicles as well as epithelial heights. In rats that received cervical X-irradiation at 1 week old, the colloid size of thyroid follicles decreased at the age of 8 weeks old in a radiation-dose dependent manner. This morphological change was persistently found at 18 weeks old. There were no significant differences in serum total T3 or T4 levels among the groups. Serum TSH levels increased significantly in 8-week-old rats neonatally X-irradiated. Thyroglobulin (Tg) mRNA and protein expressions were significantly decreased in the neonatally-irradiated group while thyroid peroxidase mRNA express increased at 18 weeks old. None of these changes were observed in the rats X-irradiated at 8 weeks old. In conclusion, our results clearly demonstrated that neonatal rat thyroid was sensitive to ionized radiation, developing specific morphological changes characterized by smaller thyroid follicles along with changes in serum TSH levels and Tg expressions in the thyroid tissue.
儿童时期接触电离辐射已被认为是甲状腺癌发展的一个风险因素，也可能是其他甲状腺疾病的一个风险因素。然而，尽管新生儿辐射暴露具有潜在的重要性，但尚未探索其对甲状腺形态和功能的影响。1 周龄雄性 Wistar 大鼠在 6 和 12 Gy 时接受颈部 X 射线照射。动物在 2、8 和 18 周龄时进行检查。为了进行比较，8 周龄大鼠在相同剂量下接受颈部 X 射线照射。通过计算机辅助显微镜检查甲状腺组织学，以测量甲状腺滤泡的胶体和上皮面积以及上皮高度。在 1 周龄接受颈部 X 射线照射的大鼠中，甲状腺滤泡的胶体大小在 8 周龄时以剂量依赖性方式减小。这种形态变化在 18 周龄时仍然存在。各组血清总 T3 或 T4 水平无显著差异。在 8 周龄时接受新生儿 X 射线照射的大鼠中，血清 TSH 水平显著升高。甲状腺球蛋白（Tg）mRNA 和蛋白表达在新生照射组中显著降低，而甲状腺过氧化物酶 mRNA 表达在 18 周龄时增加。在 8 周龄时接受 X 射线照射的大鼠中未观察到这些变化。总之，我们的结果清楚地表明，新生大鼠甲状腺对电离辐射敏感，表现为甲状腺滤泡变小，同时伴有血清 TSH 水平和甲状腺组织中 Tg 表达的变化。
