Project for development of in vivo rat model internal 131-iodine exposure in thyroid grand

1986年切尔诺贝利灾难后，那里的儿童甲状腺癌人数增加了。1991年至1996年，我们加入了切尔诺贝利笹川卫生和医疗合作项目。我们在5年中对13000多名儿童进行了筛查。儿童甲状腺癌的发病率是日本的100倍。不幸的是，在事故发生时，我们没有关于这些患者直接甲状腺剂量的数据。辐射与甲状腺癌之间的直接关系尚不清楚。另一方面，以前的报告显示，在使用碘-131诊断或治疗的患者中，甲状腺癌的发病率没有增加。为了阐明放射性碘摄入是否会导致甲状腺癌，我们尝试建立了碘-131内暴露的动物模型。将碘-131（0、0.2、0.6、1Mbq）腹腔注射给先前低碘饮食的大鼠（每组10只）。照射后1、2、6、12个月，处死大鼠进行病理分析。我们观察到暴露的大鼠甲状腺肿瘤没有增加。由于被检查的老鼠数量不足以进行统计分析，因此该结果无法得出任何具体结论。此外，我们推测大鼠的种类和年龄与辐射暴露后引起甲状腺肿瘤的敏感性有关。未来，我们将进一步研究甲状腺癌与碘-131暴露之间的关系。

After Chernobyl disaster at 1986, the number of childhood thyroid cancer increased there. We were joining the Chernobyl Sasakawa Health and Medical Cooperation Project form 1991 to 1996. We screened more than 13000 children during 5 years. The incidence of childhood thyroid cancer is 100 times higher than Japan. Unfortunately, we did not have the data about the direct thyroid dosimetory of these patients at the time of the accident. The direct relationship between radiation and thyroid cancer is still uncertain. On the other hand, previous reports showed no increase of thyroid cancer among patients who were diagnosed or treated using Iodine-131. To elucidate whether radio-iodine intake cause thyroid cancer, we have tried to make animal model that is internally exposed by Iodine-131. Iodine-131(0, 0.2, 0.6, 1Mbq) was peritoneally injected to rats that previously took low iodine diets (n=10/each group). One, two, six or twelve months after radiation exposure, rats were sacrificed and analyzed pathophigiologically. We observed no increase of thyroid tumor among exposed rats. The result does not lead to any concrete conclusions because the number of examined rats is not good enough to statistically analyze. Furthermore, we speculate that rat spicies and their ages relate to sensitivity to cause thyroid tumors following radiation exposure. In future, we win further examine to answer the relationship between thyroid cancer and Iodine-131 exposure.