不同碘摄入水平对小鼠子二代鼠甲状腺功能和形态学的影响

目的研究不同碘摄入水平对小鼠子二代鼠甲状腺功能和形态学的影响。方法将断乳1个月Balb/c小鼠随机分为5组：低碘组LI、适碘组NI、5倍高碘组5HI、10倍高碘组10HI、50倍高碘组50HI。给以不同浓度碘水〈0.25μg（LI）、1.5μg（NI）、7.5μg（5HI）、15μg（10HI）、75μg（50HI）]喂养3个月后,连续传2代。各组子二代鼠20,40日龄时处死,采用放射免疫法测定血清甲状腺激素水平,并作甲状腺形态学观察,用图文分析系统测定甲状腺滤泡的体视学参数：滤泡平均面积（SA）、滤泡腔平均面积（SB）、上皮细胞层厚度（L）和滤泡腔体积与滤泡体积之比（VA）,以期为甲状腺结构改变提供定量依据。结果 20日龄时,与NI组相比,LI组与50HI组T4明显降低;40日龄时,与NI组相比,LI组T4明显降低。形态学观察,NI组甲状腺多为中等大小滤泡,上皮细胞多为单层立方状;LI组甲状腺呈明显的滤泡增生,上皮呈柱状多为复层;50HI组甲状腺与适碘组比较,上皮细胞变扁平,腔内蓄积大量胶质。体视学参数测定：LI：L,SA均明显增大,VA明显减低;5HI组和10HI组与NI组比较各项指标之间均无统计学差异。50HI组,L明显减低,SA,SB,VA均明显增大。结论碘缺乏及高剂量碘过量均可引起子二代鼠的甲状腺功能低下。碘缺乏时子二代小鼠发生了明显的滤泡增生性甲状腺肿;高碘摄入时子二代小鼠发生了胶质蓄积性甲状腺肿,但肿大程度远不及缺碘所致的肿大。子二代小鼠对碘过量有较强耐受性,当碘摄入量为正常50倍时,才会明显影响到甲状腺的形态。

Effect of Different Levels of Iodine Intake on Thyroid Function and Morphology in Second Generation（F2） Balb/c Mice

Objective To study the morphological and functional alterations of the thyroid gland in the second filial generation（F2） of Balb/c mice subjected to different levels of iodine intake.Methods The mice were randomly divided into five groupsless iodine group（LI）,normal iodine group（NI）,5-fold excessive iodine group（5HI）,10-fold excessive iodine group（10HI）,and 50-fold excessive iodine group（50HI）] and given drinking water containing iodine in different concentrations daily intake0.25 μg（LI）,1.5 μg（NI）,7.5 μg（5HI）,15 μg（10HI）,75 μg（50HI）].After three months,the mice were mated and their 20-day and 40-day old second filial generations were observed.Stereological parameters including the thickness of the epithelial layer（L）,the area of the follicle（SA）,the area of follicular lumen（SB）,and the ratio of follicular lumen and follicle volume VA） were measured using a photo analytic system to provide a basis for the quantitative evaluation of thyroid gland changes.Results The serum thyroxin T4 level in the 20-day old and 40-day old F2 mice of the LI and 50 HI groups were significantly lower than the normal control group.Histopathological examination revealed that in the NI group,the thyroid gland follicles were of median size,and the most follicular epithelium consisted of a single-layer of cuboidal epithelial cells.In the LI group,there was apparent follicular hyperplasia,and the epithelium was columnar and stratified.In the 50HI group,the epithelium was more flat than that in the NI group,and plenty of colloid was accumulated in the follicular lumen.Assessment of the stereological parameter showed that in the LI group,L and SA were increased,VA was decreased.The data of the 5HI and 10HI groups were similar to those of the NI group.In the 50HI group,L was significantly decreased,and SA,SB and VA were significantly increased.Conclusions Both iodine deficiency and excess may cause hypothyroidism in the second filial generation mice.Iodine deficiency produces apparent follicular hyperplasia goiter,and long-term excessive iodine intake may result in colloid cumulative goiter,but the enlargement of thyroid by iodine excess is much less than that by iodine deficiency.The second filial generation mice have a high tolerance of excessive iodine.Obvious morphological changes often occur when the iodine intake excess reaches 50-fold higher than that in normal mice.