不同碘摄入量大鼠甲状腺功能及其TG、TPO mRNA的表达

目的：从基因表达水平研究不同碘摄入量对大鼠甲状腺功能的影响，方法：Wistar大鼠分为低碘，适碘，高碘三组，观察尿碘含量，血清及甲状腺组织激素水平，甲状腺组织甲状腺球蛋白（TG），甲状腺过氧化物酶（TPO）mRNA 的表达，结果：低碘组血清及组织T4，T3明显降低，尿碘含量显著减少，甲状腺TPO mRNA表达显著升高，而TG mRNA表达明显降低，高碘组血清T4呈下降趋势，甲状腺组织T4下降明显，尿碘显著增高，甲状腺TPOmRAN表达明显降低，高碘组血清T4呈下降趋势，甲状腺组织T4下降明显，尿碘显著增高，甲状腺TG，TPO mRNA表达均显著降低。结论：长期低碘造成大鼠甲状腺功能严重低下，甲状腺TPO mRNA表达呈代偿性增强，而TG mRNA有达显著降低，碘摄入过多抑制甲状腺TPO mRNA,TG mRNA的表达，从而造成甲状腺激素合成降低。这是甲状腺的一种自身保护机制，也是对长期高碘的一种适应.

Thyroid function and expressions of thyroglobulin and thyroid peroxidase mRNA in rats at different iodine intake levels

Objective　To study the effects of different iodine intake levels on thyroid function at gene expression level in rats. Methods　Wistar rats were divided into normal iodine (NI), lower iodine (LI) and higher iodine groups (HI). The urinary iodine excretion, T4 and T3 of serum and thyroid tissue were measured, the expressions of thyroglobulin (TG) and thyroid peroxidase (TPO) mRNA in thyroid were determined by RT-PCR. Results　In LI group, the urinary iodine excretion, T4, T3 of serum and thyroid tissue were lower, the expression of TPO mRNA increased markedly, while TG mRNA decreased significantly. In HI group, T4 showed a decreasing tendency in serum and was markedly reduced in thyroid tissue, along with significantly higher urinary iodine excretion and decreased expressions of TPO mRNA and TG mRNA. Conclusion　Lower iodine intake for long term results in severe hypothyroidism, and compensatory increase of TPO mRNA expression but decrease of TG mRNA expression; higher iodine intake inhibits the expressions of both TPO、 TG mRNA as well as thyroid hormone synthesis, which in turn acts as a protective mechanism against iodine excess.