高碘对大鼠甲状腺形态、血清甲状腺激素及TPO mRNA表达的影响

The Effects of Iodine Excess on the Thyroid Morphology and Serum Thyroid Hormones and Expression of TPO mRNA in Rats

目的观察长期碘过量对大鼠甲状腺形态、血清甲状腺激素及TPO mRNA表达的影响,并探讨其作用机制。方法断乳1月龄的SD大鼠随机分为对照组(Control)、高碘Ⅰ组(H IⅠ)、高碘Ⅱ组(H IⅡ),分别饮用碘浓度不同的水,饲养6个月后处死,摘取甲状腺,在光镜和电镜下观察甲状腺形态结构的变化;采用放射免疫方法测定血清甲状腺激素水平;RT-PCR检测甲状腺过氧化物酶(Thyriod peroxidase,TPO)mRNA的表达。结果高碘组有部分滤泡明显增大,滤泡腔内充满浓染胶质。对照组、H IⅠ、H IⅡ的血清TT3、TT4呈逐渐下降趋势,但各组间差异无统计学意义(P>0.05);H IⅠ、H IⅡ组甲状腺TPOmRNA表达水平比对照组显著降低(P<0.05)。结论长期摄入过量碘可造成甲状腺组织学改变,并且抑制甲状腺TPO 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。

Objective To observe the effects of iodine excess on thyroid morphology and serum thyroid hormones, the expression of thyroid peroxidase mRNA, and to explore its mechanism. Methods One - month SD rats were divided into three groups ： control, high iodine Ⅰ （ HI Ⅰ ）, high iodine Ⅱ （ HI Ⅱ ）, fed with water containing different iodine concentration by adding KIO3 respectively. Rats were sacrificed after being fed for six months. The morphology of thyroid was investigated under light microscope and electron microscope, using radio - immunoassay and RT -PCR method, the serum thyroid hormones and ratio of TPO/13 - actin were measured. Results The major changes included increased follicles with colloid accumulation in HI groups. The levels of serum thyroid hormones was decreased gradually from control to HI group, but there were no remarkable differences among three groups （ P 〉 0. 05 ）. The TPO mRNA expression decreased gradually from control to HI groups . Conclusions Chronic iodine excess leads to definite histological changes in rat thyroid, and inhibits the expressions of TPO mRNA as well as thyroid hormone synthesis, which in turn acts as a protective mechanism against iodine excess.