不同碘营养对大鼠甲状腺Ⅰ型脱碘酶活性及mRNA水平的影响

目的:观察碘缺乏和不同程度碘过量大鼠甲状腺组织Ⅰ型脱碘酶(D1)mRNA的表达及D1活性的变化。方法:断乳1月龄的Wistar大鼠随机分为6组,即低碘(LI)、正常碘(NI)、5倍(5HI)、10倍(10HI)、50倍(50HI)和100倍(100HI)碘组,饲养3、6和12个月后分三批处死动物。采用RT-PCR方法,对甲状腺组织D1mRNA水平进行检测。同时以125I-rT3作为底物,结合离子交换层析技术,测定甲状腺D1活性。结果:与NI组比较,各月龄大鼠LI组D1mRNA表达呈下降趋势,但无统计学差异,各月龄大鼠HI组D1mRNA表达也均呈下降趋势,其中3月龄大鼠5HI、10HI、50HI组、6月龄大鼠100HI组、12月龄大鼠50HI、100HI组D1mRNA表达均显著低于NI组。与NI组比较,各月龄大鼠LI组D1活性均显著升高,各HI组D1活性随碘摄入量的增加而呈逐渐减低趋势,其中6月龄和12月龄50HI及100HI组D1活性则显著降低。结论:碘缺乏情况下,D1活性明显升高,以促进更多的T4转变为T3,但碘缺乏对D1mRNA的表达未见促进作用。碘过量可明显抑制D1活性,且随碘摄入量的增加,D1活性降低更为明显,碘过量对D1mRNA的表达具有一定的抑制作用。

ASSAY OF TYPE I IODOTHYRONINE DEIODINASE ACTIVITY AND mRNA EXPRESSION IN THYROID IN RATS OF DIFFERENT IODINE NUTRITION STATUS

Objective: To further investigate the effects of iodine intake on thyroid function and its possible mechanism. Method: Wistar rats were randomly divided into six groups: LI, NI, 5HI, 10HI, 50HI, 100HI. Different groups of rats were fed with feed and water of different iodine content. 3, 6 and 12 months after administration, they were sacrificed and thyroids were excised. The thyroid D1 mRNA expression level was determined by RT-PCR semi-quantitative method and the thyroid D1 activity was analyzed by using 125I-rT3 as substrate. Results: Compared with NI group, the thyroid D1 mRNA expression was decreased in all HI groups, and D1 activity was significantly higher in LI group and lower in HI groups. There was a tendency of decrease in D1 activity with increased doses of iodine intakes. Conclusion: In the case of iodine deficiency, thyroid D1 activity will increase greatly in order to convert more T4 to T3, but deficient iodine intake doesn’t improve thyroid D1 mRNA expression. Excess iodine can inhibit both thyroid D1 mRNA expression and its activity.