不同碘摄入水平对大鼠甲状腺功能影响的实验研究

目的研究不同碘摄入水平对大鼠甲状腺功能的影响。方法将Wistar大鼠分为低碘(LI)组、正常碘(NI)组、5倍、10倍、50倍、100倍高碘(5HI、10HI、50HI、100HI)组,在喂养3、6、12个月后处死,分别检测血清总T4(TT4)、总T3(TT3)、游离T3(FT3)、游离T4(FT4)、反T3(rT3)水平,以及甲状腺组织中T4、T3、rT3水平。结果3个月时血清TT4、FT4、TT3、FT3、rT3以及甲状腺组织中T4、T3、rT3水平,组间比较差异均有统计学意义(F值分别为54．07、67．80、15．51、27．71、19．73、61．51、40．67、53．86,P<0．01);6个月时上述指标组间比较差异均有统计学意义(F值分别为58．80、58．75、19．64、17．22、47．21、46．01、47．22、126．87,P<0．01);12个月时甲状腺组织中T4、T3、rT3水平组间比较差异均有统计学意义(F值分别为20．44、17．69、29．23,P<0．01)。与NI组相比较,LI组血清和甲状腺组织内各激素水平明显降低,而高碘组随着时间的延长和摄入碘量的增加,血清各激素和甲状腺组织内T3水平出现逐渐降低趋势。结论碘缺乏和碘过量均可导致大鼠甲状腺功能低下,而碘缺乏的作用更明显;大鼠对长期高碘摄入比碘缺乏具有更强的耐受性,只有在长期补充过量碘(>50倍正常需要量)才发生甲状腺功能低下。

Experimental study on the relationship between different iodine intakes and their thyroid function in rats

Objective To study the effect of different iodine intake (KI) on the thyroid function in Wistar rats. Methods Wistar rats were divided into iodine deficiency (LI), control (NI), and iodine excess groups of 4 levels [5-folds (5HI),10-folds (10HI), 50-fold (50HI),100 folds (100HI)] of iodine excess and were fed for 3,6 and 12 months respectively. Serum levels of total T4(TT4), total T3(TT3), free T3(FT3), free T4(FT4), reverse T3 (rT3) and contents of T4, T3, rT3 in thyroid tissues were determined by RIA. Results Significant difference of TT4, FT4, TT3, FT3, rT3 levels in serum and T4, T3, rT3 contents in thyroid tissue between the groups was found when rats were fed for 3 to 6 months (F values were 54.07,67.80,15.51,27.71,19.73,61.51,40.67,53.86;58.80, 58.75,19.64,17.22,47.21,46.01,47.22,126.87,P<0.01). Statistical difference of T4, T3, rT3 contents in thyroid tissue between groups was also identified after rats were fed for 12 months (F values were 20.44,17.69,29.23,P < 0.01). Levels of thyroid hormones in serum and thyroid tissues from LI group were significantly lower than those in NI group, representing the status of hypothyroidism. The iodine excess groups demonstrated a tendency of hypothyroidism paralleling with the dosage of iodine intake as indicated by the decreasing of serum thyroid hormones and T3 values in thyroid tissues. Conclusions Long-term iodine deficiency and iodine excess can cause hypothyroidism in rats, which is obviously in iodine deficiency group. However, Wistar rats showed a strong tolerance to iodine excess for hypothyroidism only happened in the condition of a long-term of intervention of very high iodine excess (more than 50 folds of iodine intake).