Effect of excessive iodine intake on the 99Tcm-pertechnetate uptake function of thyroid and the related mechanism / 中华核医学与分子影像杂志

ABSTRACT

Objective To study the influence of excessive iodine intake on the 99Tcm-pertechnetate uptake function of thyroid and explore the related mechanism.Methods A total of 150 male Wistar rats were divided into normal iodine group (NI group) and 4 high iodine (HI) groups (10HI,50HI,100HI and 500HI group) with completely random method.Each group included 30 rats.Rats in HI groups were intragastrically administrated with different concentrations of KIO3,and rats in NI group were administrated with the same amount of distilled water.After a 7 d HI diet,each group was randomly divided into 3 subgroups7 d group (HI diet for 7 d),10 d group (HI diet for 7 d + limiting iodine for 3 d) and 14 d group (HI diet for 7 d + limiting iodine for 7 d).All rats were given 1.85 MBq 99TcmO4-,then the thyroid glands were isolated and weighed 20 min post-injection.The radioactive counts were measured and the thyroid uptake percentage activity of injected dose per gram of tissue (％ID/g) of 99TcmO4-for each sample was calculated.Sodium-iodide symporter (NIS) expression level was analyzed by Western blot.One-way analysis of variance or Welch test was used to compare the differences among groups,and Spearman rank correlation analysis was also used.Results At the same observation time,the ％ID/g of 99TcmO4-and NIS expression among different HI groups were statistically significant (F values48.825-119.219,all P＜0.01).In NI and 10 HI groups,％ID/g of 99TcmO4-and NIS expression were not significantly different among different time subgroups (F values0.090-4.753,all P＞0.05).Significant differences of ％ ID/g of 99TcmO4-and NIS expression were found among different time subgroups in 50HI,100HI and 500HI groups (F values10.442-90.408,all P＜0.01).Spearman correlation analysis showed that the concentration of iodine correlated negatively with ％ID/g of 99TcmO4-and NIS expression (rs values-0.853 and-0.950,both P＜0.01),while the ％ID/g of 99TcmO4-and NIS expression was positively correlated (rs =0.925,P＜0.01).Conclusions Excessive iodine intake can inhibit thyroid uptake of 99TcmO4-in rats,which is associated with the down-regulation of NIS expression.The degree of inhibition correlates positively with iodine concentration,and correlates negatively with NIS expression.The degree of recovery of NIS and ％ID/g of 99TcmO4-may relate to the time of limiting the iodine intake.