Effects of iodine excess on TPO and NIS genes mRNA expression in rats / 中国地方病学杂志

ABSTRACT

Objective To observe the effects of iodine excess on thyroid morphology,the expression of thyroid peroxidase and sodium iodide symporter mRNA and to explore their mechanisms.Methods One-month SD rats were divided into three groupscontrol iodine(CI),high iodine Ⅰ(HI Ⅰ)and high iodineⅡ(HI Ⅱ)and were fed with water containing iodine in different concentrations by adding K103(5,5000,10 000μg/L)respectively.Rats were sacrificed after being fed for six months.The morphology of thyroid was investigated under light microscopy and electron microscopy,the serum thyroid hormones and ratio of TPO/β-actin and NIS/β-actin were measured by radio-immunoassay and RT-PCR method.Results The major changes were increased follicles with colloid accumulation in HI groups.The levels of serum thyroid hormones TT3 and TT4 were decreased gradually from CI[(75.68±13.99,1.45±0.49)nmol/L]to HI Ⅰ[(73.82±16.48,1.34±0.31)nmol/L]and HIⅡ groups[(70.65±11.43,1.15±0.39)nmol/L],but there were no significant differences among three groups(F=O.371,l.163,P＞0.05).The TPO and NIS mRNA expressions in HI Ⅰ(1.28±0.10,0.56±O.17)and HI Ⅱ(1.14±0.04,0.39±0.06)were significantly lower(F=30.863,62.62.675,P＜O.05)than those of control group(1.39±0.08,0.71±0.13).Conclusions Chronic iodine excess leads to definite histological changes in rat thyroid,and inhibits the expressions of TPO and NIS mRNA as well as thyroid hormone synthesis,which in turn acts as a protective mechanism against iodine excess.