| Purpose: To study the regulation mechanism of iodine-rich herbal decoction to thyroid hormones metabolism of peripheral tissues in iodine-deficiency induced autoimmune thyroiditis susceptible individuals by comparing the effect of iodine-rich herbal decoction and iodine excess on the expression of type Ⅱ iodothyronine deiodinase(D2)and type Ⅲ iodothyronine deiodinase(D3) m RNA in the hearts and kidneys of iodine-deficiency NOD.H-2h4 mice.Material and method: 8-week-old NOD.H-2h4 female mice were made model of susceptible autoimmune thyroiditis and goiter caused by iodine deficiency by feeding a low iodine diet and double distilled water with 90 days,divided into four groups randomly:the normal control group(NC),the low iodine group(LI),the iodine excess group(IE)(the IE group is made of potassium iodate with the iodine concentration of 1900μg/L) and the iodine-rich herbal decoction group(HIE)(The HIE group include Haizao 15 g, Kunbu 15 g, Haidai 7.5g with the iodine concentration of 1900.36μg/L.Intragastric dose is calculated according to human and mouse body surface area, Crude drug content of 4.7 g/(Kg·d)). The mice were killed after 90 days.The levels of serum total triiodothyronine(TT3) and total thyroxine(TT4),tissue levels of T3 and T4 were measured by Radio immunoassay(RIA) method.Meanwhile the mice serum thyroid stimulating hormone(TSH)were measured by immunoradiometric assay(IRMA).D2 m RNA and D3 m RNA expression levels in the hearts and kidneys of NOD.H-2h4 mice were determined by RT-PCR method.Results: 1.Thyroid function in mice:After treatment by different factors for 90 days,In the normal control group, the serum levels of TT3(2.24±0.54nmol/L), TT4(90.86 ±9.35nmol/L), TSH(1.14±0.23 m UI/L); in the low iodine group, the serum levels of TT3(2.36±0.72nmol/L), TT4(167.68±68.74nmol/L), TSH(1.33±0.13 m UI/L). In the iodine excess group, the serum levels of TT3(2.44±0.85nmol/L), TT4(117.79±21.98nmol/L), TSH(1.33±0.07 m UI/L); in the iodine-rich herbal decoction group, the serum levels of TT3(3.35±0.54nmol/L), TT4(130.46±42.85nmol/L), TSH(1.24±0.25 m UI/L),there was not obvious difference among every group on serum TT3,TT4 and TSH(P﹥0.05). 2.The light microscope of thyroid tissue morphology :the normal control group : follicular cavities were round or oval with medium size, follicular epithelial cells were cuboidal and follicular cavities filled with gelatinous rich and uniform.There were two mice spontaneous thyroiditis with minor inflammatory cells; the low iodine group: the size of follicular cavity was different, numbers of follicular polymerization for giant follicular form.The intercellular substance between follicular epithelial cells was little, follicular epithelial deformed by extrusion,follicular cavities filled with pink colloid, 0/10 mice occurred thyroiditis; the iodine excess group : follicular cavities increased generally, follicular epithelial cells deformed by extrusion, follicular cavities filled with gelatinous.With treatment factor for 90 days mice occurred thyroiditis except 1 mice(9/10),parts of follicular structure atrophy and destroyed as lymphocytes infiltration,the inflammatory cell infiltration area accounted for the total area of about 30%-50%; the iodine-rich herbal decoction group: Follicular cavities increased partly.Follicular cavities filled with gelatinous.Only three mice occurred thyroiditis with the treatment factor(3/10). The area of inflammatory cell infiltrates was small and the part of follicular structure by no lymphocytic infiltration was completed. The prevalence of autoimmune thyroiditis:in the NC group,the MC group,the IE group and the HIE group was respectively 2/10,0/10,9/10 and 3/10. 3.RT-PCR: Compared with the NC group(1.02±0.25),the expression of D2 m RNA in the hearts was significantly increased in the MC group(1.76±0.34)(P﹤0.01) and comparing with the HIE group(0.76±0.32),the expression of the IE group(1.42±0.33)was obviously increased(P﹤0.05).In the kidneys,the D2 m RNA levels in the IE group(4.07±0.88)was significantly increase higher than that in the HIE group(1.91±0.62)(P<0.01).Compared with the NC group(1.19±0.73),the expression of D3 m RNA in the kidneys was significantly increased in the IE group(2.19±0.56)(P﹤0.05),and shows an up trend of HIE group(1.52±0.44),but has not obvious difference.(P >0.05)。Conclusion: 1.In the iodine excess mice, expression of renal D2 m RNA, D3 m RNA increases significantly.Compared with D3 m RNA,the expression of D2 m RNA shows the up trend.With the action of D2 in the peripheral tissues, T4 transforms to the high activity of T3, increasing the risk of iodine induced hyperthyroidism. 2.In the iodine-rich herbal decoction by the same iodine content, among the heart and kidney tissues of mice, a little increasing expression of D2 m RNA, D3 m RNA is observed in mouse kidney.Compared with the iodine excess,the iodine-rich herbal decoction reduces the risk of iodine induced hyperthyroidism.
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