甲状腺激素对胸腺上皮细胞CK19蛋白表达的影响

目的探讨甲状腺激素对胸腺的发育的影响及可能的机制。方法将12只怀孕4d的大鼠随机分成A组和B组，A组正常饮水，B组孕鼠供以含有0．02％甲巯咪唑的饮水制备仔鼠甲状腺功能低下动物模型，将A组的仔鼠随机分成对照组和甲状腺素钠组，将B组的仔鼠随机分成甲低组和甲低＋甲状腺素钠组。甲状腺素钠组和甲低＋甲状腺素钠组于出生后15d给予腹腔注射甲状腺素钠（0．5mg／kg体重，1次／d），连续给药25d。所有动物于出生后40d麻醉处死，测定仔鼠的胸腺重量及脏器指数；采用放射免疫技术测定仔鼠血清中三碘甲状腺原氨酸（triiodothyronine，T3）、四碘甲状腺原氨酸（tetraiodothyronine，T4）、促甲状腺激素（thyroid—stimulating hormone，TSH）水平，免疫组织化学技术检测胸腺上皮细胞细胞角蛋白19（cytokeratin 19，CK19）蛋白的表达量。结果与对照组比较，甲状腺素钠组仔鼠血清中T3、T4显著升高，TSH减少，胸腺重量增大；甲低组仔鼠血清中T3、T4明显降低，TSH显著增高，胸腺重量降低，胸腺上皮细胞CK19蛋白表达减少。与甲低组比较，甲低＋甲状腺素钠组仔鼠血清中T3、T4升高，TSH降低，胸腺指数增大，胸腺上皮细胞CK19蛋白的表达明显增多。结论甲状腺激素可以通过影响胸腺上皮细胞CK19的表达量，使胸腺发育或退化。

EFFECT OF THYROID HORMONES ON EXPRESSION OF CK19 IN THYMIC EPITHELIAL CELLS

Objective To investigate the effect of different condition of thyroid hormones on thymic development and its possible mechanism. Methods Twelve rats at day 4 of gestation were divided into group A and group B. Group A was given normal water; Group B was fed with 0.02% methimazole. The filial rats of group A were divided into the control group and the levothyroxine sodium group, and those of group B were divided into the hypothyroid group and the hypothyroidlevothyroxine sodium group. The filial rats of postnatal day 15 in the levothyroxine sodium group and hypothyroidlevothyroxine sodium group were injected intraperitoneally with levothyroxine sodium （0.5mg/kg） once a day for 25 successive clays. The other groups were injected intraperitoneally with the same dose of normal saline. All the filial rats of postnatal day 40 were sacrificed under anesthesia. The thymic weight and index were measured, and triiodothyronine （T3）,tetraiodothyronine （T4） and thyroid-stimulating hormone （TSH） were determined by radioimmunity technique, and the expression of cytokeratinl9 （CK19） was detected with SP immunohistochemical method in thymic epithelial cell. Results Compared with those in the control group, the T3 and T4 values were significantly higher, and the TSH values were lower, and the weights of the thymus became larger in the levothyroxine sodium group. The T3 and T4 values were significantly lower, the TSH secretion was significantly higher, the weights of the thymus were reduced, and the expression of CK19 on the thymic epithelial cells was reduced in the hypothyroid group. Compared with those in the hypothyroid group, the T3 and T4 values were significantly higher, the TSH values were lower, and the thymus index increased, and the expression of the CK19 on the thymic epithelial cells was higher in the hypothyroid-levothyroxine sodium group. Conclusion The different conditions of thyroid hormones induced the development and involution of thymus by affecting the expression of CK19 in the thymic epithelial cells.