| Objectives: To study the changes of thymic epithelial cells (TECs) in Wistar rats given by various concentrations of iodine.Methods: Wistar rats, 1 month after stopping lactation, were divided into 6 groups and given by different concentrations of iodine (KI) which were Low iodine(LI), normal iodine(NI),5 fold high-iodine (5HI), 10 fold high-iodine (10HI),50 fold high-iodine (50HI),100 fold high-iodine (100HI). 3 months and 6 months later, the rats were sacrificed, the thymus were excised and weighed, stained with HE and immunohistochemistry , electron microscopic study . In this paper we focus on the description of thymic index, volume density(Vv)and numerical density on area (NA) of CK18+TEC, CK19+TEC, heterogeneity of TECs and their reactions to different concentrations iodine(thyroid hormone). Results:1. After treatment for 3 months, thmic index in 50HI, 100HI and LI groups were markedly lower than LI group; After treatment for 6 months, there was no diffenence between NI and experimental groups.2. Immunohistochemical study:three months later, the Vv and NA of CK18+TECs in 5HI group were lower than those of NI group, then increase gradually with increasing concentrations of KI and grow drastically (p<0. 01)in 100HI group. After treatment for 6 months, the Vv and NA of CK18+TECs in 10HI, 50HI, 100HI and LI groups were significantly increased compared with NI group, especially in 10HI group , it was the highest.Comparison with 3-month groups, the Vv and NA of CK18+TECs in corresponding 5HI 10HI 50HI and LI groups increased conspiciously (p<0.05) in 6-month groups, however there were no evident changes in NK 100HI groups. Concerning CK19+ TECs, no obvious changes were found after 3 months treatment, however 6 months later, the Vv and NA of the CK19+TECs in 50HI 100HI LI groups were lesser than NI group. CK19TEC in all corresponding groups were significantly increased in 6-month groups compared with those in 3-month groups.3. Thymic epithelial cells had four kinds of the changes on ultrastructure:l)Tonofilaments were significantly increased (Type 1 TECs in every experimental groups);2)Numerous dense lysosome -like granules(Type 6 TEC in 10HI); 3)Vacuolization (Types 1 and 6 TECs in 100HI); 4)Many low electron density vacuoles can be seen(Type 6 TEC in 10HI, Types 4 and 6 TECs in 50HI, Type 2 TEC in 100HI, Type 1 TEC in LI group);5)Degeneration of cell membrane (Types 1 and 6 TECs in 100HI group). Conclusions:l.TECs are heterogenous, with electron microscope. We prove that different locating TECs have various reactions to thyroid hormones.2. CK18 and CK19 are cytokeratins with small molecular weights, the CK18+ TECs were different with CK19+ TECs in origin . distributions and reactions to thyroid hormones.3.Thymocytes and thymic epithelial cells develop in finely balanced microenvironment. Intaking high concentration of iodine or iodinedeficiency can destroy the thymic microenvironment and injury both thyraocytes and thymic epithelial cells. |
