| Research Abstract |
Factors modulating thyroid cell growth were studied using porcine, human and rat thyroid cells.
1. Basic fibroblast growth factor (FGF) dose-dependently stimulated DNA synthesis and proliferation of porcine thyroid cells and rat thyroid cell line (FRTL-5) cells. On the other hand, FGF inhibited TSH-induced iodine metabolism and expression of TPO (thyroid peroxidose) mgNA expression stimulated by TSH, Specific receptors and mRt4A of FGF were expressed in porcine thyroid cells, suggestion that FGF is an autocrine/paracrine factor regulating thyroid growth and function.
2. Endocthelin inhibited iodide uptake stimulated by either TSH or 8-Br-cAMP-in porcine thyroid cells. Although ET stimuated c-fos MRNA expression, it did not alter D14A synthesis in porcine thyroid cells. However, it enhanced DNA synhthesis stimulated by IGF-I in FRTL-5. In contrast, ET inhibited TSH-stimulated DNA synthesis in CAMP independent manner. Messenger RNA of ET was found in porcine thyroid cells. Thus, it appears that endothelin is involved in thyroid cell growth.
3. Retinoid was able to Potentiate growth promoting activity of IGF-I and EGF, and was an inhibitor to iodine metabolism stimulated by TSH or 8-Br-cAMP. Retinoid could be useful in treatment of hyperthyroidism.
4. Iodide inhibited, but lithium enhanced mitogenic activity of IGF-I and EGF in porcine thyroid cells in culture.
5. In human thyroid papillary carcinoma, the number of receptors for IGF-I and IGF-II was higher as comapred to that in normal thyroid tissues. Thus, a number of factors are involved in the regulation of thyroid cell growth.
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