山梨医科大学雑誌　第4巻1号　021-028(1989)

The Inhibitory Effect of Iodide on TSH-stimulated Growth
of Cultured Rat Thyroid Cells (FRTL-5)

Fumito Akasu, Kazunaga Takazawa, Toyoshi Endo,
and Toshimasa Onaya

Abstract: We studied the inhibitory effect of iodide on thyroid growth in FRTL-5 cells, which preserve many thyroid functions. When the amount of iodide in medium exceeds 10^-6 M, TSH-stimulated [3H]thymidine incorporation into DNA was significantly inhibited. Methimazole (0.5 mM) reversed the suppression, as was observed in other functions such as thyroid hormone synthesis and secretion. Cell numbers were also monitored to ensure that [3H]thymidine incorporation reflected cell multiplication. Iodide inhibited TSH-stimulated cAMP formation and also 8-bromo-cAMP stimulated-[3H]thymidine incorporation into FRTL-5 cells, indicating that it acts on steps both before and after the formation of cAMP. The data demonstrated an autoregulatory role of iodide on the growth of FRTL-5 cells.

Key words: FRTL-5, iodide metabolism, thymidine incorporation, thyroid, cAMP




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