The amount of thyroglobulin synthesized from thyroid cells and stored in colloid space is very important in thyroid hormone synthesis. The thyroglobulin synthesis is mainly regulated by TSH secreted from the pituitary gland, But recently there
were
some
reports about the possibility that iodine regulated the thyroid protein synthesis. So our studied were conducted to determined whether iodine could have inhibitory effect on thyroglobulin synthesis and methimazole could abolish the inhibitory
effect of
iodine.
Porcine thyroid cells were isolated by sequential trypsinization in the presence of GGTA, seeded at high density(1×106 cells/㎠) and cultured. One week later, Nal was added in different concentrations(10-7, 10-6, 10-5, 10-4M). 24hour medias were
collected and checked the amount of thyroglobulin secreted. And also pulse-labeling were performed with[35S] cysteine/methionine(1-2 uCi/well) for I hour at the same conditions. We used 3mM methimazole and 10-4M Nal to observe the blocking effect
of
methimazol to iodine.
The extracellular thyroglobulin secretion was significantly decreased by iodide in dose dependent manner(82.4%, 80.7%, 76.8% and 73.1% of control). And also intracellular thyroglobulin synthesis was significantly decreased by iodide in dose
dependent
manner(100.5%, 83.4%, 82.3% and 79.4% of control). The inhibitory effect of iodide was abolished by methimazole(74.7% to 101.3% of control).
These data indicate that high iodide inhibit the thyroglobulin synthesis and secretion from the thyroid cells, and furthermore autoregulation by iodide may include thyroglobulin synthesis. And also this effect is dependent on the generation of an
organic form of iodine because methimazole abolish the inhibitory effect of iodide. (J Kor Soc Endocrinol 9: 318-324 1994)
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