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KMID : 1202020080010010039
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Journal of Korean Thyroid Association
2008 Volume.1 No. 1 p.39 ~ p.47
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Iodde Itself Regulates Iodide Uptake in Thyrocyte by Regulating sodium-iodide Symporter(NIS) Activity as Well as NIS Expression
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Park Young-Joo
Kim Ji-Eun
Chung June-Key
Kim Tae-Yong
Kim Won-Bae
Park Do-Joon
Cho Bo-Youn
Lee You-Jin
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Abstract
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Background and Objectives: Excess iodide ingestion causes the acute Wolff-Chaikoff effect, but the thyroid gland usually escapes this effect despite continued exposure to excess iodide. The purpose of this study was to determine the chronic effects of excess iodide and the underlying regulatory mechanisms.
Materials and Methods: The experiment was carried out on Adult male Sprague-Dawley rats. We injected iodide intraperitoneally and administered sodium iodide in a drinking water to observe acute and chronic effect of iodide, respectively.
Results: Thyroid hormone levels significantly decreased within the first 24 h and normalized within 3 d after iodide treatment in rats. The sodium-iodide symporter (NIS) mRNA and protein levels decreased slightly. Excess iodide decreased the symporter activity without concordant decrease of NIS mRNA or protein expression. Chronic ingestion of excess iodide decreased the NIS expression; the expression of the NIS mRNA recovered slightly despite continuous administration of iodide. The NIS activity was normal from 2 weeks after withdrawal of excessive iodide, while the protein levels remained low.
Conclusion: Our findings are consistent with the hypothesis that escape from the Wolff-Chaikoff effect occurs through down-regulation of NIS activity. Iodide seems likely to affect NIS expression by both transcriptional and post-transcriptional regulations, and appears to regulate the NIS activity not only by regulation of the NIS mRNA or protein expression, but also by some post-translational mechanisms.
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KEYWORD
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sodium-iodide, Symporter, Iodide, Thyroid
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