Abstract
Background: Administration of diagnostic activities of 131I, performed in order to detect thyroid remnants after surgery and/or thyroid cancer recurrence/metastases, may lead to reduction of iodine uptake. This phenomenon is called “thyroid stunning”. We estimated radiation absorbed dose-dependent changes in genetic material, in particular in sodium iodide symporter (NIS) gene promoter, and NIS protein level in human thyrocytes (HT). Materials and Methods: We used unmodified HT isolated from patients subjected to thyroidectomy exposed to 131I in culture. The different 131I activities applied were calculated to result in absorbed doses of 5, 10, and 20 Gy. Results: According to flow cytometry analysis and comet assay, 131I did not influence the HT viability in culture. Temporary increase of 8-oxo-dG concentration in HT directly after 24 h (p < 0.05) and increase in the number of AP-sites 72 h after termination of exposition to 20 Gy dose (p < 0.0001) were observed. The signs of dose-dependent DNA damage were not associated with essential changes in the NIS expression on mRNA and protein levels. Conclusions: Our observation constitutes a first attempt to evaluate the effect of the absorbed dose of 131I on HT. The results have not confirmed the theory that the “thyroid stunning” reduces the NIS protein synthesis.
Highlights
Thyroid cancer accounts for around 1% of all malignancies [1]
Multiple parameters were assessed in thyrocytes exposed to 131I in culture, in order to get insight into possible cellular and molecular mechanisms underlying the stunning phenomenon
We did not observe any influence of the applied absorbed doses of 131I on the rate of apoptosis and necrosis of thyrocytes in vitro (Figure 1)
Summary
Thyroid cancer accounts for around 1% of all malignancies [1]. Diagnostic whole body scan (DxWBS) with radioiodine 131I, performed in order to detect thyroid tissue remaining after surgery and/or thyroid cancer metastases, belongs to the main elements of follow up examination in patients thyroidectomized due to the differentiated thyroid cancer (DTC) [2]. It is suggested that in some cases, administration of a diagnostic activity of radioiodine may lead to reduction of iodine uptake by remaining normal thyroid or DTC cells during the post-therapy whole body scan (RxWBS). Administration of diagnostic activities of 131I, performed in order to detect thyroid remnants after surgery and/or thyroid cancer recurrence/metastases, may lead to reduction of iodine uptake. Results: According to flow cytometry analysis and comet assay, 131I did not influence the HT viability in culture
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