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This Article Full Text Full Text (PDF) All Versions of this Article: 294/4/E802    most recent 00013.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Tran, N. Articles by Hershman, J. M. PubMed PubMed Citation Articles by Tran, N. Articles by Hershman, J. M.

Thyroid-stimulating hormone increases active transport of perchlorate into thyroid cells

Endocrine Research Laboratory, Veterans Affairs Medical Center West Los Angeles, University of California Los Angeles School of Medicine, Los Angeles, California; and National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia

Submitted 7 January 2008 ; accepted in final form 24 February 2008

Perchlorate blocks thyroidal iodide transport in a dose-dependent manner. The human sodium/iodide symporter (NIS) has a 30-fold higher affinity for perchlorate than for iodide. However, active transport of perchlorate into thyroid cells has not previously been demonstrated by direct measurement techniques. To demonstrate intracellular perchlorate accumulation, we incubated NIS-expressing FRTL-5 rat thyroid cells in various concentrations of perchlorate, and we used a sensitive ion chromatography tandem mass spectrometry method to measure perchlorate accumulation in the cells. Perchlorate caused a dose-related inhibition of 125-iodide uptake at 1–10 µM. The perchlorate content from cell lysate was analyzed, showing a higher amount of perchlorate in cells that were incubated in medium with higher perchlorate concentration. Thyroid-stimulating hormone increased perchlorate uptake in a dose-related manner, thus supporting the hypothesis that perchlorate is actively transported into thyroid cells. Incubation with nonradiolabeled iodide led to a dose-related reduction of intracellular accumulation of perchlorate. To determine potential toxicity of perchlorate, the cells were incubated in 1 nM to 100 µM perchlorate and cell proliferation was measured. Even the highest concentration of perchlorate (100 µM) did not inhibit cell proliferation after 72 h of incubation. In conclusion, perchlorate is actively transported into thyroid cells and does not inhibit cell proliferation.

iodide; Na⁺/I^– symporter