HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Corrigendum All Versions of this Article: 296/4/C654    most recent 00509.2008v1 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 Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Nicola, J. P. Articles by Carrasco, N. Search for Related Content PubMed PubMed Citation Articles by Nicola, J. P. Articles by Carrasco, N.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

The Na⁺/I^– symporter mediates active iodide uptake in the intestine

Departments of ¹Molecular Pharmacology and ²Neuroscience, Albert Einstein College of Medicine, Bronx, New York

Submitted 8 October 2008 ; accepted in final form 1 December 2008

Absorption of dietary iodide, presumably in the small intestine, is the first step in iodide (I^–) utilization. From the bloodstream, I^– is actively taken up via the Na⁺/I^– symporter (NIS) in the thyroid for thyroid hormone biosynthesis and in such other tissues as lactating breast, which supplies I^– to the newborn in the milk. The molecular basis for intestinal I^– absorption is unknown. We sought to determine whether I^– is actively accumulated by enterocytes and, if so, whether this process is mediated by NIS and regulated by I^– itself. NIS expression was localized exclusively at the apical surface of rat and mouse enterocytes. In vivo intestine-to-blood transport of pertechnetate, a NIS substrate, was sensitive to the NIS inhibitor perchlorate. Brush border membrane vesicles accumulated I^– in a sodium-dependent, perchlorate-sensitive manner with kinetic parameters similar to those of thyroid cells. NIS was expressed in intestinal epithelial cell line 6, and I^– uptake in these cells was also kinetically similar to that in thyrocytes. I^– downregulated NIS protein expression and its own NIS-mediated transport both in vitro and in vivo. We conclude that NIS is functionally expressed on the apical surface of enterocytes, where it mediates active I^– accumulation. Therefore, NIS is a significant and possibly central component of the I^– absorption system in the small intestine, a system of key importance for thyroid hormone biosynthesis and thus systemic intermediary metabolism.

dietary iodide absorption; active iodide transport; sodium/iodide symporter; enterocyte brush border