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This Article Full Text Full Text (PDF) All Versions of this Article: 296/5/G971    most recent 90514.2008v1 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 Google Scholar Google Scholar Articles by Kaji, I. Articles by Kuwahara, A. Search for Related Content PubMed PubMed Citation Articles by Kaji, I. Articles by Kuwahara, A.

HORMONES AND SIGNALING

Secretory effects of a luminal bitter tastant and expressions of bitter taste receptors, T2Rs, in the human and rat large intestine

¹Laboratory of Physiology, Graduate School of Nutrition and Environmental Sciences, Institute for Environmental Science, University of Shizuoka, and ²Shizuoka Saiseikai General Hospital, Shizuoka, Japan

Submitted 15 August 2008 ; accepted in final form 28 January 2009

Taste transduction molecules, such as G_gust, and taste receptor families for bitter [taste receptor type 2 (T2R)], sweet, and umami, have previously been identified in taste buds and the gastrointestinal (GI) tract; however, their physiological functions in GI tissues are still unclear. Here, we investigated the physiological function and expression of T2R in human and rat large intestine using various physiological and molecular biological techniques. To study the physiological function of T2R, the effect of a bitter compound, 6-n-propyl-2-thiouracil (6-PTU), on transepithelial ion transport was investigated using the Ussing chamber technique. In mucosal-submucosal preparations, mucosal 6-PTU evoked Cl^– and HCO₃^– secretions in a concentration-dependent manner. In rat middle colon, levels of 6-PTU-evoked anion secretion were higher than in distal colon, but there was no such difference in human large intestine. The response to 6-PTU was greatly reduced by piroxicam, but not by tetrodotoxin. Additionally, prostaglandin E₂ concentration-dependently potentiated the response to 6-PTU. Transcripts of multiple T2Rs (putative 6-PTU receptors) were detected in both human and rat colonic mucosa by RT-PCR. In conclusion, these results suggest that the T2R ligand, 6-PTU, evokes anion secretion, and such response is regulated by prostaglandins. This luminal bitter sensing mechanism may be important for host defense in the GI tract.

intestinal chemosensing; taste receptor type 2; prostaglandin E₂; transepithelial ion transport; 6-n-propyl-2-thiouracil