2011 Volume 73 Issue 4+5 Pages 177-185
Recent studies have demonstrated that taste receptors, T1Rs and T2Rs, are expressed not only in taste buds but also in the gut. In the duodenum, it is thought that the secretion of secretin (S cells) and somatostatin (D cells) is stimulated by acid, that gastrin (G cells) and cholecystokinin (CCK) (I cells) are stimulated by proteins and amino acids, and that serotonin (EC cells) scretion is triggerd by mechanical stimulation sensing gut endocrine cells. We examined the expression of T1R3 in the duodenum by reverse transcription polymerase chain reaction (RTPCR) and in situ hybridization. Double-label studies showed that approximately 50% of secretin positive cells (S cells) were coexpressed with T1R3, and approximately 33% of AADC positive cells (EC cells) were coexpressed with T1R3. On the other hand, T1R3 never colocalized with somatostatin (D cells), gastrin (G cells), or CCK (I cells). These results suggest that S cells may regulate the secretion of secretin, stimulated not only by acid but also by sweet substances and/or amino acids. Similarly, EC cells may regulate the secretion of serotonin by stimuli other than a mechanical one.
