Effect of five taste ligands on the release of CCK from an enteroendocrinecell line, STC-1

Here, we investigated which taste ligand induces the CCK (cholecystokinin) release from intestinalSTC-1 cells. We first developed a new assay to measure the release of CCK. The expressionvector for CCK type A receptor (CCKAR) was permanently introduced into HEK293T cells and acell line was established (CCKAR/HEK). Then, STC-1 cells were treated with taste ligands andthe incubated buffer of STC-1 cells containing released CCK was applied to CCKAR/HEK cells.Since CCKAR couples to Gq-signaling, the CCK-induced receptor activation can be monitored bythe method of Ca2+ -imaging. Therefore, when CCK is released from STC-1 cells to culture mediumwith taste stimulation, Ca2+ activation of CCKAR/HEK should be observed. Among five differenttaste ligands (saccharin, Na-glutamate, NaCl, denatonium benzoate, HCl), only denatoniumbenzoate and HCl induced the release of CCK in STC-1 cells. Thus, we found that only specifictaste ligands induce the CCK release, and that other three taste ligands cannot induce the releaseof CCK despite of their ability to elevate the intracellular Ca2+ level in STC-1 cells.