title: Umami changes intracellular Ca2+ levels using intracellular and extracellular sources in mouse taste receptor cells.
abstract: Recently, candidates for umami receptors have been identified in taste cells, but the precise transduction mechanisms of the downstream receptor remain unknown. To investigate how intracellular Ca(2+) increases in the umami transduction pathway, we measured changes in intracellular Ca(2+) levels in response to umami stimuli monosodium glutamate (MSG), IMP, and MSG + IMP in mouse taste receptor cells (TRCs) by Ca(2+) imaging. Even when extracellular Ca(2+) was absent, 1/3 of umami-responsive TRCs exhibited increased intracellular Ca(2+) levels. When intracellular Ca(2+) was depleted, half of the TRCs retained their response to umami. These results suggest that umami-responsive TRCs increase their intracellular Ca(2+) levels through two pathways: by releasing Ca(2+) from intracellular stores and by an influx of Ca(2+) from extracellular sources. We conclude that the Ca(2+) influx from extracellular source might play an important role in the synergistic effect between MSG and IMP.
authors.affiliation: Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Narukawa
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Mori
authors.forename: Yukako
authors.initials: Y
authors.lastname: Hayashi
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005260:Female; D007291:Inosine Monophosphate / Q000378:metabolism; D051379:Mice; D012970:Sodium Glutamate / Q000378:metabolism; D013649:Taste; D013650:Taste Buds / Q000378:metabolism*
chemical_list: D007291:Inosine Monophosphate; D002118:Calcium; D012970:Sodium Glutamate