Localization of phosphatidylinositol signaling components in rat taste cells: Role in bitter taste transduction

To assess the role of phosphatidylinositol turnover in taste transduction we have visualized, in rat tongue, ATP-dependent endoplasmic reticular accumulation of ⁴⁵Ca²⁺, inositol 1,4,5-trisphosphate receptor binding sites, and phosphatidylinositol turnover monitored by autoradiography of [³H]cytidine diphosphate diacylglycerol formed from [³H]cytidine. Accumulated ⁴⁵Ca²⁺, inositol 1,4,5-trisphosphate receptors, and phosphatidylinositol turnover are selectively localized to apical areas of the taste buds of circumvallate papillae, which are associated with bitter taste. Further evidence for a role of phosphatidylinositol turnover in bitter taste is our observation of a rapid, selective increase in mass levels of inositol 1,4,5-trisphosphate elicited by low concentrations of denatonium, a potently bitter tastant.