The K+-H+ Exchanger, Nigericin, Modulates Taste Cell pH and Chorda Tympani Taste Nerve Responses to Acidic Stimuli

Abstract

The relationship between acidic pH, taste cell pH(i), and chorda tympani (CT) nerve responses was investigated before and after incorporating the K(+)-H(+) exchanger, nigericin, in the apical membrane of taste cells. CT responses were recorded in anesthetized rats in vivo, and changes in pH(i) were monitored in polarized fungiform taste cells in vitro. Under control conditions, stimulating the tongue with 0.15 M potassium phosphate (KP) or 0.15 M sodium phosphate (NaP) buffers of pHs between 8.0 and 4.6, KP or NaP buffers did not elicit a CT response. Post-nigericin (500 × 10(-6) M), KP buffers, but not NaP buffers, induced CT responses at pHs ≤ 6.6. The effect of nigericin was reversed by the topical lingual application of carbonyl cyanide 3-chloro-phenylhydrazone, a protonophore. Post-nigericin (150 × 10(-6) M), KP buffers induced a greater decrease in taste cell pH(i) relative to NaP buffers and to NaP and KP buffers under control conditions. A decrease in pH(i) to about 6.9 induced by KP buffers was sufficient to elicit a CT response. The results suggest that facilitating apical H(+) entry via nigericin decreases taste cell pH(i) and demonstrates directly a strong correlation between pH(i) and the magnitude of the CT response.

Discovery of New Compounds Active against Plasmodium falciparum by High Throughput Screening of Microbial Natural Products

“…In the case of actinomycetes, antibiotics such as nigericins, oligomycins and actinomycins, among others, were identified. Nigericins are ionophores that catalyze the electroneutral exchange of K + for H + [ 29 ], whereas oligomycins and actinomycins act at the level of mitochondrial function and transcription, respectively [ 30 , 31 ]. Many of the known compounds identified are produced by species of the genus Streptomyces .…”

Effect of ENaC Modulators on Rat Neural Responses to NaCl

“…Table 1 also lists the different solutions containing specific activators and blockers that were applied to the tongue topically to effect changes in fungiform taste cell pH i , [Ca 2+ ] i , cAMP, cGMP and protein kinase A (PKA). Direct measurement on isolated polarized fungiform taste bud cells showed that pH i changes can be altered by varying the apical solution pH (pH o ), such that, a given change in pH o corresponded to a unique change in pH i [20] . In previous studies, the maximum increase in the Bz-sensitive NaCl CT response was obtained by stimulating the tongue with 100 mM NaCl solutions at pH 10.3 relative to pH 7.0 [11] .…”

pH-Responsive Graphene Oxide–DNA Nanosystem for Live Cell Imaging and Detection

“…This is a standard approach to calibrate pH ex vivo. 44,45 The pH response experiment was performed at 37 °C for 1 h, and then the resultant cells were investigated by LSCM. Figure 3A−C shows the results for HeLa cells.…”