Changes in outward K+ currents in response to two types of sweeteners in sweet taste transduction of gerbil taste cells.
Using the whole cell patch clamp technique, we measured changes in outward K+ currents of gerbil taste cells in response to different kinds of sweeteners. Outward K+ currents of the taste cell induced by depolarizing pulses were suppressed by sweet stimuli such as 10 mM Na-saccharin. The membrane-permeable analog of cAMP, cpt-cAMP, also decreased outward K+ currents. On the other hand, the K+ currents were enhanced by amino acid sweeteners such as 10 mM D-tryptophan. The outward K+ current was enhanced by external application of Ca(2+)-transporting ionophore, 5 microM ionomycin, and intracellular application of 5 microM inositol-1,4,5-trisphosphate (IP3). The outward K+ currents were no longer suppressed by 10 mM Na-saccharin containing 20 microM gurmarin, but were still enhanced by 10 mM D-tryptophan containing 20 microM gurmarin. These results suggest that sweet taste transduction for one group of sweeteners such as Na-saccharin in gerbils is concerned with an increase of the intracellular cAMP level, and that the transduction for the other group of sweeteners such as D-tryptophan is concerned with an increase of the intracellular IP3 level which releases Ca2+ from the internal stores.
Uchida
Y
Y
Department of Physiology, Nagasaki University School of Dentistry, Japan.
Sato
T
T
D000818:Animals; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D005849:Gerbillinae; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D010940:Plant Proteins / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism; D012439:Saccharin / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013549:Sweetening Agents / Q000494:pharmacology*; D013649:Taste / Q000187:drug effects / Q000502:physiology*; D013650:Taste Buds / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D014364:Tryptophan / Q000494:pharmacology
D007476:Ionophores; D010940:Plant Proteins; D015221:Potassium Channels; D013549:Sweetening Agents; C075206:Gurmarin protein, Gymnema sylvestre; D015759:Ionomycin; D015544:Inositol 1,4,5-Trisphosphate; D014364:Tryptophan; D000242:Cyclic AMP; D012439:Saccharin; D002118:Calcium