Role of apical ion channels in sour taste transduction.
Sour taste perception depends primarily on the concentration of H+ in the taste stimulus. Acid stimuli elicit concentration-dependent action potentials in taste cells. Recent patch-clamp studies suggest that protons depolarize taste cells by direct interaction with apically located ion channels. In Necturus maculosus, the voltage-dependent K+ conductance is restricted to the apical membrane of taste cells. The current flows through a variety of K+ channels with unitary conductances ranging from 30 to 175 pS, all of which are blocked directly by citric acid applied to outside-out or perfused cell-attached patches. In contrast, hamster fungiform taste cells appear to utilize the amiloride-sensitive Na+ channel for acid transduction. Amiloride completely inhibits H+ currents elicited by acid stimuli in isolated taste cells, with an inhibition constant similar to that for amiloride-sensitive Na+ currents (Ki = 0.2 microM). Treatment of isolated taste cells with the bioactive peptide arginine-vasopressin results in similar increases in both the amiloride-sensitive Na+ and H+ currents; the effect is mimicked by 8-bromocyclic AMP. These results suggest that H+ can permeate amiloride-sensitive Na+ channels in hamster fungiform taste cells, contributing to the transduction of sour stimuli.
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Department of Anatomy and Neurobiology, Colorado State University, Ft Collins 80523.
D000818:Animals; D006224:Cricetinae; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D009337:Necturus; D026902:Potassium Channel Blockers; D011522:Protons; D015398:Signal Transduction / Q000502:physiology*; D015222:Sodium Channels / Q000187:drug effects; D013649:Taste / Q000502:physiology*
D007473:Ion Channels; D026902:Potassium Channel Blockers; D011522:Protons; D015222:Sodium Channels