Proton currents through amiloride-sensitive Na+ channels in isolated hamster taste cells: enhancement by vasopressin and cAMP.
Amiloride has been suggested to inhibit responses to a variety of taste stimuli, including salty, sweet, and sour (acid). To test for the involvement of amiloride-sensitive Na+ channels in the transduction of acid stimuli, fungiform taste receptor cells were examined using patch-clamp techniques. Approximately one-half of all cells had amiloride-sensitive Na+ currents (INa) with a Ki value near 0.2 microM amiloride. After blocking voltage-gated conductances, cells having amiloride sensitivity were tested for responses to acid stimuli. Over three-fourths of cells showed an inward proton current (IH+) with an extrapolated reversal potential near approximately +150 mV, which was completely blocked by amiloride (30 microM). Treatment of isolated taste cells with arginine8-vasopressin caused equivalent increases in both INa and IH+; each effect was mimicked by 8-Br-cAMP. Taken together, these results indicate that protons permeate amiloride-sensitive Na+ channels in hamster fungiform taste cells and contribute to acid transduction.
Gilbertson
T A
TA
Department of Anatomy and Neurobiology, Colorado State University, Fort Collins 80523.
Roper
S D
SD
Kinnamon
S C
SC
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D006224:Cricetinae; D000242:Cyclic AMP / Q000494:pharmacology*; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D011522:Protons; D015398:Signal Transduction; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013650:Taste Buds / Q000502:physiology*; D014667:Vasopressins / Q000494:pharmacology*
D011522:Protons; D015222:Sodium Channels; D014667:Vasopressins; D001127:Arginine Vasopressin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000584:Amiloride; D000242:Cyclic AMP