Regulation of the conductance and resting potential by extracellular K+ in frog taste receptor cells.
The effect of extracellular K+ on membrane currents was investigated by the patch clamp and fast perfusion techniques in frog (Rana temporaria) taste receptor cells (TRCs). When added to the bath, K+ increased the TRC conductance. The integral current and current fluctuations depended on the K+ concentration (2.5-90 mM) in the manner which suggested extracellular K+ to serve as a ligand activating ionic channels (potassium-activated (PA) channels). The influence of different ions on the PA current reversal potential indicated that the responsible channels are mainly permeable to K+ and H+. Relative permeabilities were estimated as P(H):P(K) = 3600:1. With 110 mM KCl in the patch pipette and 110 mM NaCl in the bath, isolated TRCs exhibited the resting potentials from -75 to -65 mV. When raised from 2.5 to 110 mM, extracellular K+ intensively depolarized TRCs. Membrane potential vs. K+ concentration displayed a slope of about 41 mV per logarithmic unit. This indicates that the K+ permeability of the TRC membrane dominates the other in setting the potential. With 10 mM K+ in the bath, the PA channels were the major contributor to setting the TRC resting potential. External K+ markedly increased the sensitivity of isolated TRCs to bath solution pH due to the activation of the PA channels suggesting their role in sour transduction.
Kolesnikov
S S
SS
Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region.
Bobkov YuV
D000818:Animals; D001464:Barium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002586:Cesium / Q000378:metabolism; D002713:Chlorine / Q000378:metabolism; D004594:Electrophysiology; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007477:Ions; D009532:Nickel / Q000378:metabolism; D011188:Potassium / Q000502:physiology*; D011898:Ranidae / Q000502:physiology*; D013650:Taste Buds / Q000502:physiology*
D007477:Ions; D002586:Cesium; D001464:Barium; D002713:Chlorine; D009532:Nickel; D006859:Hydrogen; D011188:Potassium