Ionic basis of resting membrane potential in frog taste cells.

Intracellular recording of the resting membrane potential was made from taste cells of the bullfrog by replacing the interstitial fluid surrounding the cells by various physiological saline solutions. The resting potential of the taste cell was -28 +/- 4 mV (mean +/- S.E.) after replacement of the interstitial fluid by normal Ringer solution. The resting potential was very much dependent on the interstitial K+ concentration ([K+]). Tenfold increase in [K+]o decreased the resting potential by 18 mV. Total removal of interstitial Na+ increased the resting potential by 40%. Ouabain in a concentration of 0.5 nM decreased the resting potential by 36% possibly due to inhibition of the Na+-K+ exchange pump. Neither total removal nor fourfold increase of interstitial Ca2+ changed the resting potential. Complete elimination of interstitial Cl- did not change the resting potential. The mean permeability ratio PNa/PK was calculated to be 0.41. It is concluded that the resting potential of a frog taste cell consists of ionic and metabolic components, and that the ionic component is due to the permeability of the cell membrane to K+ and Na+.