1) The membrane potential of the newt red cell was measured with the intracellular microelectrode. The mean membrane potential was. 15.2±0.7mV (n=133, mean ± standard deviation of mean).
2) The membrane potential was almost linearly related (gradient: 1.2 mV/i0mM/L) to the concentration of Cl- of the external medium, but not to the logarithm of the changes in [Cl-]in/ [C1-]out as was expected from Nernst equation. The concentration of the external cations (Na+, K+, Ca++) had no effect on the membrane potential.
3) Oxygenation of the medium increased the membrane potential (-18.9 ± 0.7mV) whereas deoxygenation decreased it (-11.5 ± 0.3 mV).
4) The membrane potential depended on pH of the external medium. It decreased on the acid side (-11.7± 0.4mV at pH 5.7) and increased on the alkaline side (-19.9±1.2mV at pH 8.1).
5) As the temperature of the external Ringer solution was reduced from 18°C to 1°C, the membrane potential increased linearly at the ratio of 4.1 mV/10°C.
6) The origin of the red cell membrane potential and the role of this potential in the respiratory function were discussed.
