[The effects of low temperature and extracellular ions on the membrane potential of newt red cells].

The membrane potential of the newt red cell was measured with a microelectrode to investigate the relation to its respiratory function. The membrane potential hyperpolarized with increasing oxygen density of the medium (pO2 0%; -13.4 +/- 0.4 mV, 21%; -16.2 +/- 0.4 mV, 100%; -18.9 +/- 0.7 mV) (mean +/- standard deviation of mean). As the temperature was reduced, the red cell membrane potential increased linearly, either in the completely oxygenated or in the deoxygenated medium. These two regression lines were almost parallel to that in the control medium (pO2 21%). At 0 degrees C, a) the membrane potential changed linearly to the Cl- concentration of the external medium, similarly in the case of that at room temperature. But its gradient was 0.3mV/10 mM, whereas 1.2mV/10 mM at 18 degrees C. b) The changes in the concentration of the external Na+ and Ca++ were not so remarkable on the membrane potential. c) Increase of the external K+ had a tendency to reduce the membrane potential.