The resting membrane potential of frog sartorius muscle.

1. The absolute resting membrane potential of the frog sartorius muscle was determined in Ringer solution at 20 degrees C. 2. Membrane potentials were measured with 0.03, 0.1, 0.3, 1.0 and 3.0 M-KCl electrodes; potentials, including the micro-electrode-tip potentials, were -62.4, -75.7, -83.0, -87.7 and -90.7 mV respectively. 3. Membrane potentials were corrected for the liquid junction potentials between the Ringer and KCl solutions, and the myoplasm and the KCl solutions of the micro-electrodes, using the Henderson's liquid junction equation. 4. The cation (U) and anion (V) conductances of the myoplasm were adjusted to give a constant membrane potential after correction for liquid junction potentials. The final values for U and V were 5.6 and 1.3 mmho/cm respectively, resulting in a membrane potential of -93.0 mV. 5. The correction for the liquid junction potential was -2.6 mV when a 3 M-KCl micro-electrode was used.