The effect of calcium ions on electrical properties of striated muscle fibres.

Abstract

1. The membrane potential of single striated muscle fibres of toad, as modified by various Ca concentrations in Ringer fluid, was measured by means of an intracellular microelectrode.2. The resting potential rose by up to about10mV with the increase of Ca concentration and it fell by several mV with the decrease in calcium to onefifth of the normal.3. The magnitude of the action potential became greater by both 10-fold.and 30-fold increases in Ca concentration, but became smaller by 68.3-fold increase and by its decrease. The reversed potential was reduced with both the increase and decrease in Ca concentration.4. Both the rate of rise and fall of the action potential was reduced approximately in proportion to the increase in Ca concentration, and the decrease in Ca concentration also caused a reduction in both values.5. The neagtive after-potential became more prominent both with increased Ca concentration and with the rise in temperature.6. The possible mechanism of the action of Ca ions on the active membrane was discussed.