[ C a2+]
. Frequency-dependent modulation of myoplasmic C a2+ transient. Voltage clamp protocol used is a 50 ms step pulse to 10 mV from a holding potential of -40 mV. (A) [ C a2+]
traces showing rate-dependent effects on systolic C a2+ concentration in the myoplasm for increasing stimulation frequencies from 0.5 Hz to 8.0 Hz. The inset shows the change in the maximum rate of rise and decay of the [ C a2+]
transient with stimulation frequency. (B) Frequency dependence of the maximum and minimum myoplasmic C a2+ concentration. (C) Bi-phasic rate dependence of EC coupling gain.