Radiocalcium Release by Stimulated and Potassium-Treated Sartorius Muscles of the Frog

Abstract

Stimulation of frog (Rana pipiens) sartorius muscle accelerates release of Ca⁴⁵, but only during the period of stimulation. No appreciable difference is obtained in the calcium released per impulse whether stimulation is at a rate of 20/sec. or 0.5/sec. However, prior stimulation may appreciably increase the loss per impulse. In unfatigued muscles, the minimum amount of calcium liberated during an isotonic twitch is estimated to be about that previously calculated to enter, viz. 0.2 µµmole/cm².