Measurement of calcium release from the sarcoplasmic reticulum into the myoplasm of frog cut muscle fibers

Abstract

Ca release from the sarcoplasmic reticulum of frog cut muscle fibers has been estimated with two different methods. The first method is to measure the myoplasmic free [Ca] transient under nonperturbing conditions and then estimate the amounts of Ca that are bound to the myoplasmic buffers troponin and parvalbumin. The Ca released from the sarcoplasmic reticulum is estimated from the sum of the concentrations of free Ca and of Ca bound to the indicator, to troponin, and to parvalbumin. The second method is to estimate the amount of Ca release by capturing most of the Ca with a large concentration of a high affinity Ca buffer. Both methods give similar estimates of the amount of Ca release following a single action potential and of the shape and amplitude of the release waveform.