Time course of activation of calcium release from sarcoplasmic reticulum in skeletal muscle

• Published in: Biophysical journal 1988-12, Vol.54 (6), p.1159-1163
• Main Authors: Simon, B.J., Schneider, M.F.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Calcium - metabolism; Cell physiology; Coloring Agents; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Kinetics; Membrane Potentials; Molecular and cellular biology; Muscles - physiology; Naphthalenesulfonates; Ranidae; Sarcoplasmic Reticulum - physiology; Time Factors
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1016/S0006-3495(88)83050-9

Myoplasmic free calcium transients were measured with antipyrylazo III in voltage clamped segments of frog skeletal muscle fibers and were used to calculate the rate of release (Rrel) of calcium from the sarcoplasmic reticulum. Intramembrane charge movement was measured for the same pulses in the same fibers. During a depolarizing pulse Rrel rose to an early peak and then decayed relatively rapidly but incompletely due to calcium-dependent inactivation (Schneider M.F., and B.J. Simon. 1988. J. Physiol. (Lond.). 405:727–745). Two approaches were used to determine release activation independent of the effects of inactivation: (a) a mathematical correction based on the assumption that inactivation was a process occurring in parallel with and independently of activation; (b) an experimental procedure in which release was maximally inactivated by a large short prepulse and then the remaining noninactivatable component of release was monitored during a subsequent test pulse. Both procedures gave the same time course of activation of release. Release activation paralleled the time course of intramembrane charge movement but was delayed by a few milliseconds.