Calcium release from the sarcoplasmic reticulum

Abstract

This review suggests that Ca2+ release from the sarcoplasmic reticulum (SR) is initiated by two different processes in mammalian cardiac muscle and predominantly fast skeletal muscle. In mammalian cardiac muscle, the Ca2+ that crosses the surface membrane during the action potential could initiate Ca2+ release from the SR. In contrast, Ca2+ release from the SR of fast skeletal muscle could be initiated by the depolarization of the transverse tubules through a process about which the only well established finding is that it does require Ca2+. It would be interesting to see whether other types of muscles, such as slow skeletal muscles or some smooth muscles, use a combination of both processes in variable proportions. Such a combination is not yet excluded for any type of muscle. The suggestion that there is a difference between cardiac and fast skeletal muscles in the process of Ca2+ release from the SR concerns only the initiation of this release.