Measurement of calcium release from sarcoplasmic reticulum of skeletal muscle: effect of calcium and inositol 1,4,5-trisphosphate.

This chapter discusses the techniques for measuring Ca2+ release from isolated sarcoplasmic reticulum (SR) fractions and from the SR of skinned fibers. Morphologically, the SR consists of two distinct portions: (1) a network of longitudinal tubules (LSR) surrounding the myofibrils and (2) the terminal cisternae (TC), which form characteristic structures called “triads” with the invaginations of the plasma membrane, the transverse tubules (TT). The chapter illustrates the models for the study of Ca2+release. Ca2+ release can be studied using different approaches. One consists of the isolation and purification of the different organelles that are involved in this process and in the comparison of their biochemical characteristics. Because Ca2+ release channels are localized in the TC 6, it is mandatory to study Ca2+ fluxes in purified LSR and TC fractions. Skinned fiber is explained; it is composed of a segment of a fiber from which the barrier represented by the sarcolemma has been eliminated. This approach allows the investigator to precisely control the composition of the medium bathing the internal membranes and the contractile apparatus. The chapter also presents the techniques of measuring Ca2+ release. © 1987, Elsevier Inc.