[Work efficiency of the sarcoplasmic reticulum of the heart under normal and pathological conditions]

The problem concerning the participation of the sarcoplasmic reticulum in the relaxation of the heart muscle is discussed. It is concluded on the grounds of certain data that the system of the myocardial calcium pump includes several components, one of which, the Ca-dependent ATP-ase, is responsible for the accumulation of calcium ions while the others regulate this process accordingly. The results of an experiment with full extraction of the membrane Ca-transport system from the heart muscle are described, and the amount of sarcoplasmic reticulum in the pigeon myocardium is assessed.