[Stress-induced changes in the functioning of the Ca-transport system of the cardiac sarcoplasmic reticulum and its resistance to endogenous damaging factors].

The kinetic characteristics of a calcium transport by sarcoplasmic reticulum was measured in homogenate of rat heart by means of Ca-selective electrode in the presence of oxalte and azide. As a function of the increasing CaCl2 concentration, the rate of Ca2+ uptake demonstrate a linear (in the physiological concentration field) and saturable components. Prolonged immobilization was accompanied by a decrease in Ca-concentration dependence of Ca2+ uptake. Nonsignificant fall of Vm was accompanied by simultaneous decrease of KM by 30% after stress. Storage of heart homogenates revealed three-fold decrease of inactivation rate in the stress series. Initial concentration of free Ca2+ and its raise during storage was increased in heart homogenates, prepared after stress. The role of calcium pump resistance to endogenous damage factors in the stress-induced heart disturbance are discussed.