[Effects of short and long term immobilization stress on the functioning of Ca pump of the sarcoplasmic reticulum and cardiac resistance to Ca2+ excess].

In the experiments on rats a significant decrease of resistance to the contracture and arrhythmogenic effect of increased Ca2+ on the isolated hearts of animals after short term immobilization stress has been shown. After a long term stress (6 hours) the changes of the studied physiological parameters of the isolated hearts were not observed. Transport in the homogenates of the rat hearts was measured by the Ca--selective electrode on the ionometer ORION EA 940. After a 1-hour stress the rate of Ca--transport in sarcoplasmic reticulum (SR) substantially decreased as compared with the control (3.5 fold at 20 mcM), but at the higher concentration the Ca-transport was inhibited. The long term stress lead to a slower damage of functional Ca-transport system of SR--at 20 mcM the rate decreased by 25% as compared with control and at the higher concentration of Ca2+ depression of transport was not observed.