[Effect of calcium on glycogen synthetase activity in skeletal muscles and myocardium of chick embryos and chickens].

The effect of calcium on the glycogensynthetase activity was studied in the skeletal muscles and myocardium of chick embryos and chickens. Under in vitro conditions the effect of calcium on the enzymes in the myocardium is detected from the 12th day of embryonic development and is pronounced in a significant decrease of the activity in its both forms. The same effect in the skeletal muscles is observed only from the 16th day of embryonic life. In chickens calcium also causes a significant decrease in the activity of the two forms of glycogensynthetase both in skeletal muscles and myocardium. The effects of calcium found in the in vitro experiments are reproduced under in vivo conditions as well. The coincidence is established between the time of appearance of sensitivity of the glycogensynthetase system to calcium and formation of the Ca-transport function of sarcoplasmic reticulum in these muscles. Possible participation of calcium as an intermediary in realization of the cathecholamine action on the glycogensynthetase system is discussed.