DIFFERENCES IN SENSITIVITY TO CA ION LACK BETWEEN MYOBLASTS AND LARGE MYOTUBES FROM CHICKEN BREAST MUSCLE

Large myotubes degenerated in Ca-deficient medium containing Mg ion. Numerous vacuoles appeared in the cytoplasm and then grew larger. The cells were disrupted and eventually detached from the culture dish. The time course of the destruction process differed from cell to cell and the rate of reduction of creatine kinase in the culture dish was constant irrespective of the time after the removal of Ca ion. Most of the myoblasts survived in Ca-deficient medium, after almost all the large myotubes had disappeared. These myoblasts fused to form new myotubes when Ca ion was supplied. Myotubes formed from myoblasts which had been cultured with Ca-deficient medium for 2 weeks also degenerated on Ca removal. Sr ion added to Ca-deficient medium did not completely prevent the destruction of myotubes but decreased the rate of their reduction.