[Role of calcium in the regulation of syncytial formation and the formation of creatine kinase during the development of muscle in the absence of creatine]

Abstract

1. It is demonstrated for the first time that typically elongated chick myotubes, with more than 20 nuclei per fiber and creatine kinase, appear in cultures fed all time with partially defined auto-conditioned medium. 2. It was found that the skeletal muscle enzyme of the chick embryo is independent of the presence of creatine and consequently is another constitutive enzyme like the creatine kinase of the early embryonic chick heart. 3. Calcium elicited the activity of the enzyme and promoted fusion of myoblasts in a creatine-free partially defined medium, in the absence of embryo extract. 4. It is suggested that creatine kinase is a dual molecule, working as an ATPasa in the absence of creatine with H2O as the nucleophilic reagent. 5. Alternatively, it is possible that creatine kinase can be synthesized and localized in advance to the advent of creatine in myocardial and skeletal muscle cells.