Cell fusion and creatine kinase activity in cultures of chick embryo myoblasts

In primary cultures of myoblasts from embryonic chick skeletal muscle, cells undergo a period of proliferation lasting 2 days, and then fuse into multinucleated myotubes. It is a generally accepted idea that cell fusion represents a critical event followed by the synthesis of specific proteins. It was reported that no specific enzymes are synthesized by mononucleated myoblasts (COLEMANan d CoLEhiAN, 1968; SHAINBEReGt ul., 1971; LOOMIS el al., 1973). We investigated the relationship between cell fusion and the activity of specific enzymes, in order to verify whether the expression of these phenomena is linked to a common regulative signal. The activity of creatine kinase (CPK; E.C. 2. 7. 3 2.) has been investigated in culture conditions which prevent cell fusion without affecting cell growth. These culture conditions consisted of the use of a nutritional medium at low serum concentration (MOLINAROet al., 1974). The inhibition of cell fusion obtained by low serum concentration depends primarily on the reduced Ca++ concentration, since the addition of Ca++ restores cell fusion