Cytochemical localization of calcium in myoblasts of the chick embryo myotome

Abstract

Muscle fibers are derived from multinucleated myotubes which are themselves formed during embryonic development by the fusion of mononucleated myoblasts. Myoblast fusion results from a sequence of different and highly orchestrated stages demonstrated previously in vitro: recognitionalignment, adhesion and membrane fusion. Like many other fusion systems, myoblast fusion is Ca2+- dependent. The role of Ca2+is multiple since it is needed for muscle cell differentiation, for the alignment stage and it has also been demonstrated that Ca2+influx precedes fusion increasing free intracellular Ca2+. It has been proposed that this increase in free intracellular Ca2+may activate an enzimatic cascade which leads to membrane fusion.The present study, using the K-pyroantimonate method, describes Ca2+localization and storage in myoblasts before fusion for the first time, since this method had not been applied to skeletal muscle development studies before. Chick embryos from 51 to 108 h. of incubation (Hamburger and Hamilton stages 16 to 25) were used.