Histochemical demonstration of myosin Ca2+-ATPase accumulation in primary cultures of skeletal and heart muscle cells.

A modified histochemical technique is described for the improved detection of myosin Ca2+-ATPase activity in single muscle cells in culture. The method was used to demonstrate the increase in myosin Ca2+-ATPase activity in differentiating chick skeletal muscle cells. Functional muscle cells were also positively identified in the heterogeneous cell population of primary hamster heart cell cultures. An age-dependent increase in the number of cells with high levels of myosin ATPase activity in mitotically arrested heart cell cultures was shown. Maturation of individual muscle cells could thus be evaluated.