Troponin in Cultured Chicken Breast Muscle Cells: (troponin / muscle cell / chicken)

The onset of troponin accumulation and the localization of troponin in cultured chick embryo skeletal muscle cells were studied by means of indrect immunofluorescent microscopy. At 31 hr after plating, troponin components were detected in 54-62% of total mononucleated myogenic cells and in all myotubes as longitudial fibrous structures. 3 H-thymidine incorporation stduy coupled with the immunofluorescent microscopy showed that mononucleated myogenic cells at the mitotic stage did not contain troponin. As myotube maturation proceeds, the troponin-containing fibers were organized into cross-striated structures. At the myotube stage, muscle cells were labeled with 35 S-methionine and proteins synthesized were analyzed by two-dimensional gel electrophoresis. It was found that myotubes in culture synthesized both fast and slow types of troponin-I and-C. Our results suggest that fast and slow types of troponin components are synthesized in cultured skeletal muscle cells before or at the early phase of myofibrillogenesis.