Satellite cells of rat muscles as studied by freeze-fracturing.

Satellite cells in rat muscles were studied by freeze-fracturing. They were found not to be fusiform but to have several narrow projections embedded in grooves of the muscle fibre membrane. Short projections of the muscle fibre covering the outer face of the satellite cells were observed as well. In the P-face of the cell membrane of satellite cells, membrane particles and caveolae were less frequently seen than in the P-face of the muscle membrane. Thus the surface of the satellite cells looked more smooth than that of the muscle fibres. Junctions between muscle fibre and satellite cell were not found. The presence of cytoplasmic extensions of satellite cells may suggest that these cells are motile.