Development and regulation of the phosphorylase-glycogen complex in myogenic cells of the L6 line.

The development of the phosphorylase-glycogen complex was studied in cells of the myogenic line L6 at different stages of differentiation. Our results indicate that the complex is already present in mononucleated myoblasts. However, several features of the complex observed in the myoblasts, such as the total amount of phosphorylase bound to the polysaccharide, and the type of glycogen agglomerates present in the cells, differ from those of the myotubes. It is postulated that at the moment when the myoblasts differentiate, definitive metabolic events take place. At this time the protein-glycogen complex is completed, phosphorylase being bound to small glycogen particles, and the multinucleated myotubes begin to accumulate a reserve of free glycogen. This latter constituent is mobilized first upon glucose starvation.