The synthesis and localization of glycosaminoglycans in striated muscle differentiating in cell culture.

Abstract

AbstractDay 3 mass muscle cultures incorporated 35SO4= and 3H· glucosamine into specific glycosaminoglycans that were identified by a variety of methods (enzyme susceptibility, nitrous acid degradation, electrophoresis, thin layer chromatography). More than 75% of the newly synthesized glycosaminoglycans appeared in the medium. In the medium, the glycosaminoglycans consisted of primarily hyaluronic acid (∼35%) and chondroitin sulfate (∼40%) with smaller amounts of chondroitin (∼15%) and heparan sulfate (∼10%). Among the glycosaminoglycans that remained in the cell layer, chondroitin sulfate (∼45%) and heparan sulfate (20‐40%) predominated and only a small amount of chondroitin (∼15%) and hyaluronic acid (∼5%) were present. In both the medium and cell layer, greater than 80% of the chondroitin sulfate was chondroitin‐6‐sulfate. Although mass cultures contain some non‐muscle cell types which undoubtedly contributed to total glycosaminoglycan synthesis, susceptibility of the autoradiographic grains associated with cells in muscle clones to testicular hyaluronidase digestion suggests that at least some glycosaminoglycans (chondroitin sulfate, in particular) were synthesized by muscle cells.Transmission electron microscopy revealed the presence of ruthenium red staining globular units along the surfaces of myotubes. Destruction of the integrity of surface associated ruthenium red stained material by both Streptomyces hyaluronidase and testicular hyaluronidase suggests that both hyaluronic acid and chondroitin sulfate are present on muscle cell surfaces.