HYALURONIC-ACID SYNTHESIS AND TURNOVER BY MYOTUBES IN CULTURE

Analysis of glycosaminoglycan (GAG) synthesis by high density and clonal cultures of chick myoblasts and fibroblasts, and by cultures enriched for myotubes, indicates that all culture types produce hyaluronic acid (HA) and sulfated polysaccharides (S-GAG). Of these cell types the myotube synthesizes the most HA-rich complement of polysaccharides and has the most HA-rich cell surface. It appears that this is the result of decreased S-GAG synthesis rather than increased HA synthesis. Myotube cell surface HA is qualitatively different from HA released to the medium; cell surface HA is predominantly a single high molecular weight species, whereas HA isolated from the medium comprises a heterogeneous mixture of lower molecular weight HA. Since HA molecules of similar size classes can be generated by treating high molecular weight HA with hyaluronidase, an endogenous hyaluronidase could be involved. Alternatively, myotube-enriched cultures may synthesize and secrete HA polymers of several intermediate lengths. © 1979 Academic Press, Inc. All rights reserved.