[Respective roles of high and low molecular weight serum growth factors in the metabolism of proteoglycans and other cartilage macromolecules].

35S radiolabeling allowed an evaluation to be made of neosynthesized macromolecules in chick embryo cartilage cultures. Activities for growth factors of high (serum retentate) or low (ultrafiltrate below 1,000) molecular weight (MW) were assessed in pelvic cartilage explants and in corresponding incubation media. In the absence of growth factor, 35S was mostly incorporated in glycosaminoglycans (GAGs) as regards the medium and for cartilage, in guanidinium chloride unextractable material. In retentate-enriched medium, 35S incorporation was enhanced in all cartilage GAGs while in the medium, stimulation essentially occurred in macromolecules other than GAGs. Low MW growth factors exclusively enhanced cartilage levels of macromolecules which were insoluble in guanidinium chloride. In the medium, these factors did not display any significant effect. These results indicate that human serum growth factors with high and low MW possess different metabolic targets at the cellular level.