Intracellular Synthesis of Protein-polysaccharides by Slices of Bovine Costa1 Cartilage

An understanding of the interrelationships between cells and the intercellular substance of cartilages may help resolve the question of why some cartilages ossify and others do not. Thus far, in autoradiograms of growing bones, S%ulfate has been seen concentrated initially in chondrocytes (l-3), from which it is extruded into the matrix (1)) and thence, a portion of the label persists in the bone that replaces the cartilage (4, 5). Chondroitin sulfate labeled in the ester sulfate group has been isolated from cartilages after the administration of Szisulfate to animals (6,7) or after incubation of slices of cartilage in buffered solutions of salts containing S35-sulfate (8, 9). Furthermore, it has been found (10) that the turnover rates of chondroitin sulfate are similar when (Y-labeled precursors or Ss5-sulfate are used. It has been concluded, therefore, that Sss-sulfate does indeed serve as a convenient and appropriate marker in turnover studies of chondroitin sulfate. However, nearly all, if not all, of the chondroitin sulfate is present in cartilages as part of more complex macromolecules (ll), which have been termed chondromucoproteins (ll), protein-polysaccharides,’ (12)) or protein-polysaccharide complex (13). In view of this, it was of interest to determine whether the polysaccharide moiety and the protein moiety were synthesized simultaneously by chondrocytes. It has been reported (13) that in costal cartilage of rats, the two moieties are catabolized at similar rates.