Age related changes in the turnover of proteoglycans from explants of bovine articular cartilage.

Articular cartilage in explant culture synthesized 2 proteoglycan types of different size. The proportion of 35S-sulfate incorporated into the small proteoglycan was higher in mature (17%) than in immature cartilage (11%). The chondroitin sulfate chains of both proteoglycans, synthesized by mature cartilage were shorter than those of immature cartilage, with a higher ratio of 6-sulfated over 4-sulfated disaccharides. Radiolabelled macromolecules from tissue of both ages were released in 2 phases: an initial fast release followed by a period of slow release. The half-lives of both proteoglycan populations were shorter in mature cartilage than in immature tissue (-45%). The amount of proteoglycans released during the initial short phase increases with age, from 23-24% in immature cartilage to 28-29% in mature tissue.