Effect of Temperature on the Metabolism of Proteoglycans in Explants of Bovine Articular Cartilage

The turnover of proteoglycans in bovine articular cartilage was determined in explant cultures, maintained at 32°C or 37°C. Both the rate of proteoglycan synthesis and the release of newly synthesized proteoglycans were decreased in cultures incubated at 32°C compared to 37°C.

At both temperatures the newly synthesized proteoglycans were similar in hydrodynamic size and chain length of the glycosaminoglycans. However, the ratio of 6-sulfated disaccharides over 4-sulfated disaccharides of the newly synthesized glycosaminoglycans, differed less from the endogenous ratio at 32°C than at 37°C.

At both temperatures, the incorporated ³⁵S-sulfate is released from explants in two pools. Twenty-three percent of the ³⁵S-radiolabel was released into the culture medium during an initial short phase (t_1/2 = 1.1 day at 32°C, 1.3 day at 37°C), 77% had a much longer half-life. The lowered temperature markedly decreased the release of ³⁵S-sulfate with a slow turnover (t_1/2 = 60 days at 32°C, 38 days at 37°C).