The metabolic heterogeneity of rabbit ear cartilage chondroitin sulphate

The only glycosaminoglycans that can be isolated from the ear cartilage of 2-month-old rabbits are chondroitin 4-sulphate and chondroitin 6-sulphate. These chondroitin sulphates exhibit molecular-weight polydispersity when isolated from tissue by papain digestion. The chondroitin sulphate is metabolically heterogeneous in that radioactive precursors [(14)C]glucose or [(35)S]sulphate are preferentially incorporated into the higher-molecular-weight polymers both in vivo and in vitro. No transfer of radioactivity from the high-molecular-weight chondroitin sulphate to the low-molecular-weight chondroitin sulphate was seen during 15 days in vivo. It is suggested that there are at least two pools of proteoglycan in the tissue. One of these pools is metabolically active whereas the other is not.