Proteoglycans from rabbit articular and growth plate cartilage. Ultracentrifugation, gel chromatography, and electron...

Proteoglycans are considered to be important for the mechanical properties of articular cartilage and growth plate and for the regulation of calcification of growth plate. We have used ultracentrifugation, gel chromatography, and electron microscopy to characterize and compare proteoglycans isolated from rabbit articular cartilage, uncalcified growth plate, and calcified cartilage. We found that proteoglycans from articular cartilage were more resistant to extraction than were proteoglycans from uncalcified growth plate and calcified cartilage. Long term neutral decalcification of calcified cartilage resulted in degraded proteoglycans. The chondroitin sulfate chains from all three tissues had similar size distribution. Gel chromatography and electron microscopy of proteoglycan monomers suggested that those from uncalcified growth plate were largest, those from articular cartilage intermediate, and those from calcified cartilage smallest. Proteoglycan aggregates from articular cartilage were longer than those from uncalcified growth plate. Both biochemical and quantitative electron microscopic data suggested the existence in mineralizing cartilage of at least two different sized populations of proteoglycan aggregates.