Abstract
The incorporationin vitro of35S-sulphate into chondroitin sulphate fractions, quantitatively assessed and separated, was studied in different layers of bovine articular cartilage in relation to age. After incubationin vitro in Tyrode solution with35S-sulphate the specimens were washed for 12 hours in saturated sodium sulphate solution. No loss of chondroitin sulphate occurred in the young and adolescent articular cartilage after the incubation and washing procedures. Thus, the proteoglycans appear to be firmly bound within this cartilage In contrast, large losses of chondroitin sulphate were found from the epiphyseal cartilage. In the cow, no chondroitin sulphate was lost from the superficial layers but increasing losses of both chondroitinand keratansulphate occurred from the middle to the deep layers. In all ages, the articular surface layer 40 μ in thickness showed high “specific activities” in the different chondroitin sulphate fractions and incorporation of35S-sulphate into chondroitin sulphate of predominantly high molecular weight and/or charge density suggesting an increased turnover rate of these fractions. In the matrix of this layer, the chondroitin sulphate consisted of predominantly low molecular weight/low charged fractions. In the other layers, a pattern of35S incorporation was found largely reflecting the actual chondroitin sulphate distribution pattern. This suggests that sulphation is completeted intracellularly. Further, the data suggested similar turnover rates for the different chondroitin sulphates. Increased incorporation of35S-sulphate into chondroitin sulphate at higher ages indicated increased rate of synthesis, probably secondary to increased degradation.
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