Age-Related Changes in the Incorporation of [35S]Sulfate into Two Proteoglycan Populations from Human Cartilage

Abstract

From human hyaline cartilage (processus xiphoid) preincubated in the presence of [35S]sulfate, proteoglycans were extracted by 4 M guanidinium chloride and divided into 6 age groups. Fractionation of proteoglycans by gel filtration under dissociative conditions resulted in 2 proteoglycan fractions (a and b) with different hydrodynamic volumes. The higher MW fraction a contained chondroitin sulfate, the fraction b keratan sulfate as predominant glycosaminoglycan, the chondroitin sulfate/keratan sulfate ratio decreasing with increasing age in either fraction. The relative portion of proteoglycan fraction b and its 35S-labeling increased with increasing age. From the specific 35S radioactivities of the chondroitin sulfate and keratan sulfate preparations, the occurrence of 2 independent proteoglycan populations is suggested. A precursor-product relationship between proteoglycan fractions a and b was excluded.