Proteoglycan aggregates in adult human costal cartilage

Abstract

1. 1. A sequential extraction procedure using isotonic KCl and 4.0 M guanidine hydrochloride was used to solubilise proteoglycans from adult human costal cartilage under conditions minimising autolysis. Up to 28% of the total tissue hexuronate was extracted. 2. 2. Proteoglycan fractions were prepared from the extracts by CsCl equilibrium density gradient centrifugation. 3. 3. Each fraction exhibited distinct electrophoretic heterogeneity. 4. 4. Proteoglycans extracted by isotonic solutions are relatively small and may be in vivo degradation products of whole molecules. The major fraction (A 1) from high ionic strength extracts has a composition similar to that of A 1 proteoglycans from adult human articular cartilage. A 2 fractions differ and are highly enriched in protein. 5. 5. A 1 and A 2 fractions high ionic strength extracts contain proteoglycan can aggregates, but to a much lesser extent than found on other cartilages like bovine nasal or porcine epiglottal cartilage. 6. 6. The aggregates can be dissociated and a ‘subunit’ proteoglycan isolated by CsCl density gradient centrifugation in 4.0 M guanidine hydrochloride. ‘Subunits’ can reaggregate partially, when mixed with fractions of lower density from the gradient.