The methods of were used to compare the proteoglycans of human intervertebral disc with those of bovine nasal cartilage. In contrast with cartilage, most of the hexuronate of disc could be extracted at low shear with water or dilute salt solutions. Extracts of disc with 4M-guanidinium chloride were centrifuged in 0.4M-guanidinium chloride in a CsCl gradient. Analytical ultracentrifugation of the hexuronatecontaining heavy component revealed two fractions, both more polydisperse than those of cartilage. Also the more rapidly sedimenting component was a much smaller fraction of the total. After prior extraction with 0.4M-guanidinium chloride, 4M-guanidinium chloride extracts of disc were found, by ultracentrifugal analysis, to be enriched in components resembling the proteoglycan monomer and aggregating factors of cartilage.

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