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NMR relaxation rates were related to the composition of the nucleus pulposus from 11 and anulus fibrosus from six human intervertebral disks. Tissue water was proportional to glycosaminoglycan (GAG) and residue, the noncollagen, non-GAG portion of the dry weight (R2 = 0.74). The solid signal fraction depended on collagen and residue protons (R2 = 0.89). 1/T1 was proportional to collagen and residue (R2 = 0.97). T2 showed 2-4 components labeled A, B, C, and D, with means +/- standard deviations of 3.1 +/- 1.6, 17.5 +/- 9.5, 64 +/- 22, and 347 +/- 162 msec. Signal fractions of A and B depended on the collagen-associated water protons (R2 = 0.94 and 0.85), C on residue-associated water protons (R2 = 0.82), and D on GAG-associated water protons (R2 = 0.74). The data led to a model of disk architecture in which the collagen and residue were largely solid, forming distinct water compartments; the remaining water was present in a proteoglycan gel.

The methods of Hascall & Sajdera (1969) 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 centrifugated in 0.4M-guanidinium chloride in a CsCl gradient. Analytical ultracentrifugation of the hexuronate-containing heavy component revealed two fractions. both more polydisperse than those of cartilage. Also the more rapidly sediminting 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.

This paper reports on our investigations of the glycosaminoglycans (GAGs) (hyaluronic acid, chondroitin-6-sulfate, and keratan sulfate) of 13 adjacent zones of normal and scoliotic discs obtained at necropsy. The isolation and separation of these GAGs on the microgram scale was achieved using the different solubilities of the calcium and cetyl pyridinium chloride complexes. In normal discs the distribution of these GAGs is symmetric about the nucleus pulposus where their concentration is highest, and lowest in the outer annulus regions. A shift in this distribution profile was observed for the GAGs of the scoliotic discs, particularly at the apex of the curve. On the concave side of this disc the chondroitin-6-sulfate was elevated relative to discs at a lower level. In those annulus zones on the convex side of the curve, the keratan sulfate and hyaluronic acid levels were elevated and chondroitin sulfate depressed. These results suggest the presence in these respective regions of at least two different species of proteoglycans accompanied by elevated hyaluronate levels.