A COMPARATIVE-STUDY OF THE COMPOSITION OF DISKS AND OF PROTEOGLYCANS FROM DIFFERENT SPINAL LEVELS OF SHEEP

Compositional analyses were undertaken on lumbar (L2L3 - L5L6) and lum bosacral (L6S1) intervertebral disc tissues from young adult (2-year-o ld) merino wethers. The proteoglycan level in the nucleus pulposus of the lumbosacral disc was significantly lower than that found in the nu cleus pulposus of lumbar levels (p < 0.05). The annulus fibrosus was r icher in collagen compared to the nucleus pulposus in all discs examin ed, and the lumbosacral disc consistently had both higher annulus fibr osus and nucleus pulposus collagen levels than lumbar discs (p < 0.05) . Aggregation of the high buoyant density proteoglycans, with hyaluron ic acid, was generally higher in annulus fibrosus proteoglycans than n ucleus pulposus proteoglycans irrespective of the spinal level examine d. Examination of the intervertebral disc proteoglycans, by composite agarose polyacrylamide gel electrophoresis, demonstrated three proteog lycan subpopulations and that the nucleus pulposus generally contained a greater proportion of higher mobility more polydisperse proteoglyca n species than the annulus fibrosus.