PROTEOGLYCANS IN THE INTERVERTEBRAL DISC OF YOUNG-DOGS FOLLOWING STRENUOUS RUNNING EXERCISE

The proteoglycans (PGs) of intervertebral disc were studied in ten bea gles which ran on a treadmill for one year (up to 40 km/day) and in te n non-running control dogs. Nucleus pulposus and annulus fibrosus from cervical (C5) and thoracic (T6 and T12) discs were labeled in vitro w ith (SO4)-S-35. The extractability, concentration and synthesis of PGs , and the electrophoretic subpopulations, aggregation and glycosaminog lycan chain lengths of newly-synthesized and total PGs were measured. Sulfate incorporation was significantly elevated by running in the C5 disc and reduced in the annulus of T6 discs. In the annulus of the T6 discs the concentration of total PGs was significantly lower although that of dermatan sulfate PGs was actually higher than in the controls. The results show that enhanced loading of the spine exerts significan t alterations in the intervertebral disc PGs in a spine-level specific manner. In the most strained area of the spine (upper thoracic), the alterations in the runners suggest compromised biomechanical propertie s of the disc.