METABOLIC TURNOVER OF SULFATED GLYCOSAMINOGLYCANS AND PROTEOGLYCANS IN RABBIT TEMPOROMANDIBULAR-JOINT CARTILAGES WITH EXPERIMENTALLY-INDUCED OSTEOARTHROSIS

Osteoarthrosis-like changes were induced by means of experimental disk perforation in the right temporomandibular joint of rabbits. The turnover of proteoglycans and glycosaminoglycans was studied 16 weeks later, using (SO4)-S-35. Tissues were sampled 1 day and 7 days after injection of the sulfate. The corresponding tissues from the left untreated joint were used as controls. After isolation of the glycosaminoglycans the incorporation of (SO4)-S-35 was estimated by scintillating counting. The extracted proteoglycans were analyzed, using gel electrophoresis, and the distribution of radioactivity was determined by autoradiography, followed by densitometry. Both the synthesis and rate of degradation of the proteoglycans were increased in the experimental disk, compared with those of the control. The net result of these metabolic changes seemed to be losses of small proteoglycans, whereas a slow increase in the number of larger ones may have occurred. The turnover rates of 4- and 6-sulfate increased, although their ratio remained unchanged at this stage of the osteoarthrosis-like process. In the condylar cartilage the turnover of large and small proteoglycans was also increased. The increase was most marked among those containing 6-sulfated galactosaminoglycans. The results concerning the experimental condylar cartilage indicated a decrease in the largest proteoglycan population, whereas the proportion of small proteoglycans was increased.