REGIONAL DIFFERENCES IN THE RISE IN BLOOD-LEVELS OF ANTIGENIC KERATANSULFATE AND HYALURONAN AFTER CHYMOPAPAIN INDUCED KNEE-JOINT INJURY

Objective. Results from several recent studies suggest that the levels of antigenic keratan sulfate (agKS) and hyaluronan (HA) in serum prov ide useful information about changes taking place in injured or diseas ed synovial joints. To improve our understanding of the significance o f such changes, we investigated the points of entry of these molecules into the blood circulation and their subsequent clearance after exper imentally induced injury to rabbit knee joint. Methods. Chymopapain wa s injected into knee joints of 8 young adult rabbits to induce aggreca n degradation in articular cartilage within the injected joint. Levels of agKS and HA in serum from various blood vessels were measured befo re and 5 h after the injury. The statistical significance of injury re lated changes and differences among the different vessels were evaluat ed. Results. After the injury, the level of agKS rose most significant ly in the popliteal vein draining the injected knee joint and dropped rapidly by the time the blood reached the femoral vein. The level of a gKS was similar, although lower, in other blood Vessels but, in each c ase, it was significantly higher than before the injection. The level of HA showed a different pattern of changes after injection. While hig hest in the popliteal vein draining the injected knee, HA was markedly elevated in the cranial vena cava, close to the entry of lymph into t he circulation, and was 50% lower in the hepatic than in the portal ve in. Conclusion. (1) Measurement of agKS and HA in a blood vessel drain ing or close to an injured/diseased knee joint may provide more specif ic information about degradative changes taking place in that joint th an measurement of levels of these markers in other blood vessels; (2) some HA molecules but no measurable amounts of agKS enter the blood ci rculation via the lymphatic system; and (3) HA but not agKS is very ra pidly cleared from the blood by the Liver.