Protease Activity in Synovial Tissue Extracts

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Abstract
Extracts from synovial membranes obtained from 10 patients with rheumatoid arthritis and 8 patients with non-rheumatoid arthritis were examined for protease activity at different pH on casein, haemoglobin and albumin. At least two different activities are demonstrable. One, which is most pronounced in rheumatoid tissue, has characteristics corresponding to cathepsin D activity. One, presumably due to the fibrinolytic system, is less active in rheumatoid than in non-rheumatoid tissue extracts. Breakdown products of fibrinogen after degradation by the synovial tissue extracts and plasmin are characterized immunoelectrophoretically. The patterns obtained after digestion with non-rheumatoid extracts correspond to those seen after profound plasmin degradation, and the patterns after digestion with rheumatoid tissue extracts to less profound degradation. The latter are very similar to the immunoelectrophoretic patterns of breakdown products found in inflammatory, especially rheumatoid, synovial fluid, but are not more resistant to further plasmin digestion than normal fibrinogen-fibrin. The resistance of breakdown product in rheumatoid synovial fluids is presumably due to complex formations between breakdown products and other proteins, polysaccharides and others.

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