Measurement of proteoglycans, elastase, collagenase and protein in synovial fluid in inflammatory and degenerative arthropathies.

The number of leucocytes and the concentrations of protein, proteoglycans (PG), elastase a1 proteinase inhibitor complexes (E-alpha 1 Pi) and collagenolytic activity were measured in the synovial fluid (SF) of 15 patients with rheumatoid arthritis (RA) and 18 with osteoarthritis (OA). The mean levels of protein, E-alpha 1 Pi and collagenase and the number of leucocytes were higher in RA than in OA SF. However, the mean level of PG was higher of OA SF than in RA. In the latter, they were principally in the form of monomers and fragments while in the former they were in the form of aggregates and monomers. There was a direct relationship between the concentration of E-alpha 1 Pi and either the number of white cells or the concentration of synovial proteins, suggesting that the measurement of E-alpha 1 Pi complexes is a biochemical index of the local inflammatory reaction. There was an inverse correlation between the concentrations of PG and E-alpha 1 Pi which may reflect the effect of degradation in PG of elastase and other enzymes released at the same time. Finally, there was a direct relationship between the concentration of E-alpha 1Pi and collagenase which may be the reflection of a simultaneous release of various enzymes from leucocytes and macrophages.