The aminoterminal-type-III procollagen peptide and proteoglycans in serum and synovial fluid of patients with rheumatoid arthritis or reactive arthritis.

The concentrations of aminoterminal-type-III procollagen (procollagen N-) peptide, and of proteoglycans were measured in knee-joint synovial fluid and serum from patients with rheumatoid arthritis or reactive arthritis. All synovial fluids contained large amounts of intact propeptide. The synovial fluid: serum propeptide ratios were high, suggesting local propeptide liberation. A correlation was demonstrated between the propeptide concentration in synovial fluid and in serum. In rheumatoid arthritis, the propeptide concentration in synovial fluid was related to local inflammatory activity, and the serum concentration was correlated with the presence of nonspecific markers of inflammation. The presence of smaller propeptide fragments in synovial fluid indicated that some degradation occurred locally. The local metabolic changes were most prominent in patients with joint erosions. Patients with nonerosive rheumatoid arthritis and reactive arthritis had similar synovial fluid propeptide concentrations. The proteoglycan content of synovial fluid was inversely related to the degree of joint destruction, and was highest in patients with reactive arthritis. No correlation was observed between the concentrations of propeptide and proteoglycan in synovial fluid. Intraarticular glucocorticoid injection reduced the levels of propeptide and proteoglycan in synovial fluid.