Hydroxyproline levels and collagenolytic activity in synovial fluids of patients with rheumatic diseases

Free, total, and peptide hydroxyproline levels were determined in synovial fluid obtained from the knee joints of 60 patients with theumatoid arthritis (RA), and 26 patients with degenerative joint disease. In addition, in 160 synovial fluid samples obtained from 121 patients including 50 with degenerative joint disease, 60 with RA, 3 with Reiter's syndrome, 3 with hydarthrosis intermittens and 5 with ankylosing spondylitis, the collagenolytic activity was determined. The mean values of free and peptide hydroxyproline in the inflammatory and degenerative fluids were the same, but slight differences were found in the mean values of total hydroxyproline. No effect on the level of free and bound hydroxyproline was observed after treatment with intra-articular hydrocortisone and gold salts. The collagenolytic activity of synovial fluid was registered in 38% of cases of RA and in some cases of Reiter's syndrome and hydrarthrosis intermittens, but it was not found in 50 cases of degenerative joint disease or in cases of ankylosing spondylitis. During a longer observation of patients with inflammatory forms of RA a variability in the collagenolytic activity was observed in repeated examinations of the fluid obtained from the same patient; this activity appeared and disappeared. The incidence of collagenolytic activity and its values were higher in patients with active rheumatoid process and this activity was present more frequently in patients with a short history of the disease (up to 3 years). The collagenolytic activity of rheumatoid fluids was, to a high degree, inhibited by normal human serum. The problem of presence or lack of collagenolytic activity in rheumatoid fluids is discussed.