Release of mast cell mediators and nitrites into knee joint fluid in osteoarthritis--comparison with articular chondrocalcinosis and rheumatoid arthritis.

In order to address the issue of the role of mast cells and nitric oxide (NO) in joint effusions occurring in the course of osteoarthritis (OA), synovial fluids collected from the knee of patients with OA, articular chondrocalcinosis and rheumatoid arthritis (RA) were studied for number of mast cells, and histamine, tryptase, phospholipase A2 and nitrite content. Mast cell counts are elevated in synovial fluid from OA patients when compared with RA. Histamine content in synovial fluid parallels the number of mast cells. Tryptase levels are elevated in OA in comparison with both other conditions, but do not reach the level of significance. Identical phospholipase A2 levels are recorded in three groups. Nitrite concentrations are also higher in synovial fluid from OA patients when compared with RA patients. These results suggest that mast cells in association with various inflammatory cells, may contribute to inflammation and cartilage breakdown in OA.