Protein traffic in human synovial effusions.

Concentrations of 5 marker proteins were measured in synovial fluid and serum samples from knee effusions of 11 patients with rheumatoid arthritis and 9 with osteoarthritis. Indirect determinations of synovial plasma flow and lymphatic drainage were obtained by measuring iodide clearance (ml/minute) and radio-albumin clearance (ml/minute). Together with protein concentrations, these determinations allowed us to calculate: the flux of each marker protein through synovial tissues (mg/minute); the volume of plasma cleared by synovium per unit time (ml/minute); and the fractional extraction per passage through the synovial microcirculation (protein permeance). These measures differed substantially between rheumatoid arthritis and osteoarthritis patient populations and quantified the severity of the microvascular lesion in rheumatoid synovitis.