INSULIN-LIKE GROWTH-FACTOR-I AND ITS BINDING-PROTEIN-3 AND BINDING-PROTEIN-4 ARE INCREASED IN HUMAN INFLAMMATORY SYNOVIAL-FLUID

Objective. To measure insulin-like growth factor I (IGF-I) and its bin ding proteins (IGFBP) in human synovial fluid (SF), as IGF-I resistanc e in the chondrocyte was implicated in the pathogenesis of inflammator y arthritis. Methods. Ten patients with inflammatory arthritis and 7 c ontrols were evaluated. IGF-I and IGFBP 3 were measured by radioimmuno assay while all IGFBP were evaluated by Western ligand blotting. Resul ts. Serum IGF-I did not differ between patients and controls (22.3 +/- 2.9 vs 22.0 +/- 3.0 nmol/l), while significantly higher values were f ound in inflammatory SF compared with noninflammatory SF (14.7 +/- 1.5 vs 10.2 +/- 1.2 nmol/l; p = 9.05). IGFBP-3 and IGFBP-4 were the most prominent bands found in inflammatory SF by Western ligand blotting. T he 24 kDa IGFBP-4 band appeared faintly in 2 noninflammatory effusions and was nearly absent in others. IGFBP-3 levels in sera from the 2 gr oups did not differ (2.9 +/- 0.3 vs 2.5 +/- 0.3 mg/l), but were signif icantly higher in inflammatory compared with noninflammatory effusions (1.5 +/- 0.2 vs 0.9 +/- 0.2 mg/l; p = 0.05). Conclusion. The pattern of IGFBP in SF differs in inflammatory versus noninflammatory joints.