Binding of synovial fluid proteins to monosodium urate crystals in vitro

Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS PAGE) and western blot techniques were used to analyze proteins adsorbed in vitro to synthetic monosodium urate crystals (MSUC) from a variety of gouty biologic fluids. Distinct differences in adsorbed proteins were found in comparing synovial fluid (SF) with serum or plasma, particularly at 220 kD and below 19 kD. Further studies should consider the importance of the synovial milieu. Patterns of proteins adsorbed to MSUC from the SF of all 12 patients with gout were similar. A considerable number of polypeptides appeared to be selectively adsorbed. Of these, polypeptides associated with fibronectin, C1q and IgM were identified by immunotransblotting. The experiments also demonstrated that the overall polypeptide patterns obtained by SDS PAGE of eluates from MSUC exposed to SF were unaffected by heating MSUC to 180 degrees C, as well as by the volume of SF in the incubation mixture.