Proteins retained with hyaluronic acid during ultrafiltration of synovial fluid.

The identity of the proteins associated with hyaluronic acid after ultrafiltration of bovine synovial fluid was examined. With discontinuous filtration, alpha2 macro- and IgM globulins were retained in hyaluronic complex both from synovial fluid and from a similar mixture of hyaluronic acid and serum. With continuous filtration and stirring to prevent formation of gels, protein was retained with hyaluronic acid in similar proportions. This protein showed immunologic identity with serum albumin, but differed in amino acid composition. After comparison with results of gel filtration, it was concluded that the identity of the retained proteins can be determined by the concentration of hyaluronic acid without variation in other ionic conditions.