Unusual Properties of Hyaluronateprotein Isolated From Pathological Synovial Fluids*

In joints actively involved by rheumatoid ar- thritis, the nature of the synovial fluid is quite different from normal.The fluid is increased in volume (10 to 30 ml) and contains large numbers of leukocytes (> 10,000 per mm3) .The concen- tration of protein (4 to 5 g per 100 ml) is more than twice that of normal synovial fluid, whereas the concentration of hyaluronate (0.1 g per 100 ml) is reduced to one-third to one-half normal.Many studies have been made of the physical properties of rheumatoid synovial fluid (1), and although these reflect the physical state of the hy- aluronate in the fluid, the hyaluronate has not been isolated for study.Recently, mild methods were described to isolate hyaluronate from normal synovial fluids (2).Hyaluronate containing about 2% protein was obtained, and this product was called hyaluronateprotein (HP).Similar methods were used to isolate hyaluronate from rheumatoid synovial fluids, and a number of unusual findings were observed.A compound of hyaluronate combined with more protein (about 10%o) was isolated from the ma- jority of the fluids; some of these products formed gels during dialysis in acetate buffer at pH 4.5, and all showed immobilization at the origin during zone electrophoresis at pH 4.5.None of these properties of the hyaluronate in rheumatoid syno- vial fluids has been previously described.During the course of these studies, the question arose whether such findings were specific for HP from rheumatoid fluids.It appears that they are not, for in