Hexosamine-containing glycoproteins of normal bovine synovial fluid.

Synovial fluid is usually considered to be a modified extracellular fluid or blood dialysate (1, 2). It is now well known that all of the electrophoretically classified groups of proteins found in serum are also, at least qualitatively, present in synovial fluid (3-8). This does not mean, however, that all proteins can pass the capillary membranes, because cholesterol and fats, usually associated with lipoproteins, are absent from the normal fluid (1, 2). The proportion of albumin is greater in human and bovine synovial fluids than in the respective serum, suggesting that a slight generalized permeability (or perhaps selective permeability) exists for molecules of molecular weights of about 65,000 or less. On this account, glycoproteins of similar or smaller molecular weight might also be present in synovial fluid to a greater degree than in serum. It is the purpose of this report to demonstrate a generalized enrichment of (IIand P-hexosaminecontaining glycoproteins’ in synovial fluid. Bovine fluids and sera were used because of the ease with which these materials are obtained; sufficient fluid is generally obtainable from human subjects only as traumatic effusions. Schmid et al. have shown that such effusions contain many of the proteins common to serum (9, 10). Unfortunately trauma is also accompanied by an increase in permeability (2) ; hence, data obtained with such fluids do not strictly describe the normal composition. One might also object that bovine synovial fluid obtained at a slaughterhouse is not quite normal, as the animals may have stood for long periods of time in transit. Nevertheless, it is felt that carefully selected bovine fluids will present a relatively normal picture of the glycoproteins present.