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The authors measured the activities of four enzymes (L.D.H., acid phosphatase, B glucuronidase, and lysozyme) and the contents of AMPc and GMPc in the synovial fluid in 35 patients with rheumatic disease. In those with various forms of inflammatory rheumatism, they found negative correlation between AMPc and the enzymes, whereas in rheumatoid arthritis they observed a positive correlation between GMPc and these enzymes.

After reviewing previous work on the subjects, the authors show that the synovial fluid in subjects with inflammatory rheumatism contained higher levels of lysozyme and of beta-glucuronidase comparable with those of the acid phosphatases and of lacto-dehydrogenase that they were interested in previously.

The authors show that although the enzyme variations are nil or unimportant in the mechanical joint fluids, they are of some importance in the inflammation fluids, particularly in cases of rheumatoid arthritis. Of those studied so far, the variations are most notable in the dehydrogenases and the phosphatases, the variations being highly significant and related to one another and to the sedimentation rate.

It appears that in rheumatoid arthritis and, to a lesser extent, in the other forms of inflammatory rheumatism, the level of zinc in the blood serum is lowered, whereas synovial zinc is increased. In the synovial fluid, there is a very significant correlation between enzyme activity and the concentration of zinc. Practical experiments aimed at demonstrating in vitro the action of zinc on lacticodeshydrogenase, acid phosphatase, lysozyme and beta-glucuronidase did not produce the anticipated results and do not explain the metabolic disorders of zinc seen during inflammatory rheumatisms.

The authors report that osmic acid, in vitro, increases the activity of beta-glucuronidase in serum and synovial, ascitic and pleural fluids, whereas five other metals of similar molecular weight (platinum, gold, mercury, thallium and lead) are either inactive or inhibitory. By contrast the osmium diminishes the activity of LDH and acid phosphatases in serum and synovial fluid. This effect on beta-glucuronidase is thought to be due to inhibition of a natural inhibitor present in biological fluids, a protein found by several authors.