6-sulphanilamidoindazole arthritis of rats: relation between acute-phase proteins, degree of arthritis and treatment with soybean trypsin inhibitor.

During 6-sulphanilamidoindazole (6-SAI) arthritis a significant increase of serum levels of the protease inhibitor alpha 2 macroglobulin (= alpha 2 acute phase globulin) and of Darcy's glycoprotein was found, whereas the content of female specific protein and of sulfhydryl groups was proved to be significantly decreased. Intravenous administration of 5 mg/kg soybean trypsin inhibitor, twice daily for 4 days, was without any inhibitory effect on paw swelling in 6-SAI arthritis but it caused increased serum levels of alpha 2 macroglobulin and Darcy's glycoprotein. Thus, spontaneous remission of 6-SAI arthritis occurring, despite continued administration of 6-SAI, seems hardly likely to be caused by acute-phase reactants, e.g. via protease inhibition. Evidence is presented which shows that spontaneous remission of 6-SAI arthritis could be due to local processes.