[Detection of low molecular weight trypsin inhibitors in small samples of cartilage, cartilage extracts and synovial fluid by gel diffusion].

The radial diffusion assay is a very useful method for detection of low amounts of proteinase inhibitors in biological materials. The determination of low molecular weight (LMW) inhibitors in the presence of high molecular weight inhibitors is possible by the combination of radial diffusion and ultrafiltration. Using this method LMW trypsin inhibitors could be demonstrated in human articular cartilage, but not in human synovial fluid. In cow, pig and sheep a LMW trypsin inhibitor could be found in both the articular cartilage and in the synovial fluid. On the other hand, a LMW trypsin inhibitor could not be found neither in the canine cartilage nor in the canine synovial fluid. The method allows also the direct determination of LMW trypsin inhibitors in cartilage extracts in the presence of 4 M guanidinium hydrochloride or 6 M urea. Therefore, the method is recommended for direct determination of LMW inhibitors by column chromatographic separations of inhibitors.