A quantitative study of metachromasy in synovial fluid and mucin

Spectrophotometric measurements on synovial fluid and solutions of mucin and hyaluronate in the presence of methylene blue showed that: 1. Dialyzed synovial fluid was not metachromatic. 2. Albumin and gelatin at a concentration of 1 mg. per ml. inhibited the metachromasy of strong chromotropes. 3. Reduction of the protein of synovial fluid by the use of proteolytic enzymes still did not make the synovial fluid chromotropic. 4. Mucin solutions, with a protein content equal to that of protease-treated synovial fluid, were intensely metachromatic. 5. Sulfur-free hyaluronate produced intense metachromasy. The evidence presented indicates that in its native state in synovial fluid hyaluronate is either bound or its anionic groups are not entirely free.