The role of catabolin in the control of cartilage matrix integrity.

Living articular cartilage may be stimulated to degrade its matrix totally by the influence of catabolic messengers. One such messenger which has been isolated and purified from synovial tissue and blood leukocytes is catabolin. This is a 20,000 molecular weight pI 4.5 protein, which acts on living chondrocytes in subnanogram concentrations. Studies on its synthesis, translocation, and secretion from synovial tissue are reported. Its secretion, but not its principal function, is inhibited by cortisol. Its mode of action appears to be in invoking catabolic responses from effector cells. It may also inhibit the synthesis of matrix components. The possible role of catabolin and other messengers in arthritis will be considered.