THE EFFECTS OF PAPAIN, VITAMIN A, AND CORTISONE ON CARTILAGE MATRIX IN VIVO.

The extreme and, apparently, selective vulnerability of chondromucoprotein in cartilage matrix to the action of proteolytic enzymes in vivo provides a useful model for studying factors involved in the transport, inhibition, and activation of a protease, papain, in the blood and tissues. The lysis of cartilage matrix which occurs in hypervitaminosis A is the result of release, probably from chondrocytes, of cathepsins normally contained within lysosomes. Cortisone possesses two properties which are not only of importance for this experimental model but also may have more general bearing on the physiological functions of this hormone with respect to connective tissue. One property is to prevent the resynthesis or deposition of chondroitin sulfate in cartilage matrix, after depletion of the latter. The other, which may be relevant to the "anti-inflammatory" actions of cortisone, is to increase the stability of lysosomes and prevent release of the acid hydrolytic enzymes contained in these organelles.