THE REMOVAL OF CARTILAGE MATRIX, IN VIVO, BY PAPAIN

Abstract

The intravenous injection of crystalline papain protease into young rabbits results in rapid, reversible removal of chondroitin sulfate from cartilage matrix throughout the body, provided the papain is inactivated by oxidation or sulfhydryl blocking agents prior to injection. Injection of cysteine-activated crystalline papain produces no change in cartilage. When injected in an inactive state, papain diffuses into cartilage where it becomes reactivated (reduced). Crystalline papain injected in an active (reduced) state fails to enter cartilage, probably because of a reaction with a substrate in the blood. The changes in cartilage produced by injection of inactivated crystalline papain are indistinguishable from those produced by injection of crude papain.