Papain-induced changes in rabbit cartilage; alterations in the chemical structure of the cartilage matrix.

Some biochemical aspects of the collapse of the rabbit ears produced by the intravenous injection of papain have been studied. A marked depletion of chondromucoprotein (M.C.S.) and a reduction of the S(35) content of cartilage matrix were found to coincide with the gross and histologic changes in the cartilage. At the same time there was a marked increase in the amount of S(35) in the serum and an increase of S(35) and glucuronic acid excreted in the urine. Alteration in the composition of the M.C.S. remaining in the cartilage of the papain-injected animals was detected. The findings indicate that the collapse of the rabbit ears is due to loss of chondromucoprotein from cartilage and reduction of chondroitin sulfate in the chondromucoprotein that remains. All these changes were reversed in recovery.