Papain-induced mitosis of chondrocytes in adult joint cartilage: an experimental study in full-grown rabbits.

When diluted papain is injected intra-articularly into the knee joints of adult rabbits, slowing progressing, degenerative changes develop in the articular cartilage. After intravenous injection of crude papain no significant degenerative changes are found. With the aid of radioactive thymidine, it is possible to demonstrate that the chondrocytes recover their ability to divide before any degenerative changes can be found. At the same time the matrix loses its staining properties with Safranin-O and toluidine blue.