Reversible Collapse of Rabbit Ears after Intravenous Papain, and Prevention of Recovery by Cortisone

A substance has been demonstrated in solutions of crude papain, which, when injected intravenously into 1 kilo rabbits, in amounts less than 5 mg., results in complete collapse of both ears. The phenomenon becomes visible 4 hours after injection, and is complete within 24 hours. 3 or 4 days after papain, the ears gradually reassume their normal form. Ear collapse is associated with depletion of the ear cartilage matrix, and the disappearance of basophilia from the matrix. Similar changes occur in all other cartilage tissues, including bones, joints, larynx, trachea, and bronchi. At the time when the ears are restored to normal shape, the basophilic matrix reappears in cartilage. Repeated injections of papain, over a period of 2 or 3 weeks, bring about immunity to the phenomenon of ear collapse. When the arterial circulation to one ear is occluded for 15 minutes at the time of injection of papain, this ear is protected against collapse. The effect of crude papain could not be reproduced by crystalline papain protease or crystalline papain lysozyme, which together comprise a considerable portion of the dry weight of papain. The nature of the responsible factor has not been determined, and the possibility that chymopapain may be implicated is currently under study. Cortisone prevents the return of papain-collapsed ears to their normal shape and rigidity. Possibly this reflects a capacity of cortisone to impede the synthesis or deposition of sulfated mucopolysaccharides in tissues.