Effect of papain on the skeletal and general development of the rat.

Abstract

59 young male and female rats were injected with crude papain for 28 days and this hindered the growth of the skeleton. Two kinds of controls were used as comparisons: (1) littermates were pair-fed with those receiving papain, which kept them in a state of moderate undernutrition, and this was revealed in their physical characteristics; (2) other littermates were fed <i>ad libitum </i>throughout the whole experiment. Some rats in each of these three groups were killed at the end of the period of injection, the remainder were given unlimited food and no other treatment till they were 6 or 12 months old. The bodies and tails of the papain-treated rats were short compared with those of pair-fed animals of the same body weight; the long bones were also short, but of similar width. The composition of the bone appeared to be normal. The muscles attached to the long bones were necessarily short, but they, like the bones, were wide for their length. The weights of the heart, lungs and brain were similar in the papain-treated and pair-fed animals of the same body weight, but the kidneys, spleens and pituitaries were consistently larger in the papain-treated ones. The livers were also larger, but the undernutrition of the pair-fed animals was responsible for the small size of their livers. Papain hindered the growth of the stomach and small intestine but promoted the growth of the large intestine Most of these differential effects on the organs were still evident when the animals were killed at 6 months of age. The testes, moreover, had now become heavier in the animals previously treated with papain than in either of the two control groups, although the rats themselves were much smaller. Papain is known to act on the mucopolysaccharide-protein complexes in the epiphyseal plates and this is what hinders the growth of the bones. It is suggested that papain also acts on similar mucopolysaccharide-protein complexes in the elastic capsules surrounding the kidneys, spleen and testes so that there is no longer the usual restricting influence on the blood supply and growth of these organs.