AN EVALUATION OF THE ROLES OF OESTROGEN, PROGESTERONE AND RELAXIN IN PRODUCING RELAXATION OF THE SYMPHYSIS PUBIS OF THE OVARIECTOMIZED MOUSE, USING THE TECHNIQUE OF METACHROMATIC STAINING WITH TOLUIDINE BLUE

Abstract

SUMMARY: 1. In uninjected ovariectomized mice, the matrix of the symphysial cartilage, like that outside the symphysis, is strongly metachromatic. Following nine daily injections of 1·5 μg oestradio, metachromasia disappeared from the caudal part of the symphysis and decreased in the cranial part, accompanied by swelling of the matrix. Cartilage outside the symphysis was not affected. Hyaluronidase banished metachromasia from both symphysial and extrasymphy. sial cartilage but did not cause swelling of the matrix. Disappearance of metachromasia is attributed to depolymerization or breakdown of the molecules of chondroitin sulphate, resulting in a more pliable ground substance. Swelling is tentatively attributed to uptake of water. 2. One injection of relaxin at the end of such pretreatment produced, by lateral displacement of the two halves of the pelvis, a gap in the middle of the cartilage. Subsequent injections increased this displacement which, it is suggested, may be an indirect effect of relaxin acting through tensile forces mediated in some way as yet unknown. 3. When large doses of progesterone were given simultaneously, oestradiol was less effective in abolishing metachromasia. 4. It is suggested that during pregnancy, oestrogens, perhaps through local liberation of an enzyme, break down the polysaccharides of the symphysial cartilage and make the matrix sufficiently pliable to respond to tensions set up by relaxin during the last week of pregnancy. 5. Separation of the innominates, produced by prolonged treatment with oestradiol alone, is a different process brought about by resorption of bone on either side of the symphysis and not involving lateral displacement of the two bones.