THE EFFECT OF OESTRONE AND PROGESTERONE ON THE HISTOLOGICAL STRUCTURE OF THE SYMPHYSIS PUBIS OF THE CASTRATED FEMALE MOUSE

Abstract

1. The effect on the symphysis pubis of oöphorectomized mice of oestrone (1·5 μg./day) and progesterone (1·0 mg./day) injected separately and simultaneously for 8–20 days has been investigated histologically. 2. A brief course of treatment with oestrone had a definite effect on the pelvis, greater than appears on X-ray photographs, but not comparable in intensity with that which follows the addition of relaxin. 3. The action of oestrone affected the dorsal bony walls of the two innominates, and started at the anterior symphysial borders. Simultaneous resorption of the outer or periosteal surfaces, and deposition of new bone on the endosteal surfaces occurred, until the marrow cavities were obliterated at least in the medial parts of the two innominates. Resorption then continued so that the solid symphysial borders of the bones gradually disappeared. No ligament proliferation occurred. 4. A vascular, richly nucleated tissue replaced the resorbed dorsal surfaces of the bones, and was thought to be derived mainly from the marrow. Many osteoclasts were present along the eroding surfaces but the origin and function of these enigmatic cells is still undecided. 5. When progesterone was given for periods up to 20 days the histological structure of the symphysis pubis was similar to that of untreated control animals. 6. When oestrone and progesterone were given simultaneously for periods up to 20 days changes were produced of the same type as, but much less pronounced than, those produced by oestrone alone. 7. The results of histological investigation support the conclusion that progesterone is not only ineffective in producing relaxation of the pelvis in the mouse but that, at least in certain dose ratios, it inhibits the action of oestrone on the symphysis.