The action of oestradiol and histamine on the site of nidation in the rabbit. A histological and histochemical study.

Abstract

ABSTRACT Administration of oestradiol causes interruption of pregnancy in the rabbit, but not in man. The morphological changes after injection of oestradiol-benzoate have been investigated in 84 rabbits. Exogenous doses of oestradiol cause necroses and haemorrhages in the endometrium and even in the myometrium of the rabbit. Preceding activity of gestagen, however, is indispensable. Whereas in pseudopregnancy, doses greater than 10 μg/kg bring about a visible effect, 2 μg/kg is sufficient during pregnancy. Necroses are found in the decidua basalis, followed by a disturbance of blood circulation in the placenta. 1 μg/kg oestradiol-benzoate only destroys the decidua marginalis and the marginal parts of the placenta. Similar changes are physiological. They can also be demonstrated in the decidua of women and are probably caused by the action of endogenous oestrogens. Prevailing disturbance of the decidua basalis suggests a production of gestagen in the placenta not only in man but also in the rabbit. Morphologically corresponding transformations are also observed without the administration of oestrogens after laparotomy and particularly after injections into the aorta, as well as in relation to a generalized Shwartzman-Sanarelli-reaction. However, a disturbance of blood coagulation does not occur. Histamine alone does not seem to cause similar transformations. Antihistamines used in this way do not prevent the disturbance caused by oestradiol. The possibility that other vasoactive substances or a local effect of oestradiol can cause interruption of pregnancy is discussed.