STUDIES ON THE MECHANISM OF DECIDUALIZATION. V.
ABSTRACT The uteri of pseudopregnant rats show a peak of metabolic activity on the 4th and 5th day of leucocytic smear. After the administration of 20 mg of pyrathiazine Cl on the 4th day of pseudopregnancy (L4) in order to induce decidualization of the progestational endometrium, the metabolic activity of the uterus becomes intensified. The amount of synthesis, estimated by determinations of uterine weight, and amount of protein and nucleic acids, was considered as being related to an oestrogen surge occurring on the 3rd day. The present work was undertaken to confirm the relation between the oestrogen surge and the metabolic activity found in the uterus thereafter by using an antioestrogenic substance: ethanoxytriphetol (MER-25). The experiments were performed in pseudopregnant as well as in decidualizing animals. MER-25 was injected on the 3rd day of leucocytic vaginal smear of pseudopregnancy. Analyses of the uterine components 24, 48, 72, 96 h after the injection of the antioestrogen showed a definite inhibition of the synthetic processes in the uterus of the otherwise untreated pseudopregnant rat as well as in decidualizing uterus. The results, confirm the role of oestrogen surge in the processes of decidualization and the close relationship between the oestrogen surge, increase of metabolism and decidualization.