STUDIES ON THE MECHANISM OF NIDATION. XVII. HISTOCHEMICAL ANALYSIS OF DECIDUALIZATION IN THE RAT
ABSTRACT Studies were made on histochemical aspects of uteri induced to decidualize following the application of specific inhibitors of various stages of decidualization: oestrogen antagonist, and antihistamine and following the withdrawal or suppression of progesterone. In all cases decidualization was grossly impaired. Following application of the oestrogen antagonist, decidual foci did not acquire phosphatase activity. Under the influence of an antihistamine, some foci of decidualization were induced, but did not develop. Likewise, when progesterone was withdrawn on the day of induction, decidualization did not take place. Suppression of progesterone when decidualization was already established, either by ovariectomy or by administration of ergocornine, gave histochemically similar results: haemorrhage, leucocytic infiltration, breakdown of decidual tissue with loss of alkaline phosphatase and ATP-ase activities and a rise of acid phosphatase activity. The histochemical findings add support to the postulated mechanism of decidualization which incorporates an oestrogen surge and consequent sensitization of the uterus; a histaminogenic induction of decidualization and progesterone requirement for support. They also confirm the ergocornine disturbance of progesterone status.