TEMPORARY INTERRUPTION OF THE MORPHOGENESIS OF DECIDUOMATA IN THE MOUSE UTERUS BY ACTINOMYCIN D

Summary. A single injection of 15 μg actinomycin D on Day 5 after mating interrupted pregnancy in five/five mice. To obtain information about the mode of action of the drug, its effect on the progress of the artificial decidual cell reaction was studied. Ovariectomized mice were prepared for decidualization with exogenous hormones and decidualization induced by the intrauterine injection of arachis oil. Intraperitoneal injection of actinomycin D 7½ or 1½ hr before the decidual stimulus did not prevent the early stages of the decidual reaction but delayed by 24 to 30 hr the onset of decidual transformation of the stromal cells. It appears that the drug blocks the chain of reactions leading to decidual morphogenesis after the initiation of the reaction but that once the effect of the drug wears off, development of the decidua resumes provided the hormone conditions are adequate.