Steroidal Aspects of Pregnane Inhibition of Progesterone in Decidual Development

¹ From the Department of Anatomy, Yale University School of Medicine, New Haven, Connecticut

Previously, Hisaw, Velardo and Ziel (1954) reported that several of the pregnanediols inhibited decidual development in progesterone-treated, ovariectomized pseudopregnant rats. The present report is an attempt to ascertain the modus operandi of this decidual inhibition. Utilizing three experimental designs, it has been ascertained that both pregnane 3 , 20 ß diol, and pregnane 3 ß, 20 ß diol modify the response of the traumatized uterus of the ovariectomized rat to progesterone; consequently, a reduction in decidual tissue results. These experiments further show that the initial estradiol-17 ß action is not opposed, nor is the growth response of the uterus of the ovariectomized rat interfered with by the concurrent administration of estradiol-17 ß and either one of the two pregnane compounds under investigation. These data indicate that 1) the inhibition of decidual tissue is the result of the action of these pregnanes on progesterone activity, and 2) these compounds do not alter the response of the uterus and the vagina of the ovariectomized rat to estradiol-17 ß