THE COMPARATIVE EFFECTS OF PROGESTERONE, ESTRADIOL, DIETHYLSTILBESTROL ANDITS MONOMETHYL ETHER ON THE EARLY BLASTOCYST OF THE RABBIT1

Abstract

THE SIZE of the 5 day rabbit blastocyst has been shown to be function of theamount of progesterone administered (Pincus & Werthessen, 1937). It was further demonstrated that the simultaneous injection of natural or synthetic estrogens profoundly altered the degree of response to a fixed dose of progesterone (Pincus & Wer-thessen, 1938). Thus, estradiol and estriol appeared to stimulate the growth of the blastocyst further, while estrone definitely inhibited it. The response of the endometrium differed from that of the blastocyst, in that estriol, for example, produced in the same rabbit a significant increment in blastocyst size and a notable diminution in endometrial responseto the standard dose of progesterone, estradiol produced significant increments in both blastocyst size and endometrial growth within the lower concentrations of the dosage employed, while the higher concentrations resulted only in significant increases in blasto-cyst size; the endometrial response was essentially that of the controls.