Estradiol and progesterone levels in the endometrium and the reproductive tract luminal washing during the pre-implantation stages of gestation in the rhesus monkey.

To obtain an understanding of the sex steroid hormonal milieu during early gestation, the concentrations of estradiol-17 beta and progesterone were measured in endometria and reproductive tract luminal fluids collected during the post-ovulatory period (days 2 to 6) of conception, and of non-mated menstrual cycles of the rhesus monkey (Macaca mulatta). Estradiol content was found to be higher (P less than 0.05) in endometria obtained from conception cycles; day-wise analysis revealed higher (P less than 0.05) level of tissue estradiol concentration on day 6 of post-ovulation as compared with the normal menstrual cycle. Endometrial progesterone content remained, however, unaltered in both groups of monkeys and thus relatively lower (P less than 0.05) endometrial progesterone to estradiol ratios were seen on days 4, 5 and 6 of gestation compared with normal menstrual cycle. There were no significant changes in the profiles and concentrations of estradiol and progesterone in luminal washings. The typical sex steroid hormonal milieu observed in the endometrium during the peri-implantation stage of gestation in conception cycle may be related to the endometrial differentiation towards implantation in the rhesus monkey.