The secretion of hormones during the culture of human preimplantation embryos with corona cells.

Following in vitro fertilization of human preovulatory oocytes from spontaneously ovulating women, determinations were made of the secretion into the culture medium of progesterone, estradiol, human chorionic gonadotropin (hCG), and the prostaglandins (PG) E2 and F2 alpha, over a 3- to 4-day period of embryo development. It was found that the corona cells associated with the egg could account, between days 2 and 3, for a mean daily secretion of 50 ng of progesterone and approximately 100 pg of estradiol, PGE2, and PGF2 alpha, respectively. Mechanical removal of the corona cells after about 48 hours for the examination of the egg for cleavage reduced the mean amount of progesterone produced on day 3 to 2 ng, and a concomitant decrease in estradiol. PGE2, and PGF2 alpha was observed. Steroid secretion could be restored on day 3 to more than 50% of that secreted on day 2 by returning some detached corona cells to the culture medium containing the embryo. hCG was not detected (less than 2 mIU/ml) in the culture medium at any stage of embryo culture over the 3- to 4-day period.