Production and Metabolism of Progesterone and Androstenedione by Cultured Mouse Blastocysts

Abstract

Mouse preimplantation embryo and postblastocyst cultures were assayed for their ability to produce and utilize progesterone and androstenedione. We were unable to detect the conversion of pregnenolone to progesterone by cultured preimplantation embryos, from two-cell to blastocyst. This appears not to have been due to problems with permeability. With further culture, after the blastocysts have attached to the surface of the dish and trophoblast outgrowth has taken place, progesterone is produced. Similar observations were made concerning the utilization of progesterone, as well as the formation and further metabolism of androstenedione. These results suggest that Δ⁵ ,3β-hydroxysteroid dehydrogenase activity, and other enzyme activities involved in progestin and androgen metabolism, are only acquired by postimplantation conceptuses. This would negate the possibility that steroid biosynthesis by the mouse blastocyst is involved in its implantation.