title: Steroid metabolism by rabbit embryos: time of onset of steroidogenic activity.
abstract: Twenty four hour incubations of the days 5 and 6 pre-implantation and the days 7 and 8 post-implantation rabbit embryos were carried out in the presence of 3H-labelled steroid substrates viz. dehydroepiandrosterone (DHEA), androstenedione (Ad) and testosterone (Te). While both the pre- as well as the post-implantation embryos were able to actively metabolize the various neutral steroid substrates into other neutral, mostly 5 alpha-reduced, steroid metabolites, the conversion of DHEA to Ad or that of DHEA, Ad and Te to estrogens was exhibited only by the days 7 and 8 post-implantation embryos. The findings suggest that pre-implantation blastocysts of rabbit lack the potentiality to synthesize steroids and acquire this ability only after implantation.
mesh_terms: D000735:Androstenedione / Q000378:metabolism*; D000818:Animals; D001755:Blastocyst / Q000378:metabolism*; D003687:Dehydroepiandrosterone / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000378:metabolism*; D005260:Female; D011247:Pregnancy; D011817:Rabbits; D013256:Steroids / Q000096:biosynthesis; D013739:Testosterone / Q000378:metabolism*
chemical_list: D013256:Steroids; D013739:Testosterone; D000735:Androstenedione; D003687:Dehydroepiandrosterone