Formation of steroids by the pregnant mare. V. Metabolism of 14C-isopentenylpyrophosphate and 3H-dehydroisoandrosterone injected into the fetus.
A mixture of 1-14C-isopentenylpyrophosphate and 3H-dehydroisoandrosterone was injected into a horse fetus intramuscularly during laparotomy, after which maternal urine was collected for 4 days. Steroid conjugates in the urine were extracted with Amberlite XAD-2 resin, hydrolysed and separated into phenolic and neutral fractions. From the phenolic fraction estrone, 17alpha-estradiol, equilin and equilenin were isolated. Only estrone and 17alpha-estradiol contained both 3H and 14C, while the ring B unsaturated estrogens contained only 14C. From the neutral fraction 14C-labeled 3beta-hydroxy-5alpha-pregnan-20-one, 5alpha-pregnane-3beta,20beta-diol and 5alpha-pregnan-3beta, 20alpha-diol were isolated. These results demonstrate that the route of biosynthesis of both the ring B saturated and unsaturated estrogens is the same up to the stage of isopentenylpyrophosphate. Thus, the bifurcation in the classical pathway of steroid biosynthesis reported previously by us is occurring at a point after the formation of isopentenylpyrophosphate and prior to the formation of squalene.
D015068:17-Ketosteroids / Q000096:biosynthesis / Q000652:urine; D000475:Alkenes / Q000378:metabolism; D000818:Animals; D003687:Dehydroepiandrosterone / Q000378:metabolism*; D004958:Estradiol / Q000652:urine; D004962:Estranes / Q000096:biosynthesis* / Q000652:urine; D004967:Estrogens / Q000652:urine; D004970:Estrone / Q000652:urine; D005260:Female; D006736:Horses / Q000378:metabolism*; D006914:Hydroxysteroids / Q000652:urine; D008431:Maternal-Fetal Exchange; D009943:Organophosphorus Compounds / Q000378:metabolism*; D010636:Phenols; D010756:Phosphoric Acids / Q000378:metabolism; D011247:Pregnancy; D011270:Pregnancy, Animal; D011276:Pregnanediol / Q000652:urine; D011278:Pregnanes / Q000652:urine
D015068:17-Ketosteroids; D000475:Alkenes; D004962:Estranes; D004967:Estrogens; D006914:Hydroxysteroids; D009943:Organophosphorus Compounds; D010636:Phenols; D010756:Phosphoric Acids; D011278:Pregnanes; D004970:Estrone; D003687:Dehydroepiandrosterone; D004958:Estradiol; D011276:Pregnanediol