Abstract
The distribution and activities of 5-unsaturated-3β- and 17β-hydroxysteroid dehydrogenases (HSD) have been studied during the pregnancy of normal and ovariectomized rats on days 17, 19 and 21 post coitum. No hormonal substitution was provided after bilateral ovariectomy on day 15 post-coitum. 5-Unsaturated-3β-HSD was characterized with pregnenolone, 17α-hydroxypregnenolone and dehydroepiandrosterone as substrates; oestradiol-17β and testosterone were used for the investigation of 17β-HSD activity. With these substrates, it was found that the placental and adrenal activities and distribution of 5-unsaturated-3β-and 17β-HSD did not differ in ovariectomized and control rats and it is suggested that increased placental or adrenal steroidogenesis does not supplement deficient ovarian function in order to maintain pregnancy. In the pregnant rat, the ovaries do not control the activities of 5-unsaturated-3β- and 17β-HSD in the placenta.