Changes in Ovarian and Placental 20α-hydroxysteroid Dehydrogenase Activity during the Pregnancy in the Rat

The enzyme 20α-hydroxysteroid dehydrogenase (20α-HSD) catabolizes progesterone to 20α-dihydroprogesterone (20α-OHP), and is appeared in rat corpora luteal and placenta. A polled samples of 10-15 placental and ovarian tissues collected from each individual rat were subjected to measurement of 20α-HSD activity. A 20α-HSD activity in the cytosol fraction was based on the generation of NADPH. In this study, it is designed to study cytosolic 20α-HSD activity in rat ovarian and placenta during pregnancy, and its relationship to embryonic mortality. It was found that from days 5 to 18 of pregnancy the 20α-HSD activities steady by decreased but at parturition time rapidly increased in ovary. On the other hand, placental cytosolic 20α-HSD activities were high detected from days 8 to 10 of pregnancy, not detectable from days 11 to 20 of pregnancy, but again very high at the time of parturition. Analysis of DEAE column chromatography revealed that two different types of 20α-HSD (HSD-1 and HSD-2) were found with similar activity in the placental cytosol on day 10 of pregnancy. The number of fetuses on day 10 of pregnancy was 15.4 and decreased significantly to 12.9 on day 12. The results suggested that expression of 20α-HSD in the placental tissues seems to be related the number of fetal survived in the specific time (days 11 and 12) which spontaneous fetal loss occurs. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 3 : 342-347)