Oxytocin modulates steroidogenesis-associated genes and estradiol levels in the placenta

Background: Oxytocin (OXT) plays a significant role during pregnancy, especially toward the end of pregnancy. Some studies have reported that OXT is involved in the stimulation of steroidogenesis in several organs. However, the effects of OXT on placental steroidogenesis have not yet been established. Methods In this study, we investigated the regulation of steroid hormones and steroidogenic enzymes by OXT-associated signaling in vitro and in vivo by western blotting analysis, ELISA and immunocytochemical analysis. Results OXT increased the gene expression of steroidogenic enzymes, which convert pregnenolone to progesterone and dehydroepiandrosterone (DHEA) in vitro . In OXT-administered pregnant rats, pregnenolone and DHEA levels were significantly enhanced in the plasma by 2.73-fold and 1.53-fold, respectively and the expression of the enzymes synthesizing DHEA, testosterone, and estradiol (E2) was increased in placental tissues. Furthermore, OXT was found to affect placental cell differentiation, which is closely related to steroid hormone synthesis. After treatment of the pregnant rats with atosiban, an antagonist of the OXT receptor, the concentration of E2 in the plasma and the expression of E2-synthesizing enzyme were reduced 1.71-fold and 2.38-3.16-fold, respectively. This regulation may be due to OXT-mediated differentiation, because OXT increases the expression of corticotropin-releasing hormone, which is a biomarker of placental cell differentiation. Conclusions Our findings suggest that OXT regulates the differentiation of placental cells, expression of steroidogenic enzymes in the placenta, and production of critical steroid hormones during pregnancy, and it contributes to the maintenance of pregnancy.