In the human syncytiotrophoblast, the AT1 receptors were localized on the basolateral plasma membranes. Recent in vitro studies using human trophoblast cells have demonstrated that Ang II stimulated human placental lactogen and specific (31-glycoprotein secretion through the AT receptor. As shown in Figure 8, we found no binding of 125I-[Sar1-Ile5-Ile8]-Ang II to the bovine placental lactogen-producing binucleate and trinucleate cells situated in the trophoblast cell layer and maternal uterine epithelium. This finding suggests that Ang II does not regulate the secretion of placental lactogen in the bovine placenta, in contrast to the findings in the humans. birth control pills
In the bovine species, the Ang II receptors were localized to cells in the mesenchyme of the fetal membranes and were mainly AT2 receptors. The fact that the AT2 receptor predominated in the fetal compartment of the bovine placenta and the finding that the density of the Ang II receptor decreased at the end of the gestation suggest that the function of RAS in the bovine placenta differs from that in humans. In the rodent and primate fetus, the presence of abundant Ang II binding sites has been found in locations at which Ang II binding is not observed in the adult.