AUTORADIOGRAPHIC LOCALIZATION AND CHARACTERIZATION OF ANGIOTENSIN-II RECEPTORS IN THE BOVINE PLACENTA AND FETAL MEMBRANES

Autoradiography and angiotensin (Ang) II receptor binding studies show ed that all parts of the bovine placenta and fetal membranes contained high densities of Ang II receptors throughout gestation. The receptor s were predominantly subtype 2 (AT(2)) receptors in the fetal and subt ype 1 (AT(2)) receptors in the maternal compartment. In the allantoamn ionic membrane, Ang II receptors were evenly distributed in the mesenc hymal tissue, with the highest expression around the few arteries. In the intercotyledonary and cotyledonary allantochorionic membrane, AT(2 ) receptors as well as the less-expressed AT(2) receptors were located on mesenchymal cells, especially adjacent to the allantoic endoderm, trophoblast cell layer, and arteries. In the mesenchymal tissue of the placentome, Ang II receptors were mostly expressed at the main branch es of the fetal villi of the cotyledons. In the maternal part of the p lacentome, mainly AT(1) receptors but also low densities of AT(2) rece ptors and non-AT(1)/non-AT(2) Ang II binding sites were found close to the stalk and at the main branches of the maternal crypts. Autoradiog raphy revealed no changes in the pattern of distribution of the Ang II receptors throughout gestation. It is suggested that Ang II has an ef fect on regulatory as well as growth processes in these tissues.