ANGIOTENSIN-II RECEPTOR IN HUMAN PLACENTAL SYNCYTIOTROPHOBLAST PLASMA-MEMBRANES

Previous studies have reported the presence of high-affinity angiotens in II (Ang II) binding sites in human placental tissue, but it has not been determined whether these are located in brush border (BBM) or ba solateral plasma (BPM) membranes of the syncytiotrophoblast. Our findi ngs provide no evidence for Ang II receptors in BBM, yet they reveal a single class of binding sites in BPM preparations (K-d of 4.08+/-0.61 nM and B-max of 2368.7+/-658.2 fmol/mg protein). Pharmacological char acterization also revealed that this receptor was an AT(1) receptor su btype. Moreover, isoelectric focusing analysis demonstrated a predomin ant Ang II-receptor complex migrating to pI 7.0, and two minor recepto rs at pI 7.2 and 6.5. These data suggest a physiological role of the r enin-angiotensin system on syncytiotrophoblast BPM in regulating place ntal function.