VASCULAR ANGIOTENSIN-II AND ATRIAL-NATRIURETIC-PEPTIDE RECEPTORS IN NORMAL AND GROWTH-RETARDED HUMAN PLACENTAE

Receptors for angiotensin II (AII) and atrial natriuretic peptide (ANP) were characterized in a membrane fraction from resistance-type artery from human placentae. Placentae from normal pregnancies and pregnancies complicated by intrauterine growth retardation (IUGR) were studied. High- and low-affinity receptors for AII (dissociation equilibrium constant (K(d)) 1.7 and 15.7 nmol/l respectively) and ANP (K(d) 0.2 and 55.5 nmol/l respectively) were identified; these parameters were unchanged in IUGR, but there was a reduction in high-affinity receptor number by approximately 50% for AII and 80% for ANP in theis condition. Both peptides may have a role in the regulation of fetoplacental blood flow. The alterations in IUGR are consistent with sustained activation of the fetal renin angiotensin system and suggest altered vascular responsiveness to ANP.