Angiotensin II Stimulates Both Inositol Phosphate Production and Human Placental Lactogen Release from Human Trophoblastic Cells

ABSTRACT We studied the functional significance of the binding of angiotensin-II (All) to human placentas. Human trophoblastic cell suspensions were prepared by trypsin digestion of minced tissue. Cell incubations with increasing doses of [125I] (Sar1)AII, ranging from 0.01–2.5 nmol/L, were carried out for 20 min at 37 C. The results indicated the presence of specific low capacity [4300 ± 1300 (±SE) sites/cell], high affinity (Kd = 0.38 ± 0.06 nmol/L) binding sites for [125I](Sar1)AII. This binding was specific for All analogs. When placental cells were preloaded with 40 μCi/mL [3H]myoinositol for 2 h at 37 C, AH stimulation resulted in a dose-dependent increase in inositol phosphate (InsP) production [EC50 = 1.4 ± 0.4 (±SE) nmol/L], as measured by ion exchange chromatography. (Sar1)AII also stimulated InsP production, with an EC50 of 0.3 ± 0.2 nmol/L. All-stimulated production of InsP was completely blocked by the antagonist (Sar1,Ala8)AII. All also stimulated human placental lactogen release from tropho...