title: Effect of prostaglandin I2 on ovine placental vasculature.
abstract: The response of the placental circulations to prostaglandin I2 (maternal dose 20 microgram/kg, fetal dose 180 microgram/kg) was observed in 10 near-term sheep with chronically implanted vascular catheters. The blood flows before and 90 s after the injection of prostaglandin I2 were measured using radioactive microspheres. The injection of prostaglandin I2 to the mother decreased th blood pressure from 109 +/- 4 to 69 +/- 5 mmHg (P < 0.001) and increased the vascular resistance of the maternal cotyledons from 0.166 +/- 0.018 to 0.209 +/- 0.02 mmHg/(ml/min) (P < 0.001). The vascular bed of the non-cotyledonary uterus vasodilated as the resistance fell from 0.705 +/- 0.02 to 0.266 +/- 0.02 mmHg/(ml/min). (P < 0.001). Prostaglandin I2 caused the fetal arteriovenous pressure to fall from 37.6 +/- 1.35 to 26.0 +/- 1.6 mmHg. There was no significant change in the vascular resistance of the fetal cotyledons. We observed vasodilation in the fetal membranes as vascular resistance fell from 1.06 +/- 0.14 to 0.75 +/- 0.10 mmHg/(ml/min) (P < 0.001). The infusion of prostaglandin I2 significantly depressed the response of the placenta and uterus to norepinephrine. We have not proved that prostaglandin I2 plays a direct role in maintaining placental vascular homeostasis but it may modulate the response of this organ to exogenous vasoactive agents.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D011464:Epoprostenol / Q000494:pharmacology*; D005260:Female; D008863:Microspheres; D010920:Placenta / Q000098:blood supply*; D011247:Pregnancy; D011453:Prostaglandins / Q000494:pharmacology*; D011868:Radioisotopes; D012039:Regional Blood Flow; D012756:Sheep / Q000502:physiology; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D011453:Prostaglandins; D011868:Radioisotopes; D011464:Epoprostenol