Effect of PGI2 on the response of the ovine placenta to norepinephrine.
We have examined the effects of PGI2, 50 microgram/kg, on norepinephrine induced placental vasoconstriction in 6 chronically catheterized near-term sheep. Regional blood flows were measured with radioactive microspheres. Control flows were measured. Norepinephrine was than infused at 50 microgram/min throughout the experiment. After 15 min the blood flows were again measured and PGI2 was then added to the infusate at 50 microgram/min. In 15 min regional blood flows were again measured and the PGI2 infusion was stopped. Regional blood flows were measured for the last time 15 min later. The renal and nonplacental uterine vasculatures behaved in a predictable manner. There was constriction with norepinephrine but PGI2 opposed the effects of norepinephrine and decreased the resistance towards the normal levels. The placenta did not behave as did the other organs. Norepinephrine increased placental resistance but PGI2 did not decrease the resistance and severely depress the placental blood flows. PGI2 does not appear to oppose norepinephrine induced placental vasoconstriction.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D011464:Epoprostenol / Q000494:pharmacology*; D005260:Female; D007668:Kidney / Q000098:blood supply; D009638:Norepinephrine / Q000494:pharmacology*; D010920:Placenta / Q000098:blood supply* / Q000187:drug effects; D011247:Pregnancy; D011453:Prostaglandins / Q000494:pharmacology*; D012039:Regional Blood Flow / Q000187:drug effects; D012756:Sheep; D014599:Uterus / Q000098:blood supply; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects
D011453:Prostaglandins; D011464:Epoprostenol; D009638:Norepinephrine