Dose-response curves of the uterine and placental vascular beds to prostaglandin I2.
Local infusion of prostaglandin I2 (PGI2) has been reported to dilate the uteroplacental vasculature in a dose-dependent manner. In this experiment we attempted to distinguish the placental and nonplacental (uterine) components of this response over four concentrations of PGI2. Eleven near-term sheep were chronically instrumented for determination of regional blood flows by the use of radioactive microspheres. PGI2 was administered in a retrograde manner via a branch of the middle uterine artery at 1, 3, 10, and 20 micrograms/min. Flows were measured before (control) and after 5-minute infusions at each of the four concentrations (test). The uterine vasculature vasodilated in response to local PGI2 infusion. The 10 micrograms/min dose, for example, produced a mean (+/- SEM) flow of 0.70 +/- 0.07 ml/min/gm; the control value was 0.41 +/- 0.03 ml/min/gm (p less than 0.001). At 20 micrograms/min the test and control flows were 0.75 +/- 0.16 and 0.36 +/- 0.06 ml/min/gm (p less than 0.05), respectively. Uterine vascular resistance fell in a dose-dependent manner as well. There was no evidence of placental vasodilation at any of the doses tested. Renal vasodilation and decreased systemic arterial pressure at higher PGI2 doses suggest a recirculation effect. We conclude that PGI2 does not dilate the placental vasculature over the dose range of 1 to 20 micrograms/min and that the reported vasodilation of the uteroplacental vasculature is a result of decreased resistance in the uterine vasculature alone.
Hollister
M C
MC
Department of Obstetrics-Gynecology, University of Wisconsin, Madison.
Reid
D L
DL
Phernetton
T M
TM
Landauer
M
M
Rankin
J H
JH
D000818:Animals; D001158:Arteries; D001794:Blood Pressure / Q000187:drug effects; D001808:Blood Vessels / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D055590:Electromagnetic Phenomena; D011464:Epoprostenol / Q000494:pharmacology*; D005260:Female; D008863:Microspheres; D010920:Placenta / Q000098:blood supply / Q000187:drug effects*; D012039:Regional Blood Flow / Q000187:drug effects; D012212:Rheology; D012756:Sheep; D014599:Uterus / Q000098:blood supply / Q000187:drug effects*
D011464:Epoprostenol