Effects of blockade of the endothelin receptor A and inhibition of nitric oxide synthesis on uteroplacental and renal blood flow in awake pregnant rats.
OBJECTIVE
The aim of this study was to evaluate the role of the ETA receptor and nitric oxide (NO) in the regulation of uteroplacental and renal blood flow in pregnant rats.


METHODS
Regional blood flows were measured by the microsphere technique in pregnant Sprague-Dawley rats (term 23 days). Blood flow was measured before and after ETA receptor blockade (BQ-123, 1 mg/kg) at gestational day (GD) 19 or 21 (n=8 and n=9, respectively). In 2 additional groups blood flow was measured before and after NO synthase inhibition (L-NAME 2 microg/min) at GD 19 or 21 (n=10 in each group).


RESULTS
BQ-123 significantly increased placental and myometrial blood flows by almost 80% and 35%, respectively, at both gestational ages. BQ-123 did not alter renal blood flow. No effect on placental or myometrial blood flow was observed after L-NAME infusion, neither at GD 19 nor GD 21. Renal blood flow decreased by nearly 35% in both groups after L-NAME.


CONCLUSIONS
There is an important role for endogenous ET in the regulation of uteroplacental blood flow in the rat. NO contributes to a significant vasodilatation in the renal vasculature; however, NO appears not to be involved in the maintenance of uteroplacental blood flow in the awake pregnant rat.
Ajne
Gunilla
G
Department of Obstetrics and Gynecology, Karolinska University Hospital Huddinge, Karolinska Institute, Stockholm, Sweden. gunilla.ajne@kus.se
Nisell
Henry
H
Jansson
Thomas
T
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D065128:Endothelin Receptor Antagonists; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007668:Kidney / Q000098:blood supply / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D010456:Peptides, Cyclic / Q000494:pharmacology*; D010920:Placenta / Q000098:blood supply / Q000187:drug effects*; D011247:Pregnancy; D011673:Pulsatile Flow; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow
D000959:Antihypertensive Agents; D065128:Endothelin Receptor Antagonists; D004791:Enzyme Inhibitors; D010456:Peptides, Cyclic; D019001:Nitric Oxide Synthase; C072247:cyclo(Trp-Asp-Pro-Val-Leu); D019331:NG-Nitroarginine Methyl Ester