Differential effects of endothelin A and B receptor antagonism on fetal growth in normal and nitric oxide-deficient rats.
OBJECTIVE
To determine the role of endothelin (ET) in fetal and placental growth in rats with and without long-term nitric oxide synthase (NOS) inhibition.


METHODS
Pregnant rats were treated with N(omega)-nitro-L-arginine methyl ester (L-NAME) or saline and with one of three ET receptor antagonists or vehicle. The antagonists included A-182086 (nonselective) as well as A-127722 and FR-139317 (both ET(A) selective). Treatment was begun on day 14 of gestation. On gestational day 21, a hysterotomy was done. Litter size was recorded, and viability and fetal and placental weights were determined. Results were analyzed by analysis of variance or by a Kruskal-Wallis nonparametric analysis.


RESULTS
In the absence of L-NAME, fetal and placental weights were not affected by ET(A)-selective antagonism but were significantly decreased by nonselective receptor antagonism (P <.001 and P <.05 for fetal and placental weights, respectively). Infusion of L-NAME resulted in fetal and placental growth restriction (P <.001). In the setting of L-NAME infusion, fetal and placental weights were increased by the ET(A)-selective antagonists (P <.01) but not by the nonselective antagonist, compared with weights from animals treated with L-NAME alone. There were more fetal deaths with L-NAME treatment (P <.05), but their occurrence was not significantly affected by any of the ET receptor antagonists.


CONCLUSIONS
Endothelin-A antagonism alone did not affect fetal or placental growth, whereas combined ET(A) plus ET(B) antagonism produced fetal and placental growth restriction. In the setting of long-term NOS inhibition, ET(A)-selective antagonism improved fetal and placental growth, whereas antagonism of both ET(A) and ET(B) receptors did not. Endothelin contributes to NOS inhibition-induced growth restriction acting through the ET(A) receptor.
Thaete
L G
LG
Division of Maternal-Fetal Medicine, Department of Obstetrics & Gynecology, Northwestern University Medical School, Evanston Northwestern Healthcare, 2650 Ridge Avenue, Evanston, IL 60201, USA.
Neerhof
M G
MG
Silver
R K
RK
D000818:Animals; D000077868:Atrasentan; D001381:Azepines / Q000494:pharmacology; D005314:Embryonic and Fetal Development / Q000187:drug effects*; D065128:Endothelin Receptor Antagonists; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005317:Fetal Growth Retardation / Q000139:chemically induced; D007211:Indoles / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000172:deficiency* / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010920:Placenta / Q000187:drug effects / Q000502:physiology; D011247:Pregnancy; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000502:physiology
D001381:Azepines; D065128:Endothelin Receptor Antagonists; D004791:Enzyme Inhibitors; D007211:Indoles; D011759:Pyrrolidines; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; C079574:FR 139317; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester; D000077868:Atrasentan