Effects of pregnancy on femoral microvascular responses in the rat.
OBJECTIVE
Our purpose was to test the hypothesis that augmented basal and vasodilator agonist-stimulated synthesis of endothelium-derived nitric oxide would blunt vasoconstrictor-induced contraction and enhance relaxation in isolated femoral resistance vessels from pregnant rats.


METHODS
Potassium chloride-, phenylephrine-, and angiotensin II-induced contraction and acetylcholine-induced relaxation were assessed in small (approximately 240 microns diameter) femoral resistance arteries from gravid and virgin animals studied under isometric conditions; the effects of potassium chloride, phenylephrine, and acetylcholine were also studied in the presence of nitroarginine.


RESULTS
Maximal vasoconstriction was similar in vessels from virgin and pregnant rats, whereas phenylephrine potency was slightly enhanced in vessels from gravid animals. Nitroarginine augmented contraction in both groups but with greater effect on phenylephrine potency and on submaximal potassium chloride contractions in virgins. Acetylcholine-induced relaxation did not differ between groups and was similarly, but only partially, inhibited by nitroarginine.


CONCLUSIONS
Pregnancy does not result in vasoconstrictor resistance, increased basal nitric oxide synthesis, or augmented agonist-stimulated endothelium-dependent relaxation in this particular isolated rat microvascular preparation. Further, endothelium-dependent relaxation of these vessels depends only partly on nitric oxide.
Yamasaki
M
M
Department of Medicine, University of Chicago, IL 60637, USA.
Lindheimer
M D
MD
Umans
J G
JG
D000109:Acetylcholine / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D004730:Endothelium, Vascular / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005269:Femur / Q000098:blood supply*; D008833:Microcirculation / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014655:Vascular Resistance; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
D004791:Enzyme Inhibitors; D000804:Angiotensin II; D010656:Phenylephrine; D019335:Nitroarginine; D009569:Nitric Oxide; D011189:Potassium Chloride; D019001:Nitric Oxide Synthase; D000109:Acetylcholine