Effects of pregnancy, hypertension and nitric oxide inhibition on rat uterine artery myogenic reactivity.
OBJECTIVE
The purpose of this study was to examine the effects of hypertension and nitric oxide (NO) inhibition on myogenic tone in uterine arteries during pregnancy.


METHODS
Premyometrial radial uterine arteries from nonpregnant and late pregnant Sprague-Dawley rats were evaluated for myogenic reactivity from the following groups: control, hypertensive/NO-inhibited (L-NAME treatment) and normotensive/NO-inhibited (L-NAME plus hydralazine).


RESULTS
In both nonpregnant and pregnant animals, L-NAME treatment significantly elevated blood pressures, while the addition of hydralazine made the animals normotensive. In nonpregnant animals, little myogenic tone was seen in controls; tone increased significantly in the L-NAME group, and was attenuated in those treated with L-NAME plus hydralazine. In pregnant animals, controls developed significant tone; this was reduced in the L-NAME group, and returned to control levels in the L-NAME plus hydralazine group.


CONCLUSIONS
Dimensional measurements showed that arteries from the pregnant hypertensive group did not undergo expansive remodeling, suggesting that tone development is related to phenotypic alterations in vascular smooth muscle and/or altered physical forces secondary to adaptive changes in arterial diameter. These differences implicate pregnancy-specific pathways in the development and inhibition of myogenic tone, and point to potentially opposing roles of NO and hypertension.
Barron
Carolyn
C
Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Vermont College of Medicine, Burlington, VT 05405, USA.
Mandala
Maurizio
M
Osol
George
G
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006830:Hydralazine / Q000494:pharmacology; D006973:Hypertension / Q000201:enzymology / Q000503:physiopathology*; D046110:Hypertension, Pregnancy-Induced; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D055988:Uterine Artery / Q000187:drug effects* / Q000201:enzymology / Q000503:physiopathology*; D014661:Vasoconstriction / Q000187:drug effects*; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D004791:Enzyme Inhibitors; D014665:Vasodilator Agents; D006830:Hydralazine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester