Nitric oxide is involved in flow-induced dilation of isolated human small fetoplacental arteries
Article Abstract:
Increased blood flow during pregnancy may stimulate the release of nitric oxide in the blood vessels of the fetus and placenta. Nitric oxide may be responsible for maintaining low vascular resistance during normal pregnancies. Researchers connected small arteries from normal, delivered placentas to a device that varied flow pressure. Some arteries were exposed to a nitric oxide inhibitor; others were not. Increased flow pressure caused arteries to dilate, but the nitric oxide inhibitor reduced arterial dilation. The reduction in dilation caused by the nitric oxide inhibitor was greatest during initial flow increases, with dilation increasing a bit with later flow increases. Abnormal umbilical arteries may reduce placental blood flow even though nitric oxide is produced. Preeclampsia may reduce nitric oxide production.
Publication Name: American Journal of Obstetrics and Gynecology
Subject: Health
ISSN: 0002-9378
Year: 1996
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Myogenic and flow-mediated responses in isolated mesenteric small arteries from pregnant and nonpregnant rats
Article Abstract:
Reductions in muscle fiber constriction in pregnancy may not reduce blood vessel resistance. The stress on blood vessels caused by increased flow, or shear stress, may trigger the release of nitric oxide which in turn causes small arteries to relax. Researchers measured responses of muscle fibers from pregnant and nonpregnant rats to pressure and to vasoconstricting and vasodilating substances. Muscle fibers from pregnant rats exhibited reduced constriction, but this did not seem to reduce blood vessel resistance. Increases in shear stress increased the release of nitric oxide, causing vasodilation in muscles from pregnant rats. Increases in nitric oxide release induced by shear stress during pregnancy may cause blood vessels to dilate and reduce their resistance.
Publication Name: American Journal of Obstetrics and Gynecology
Subject: Health
ISSN: 0002-9378
Year: 1996
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17 beta-estradiol stimulates flow-induced vasodilatation in isolated small mesenteric arteries from prepubertal female rats
Article Abstract:
Relaxation of arteries during pregnancy may be induced by an estrogen hormone. Researchers tested the effect of estradiol hormones on arteries harvested from rats. When treated with the hormone 17 beta-estradiol, arteries relaxed and increased in diameter as the rate of fluid flowing through them was increased. This vascular dilation was in response to concentrations of 17 beta-estradiol typically present during pregnancy. This effect may contribute to the fall in diastolic blood pressure during pregnancy, and may improve uterine blood flow.
Publication Name: American Journal of Obstetrics and Gynecology
Subject: Health
ISSN: 0002-9378
Year: 1997
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