title: Maternal vascular responses to hypoxia in a rat model of intrauterine growth restriction.
abstract: Intrauterine growth restriction (IUGR) is a common pregnancy complication and is a leading cause of fetal morbidity and mortality. Placental hypoxia contributes to adverse fetal consequences, such as IUGR. Exposing pregnant rats to hypoxia can lead to IUGR; however, assessment of maternal vascular function in a rat model of hypoxia, and the mechanisms that may contribute to adverse pregnancy outcomes, has not been extensively studied. We hypothesized that exposing pregnant rats to hypoxia will affect maternal systemic vascular function and increase the uterine artery resistance index (RI), which will be associated with IUGR. To test this hypothesis, pregnant rats were kept in normoxia (21% O2) or hypoxia (11% O2) from gestational day (GD) 6 to 20 Maternal blood pressure, uteroplacental resistance index (RI) (ultrasound biomicroscopy), and vascular function (wire myography) were assessed in uterine and mesenteric arteries. Fetal weight was significantly reduced (P < 0.001), while maternal blood pressure was increased (P < 0.05) in rats exposed to hypoxia. Maternal vascular function was also affected after exposure to hypoxia, including impaired endothelium-dependent vasodilation responses to methacholine in isolated uterine arteries (pEC50normoxia: 6.55 ± 0.23 vs. hypoxia: 5.02 ± 0.35, P < 0.01) and a reduced uterine artery RI in vivo (normoxia: 0.63 ± 0.04 vs. hypoxia: 0.53 ± 0.01, P < 0.05); associated with an increase in umbilical vein RI (normoxia: 0.35 ± 0.02 vs. hypoxia: 0.45 ± 0.04, P < 0.05). These data demonstrate maternal and fetal alterations in vascular function due to prenatal exposure to hypoxia. Further, although there was a compensatory reduction in uterine artery RI in the hypoxia groups, this was not sufficient to prevent IUGR.
authors.affiliation: Department of Obstetrics and Gynecology, University of Alberta, Alberta, Edmonton, Canada.|Department of Physiology, University of Alberta, Alberta, Edmonton, Canada; and.|Women and Children's Health Research Institute and the Cardiovascular Research Centre, Edmonton, Alberta, Canada.
authors.forename: Mais M
authors.initials: MM
authors.lastname: Aljunaidy
authors.affiliation: Department of Obstetrics and Gynecology, University of Alberta, Alberta, Edmonton, Canada.|Women and Children's Health Research Institute and the Cardiovascular Research Centre, Edmonton, Alberta, Canada.
authors.forename: Jude S
authors.initials: JS
authors.lastname: Morton
authors.affiliation: Department of Obstetrics and Gynecology, University of Alberta, Alberta, Edmonton, Canada.|Women and Children's Health Research Institute and the Cardiovascular Research Centre, Edmonton, Alberta, Canada.
authors.forename: Christy-Lynn
authors.initials: CL
authors.lastname: Cooke
authors.affiliation: Department of Obstetrics and Gynecology, University of Alberta, Alberta, Edmonton, Canada; sandra.davidge@ualberta.ca.|Department of Physiology, University of Alberta, Alberta, Edmonton, Canada; and.|Women and Children's Health Research Institute and the Cardiovascular Research Centre, Edmonton, Alberta, Canada.
authors.forename: Sandra T
authors.initials: ST
authors.lastname: Davidge
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity; D001794:Blood Pressure; D005260:Female; D005317:Fetal Growth Retardation / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008638:Mesenteric Arteries / Q000503:physiopathology*; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D055988:Uterine Artery / Q000503:physiopathology*; D014655:Vascular Resistance
keywords: hypoxia; intrauterine growth restriction; ultrasonography; uterine artery; wire myography