Increased Myogenic Reactivity of Resistance‐sized Mesenteric Arteries from Pregnant Rats with Episodic Reductions in Uteroplacental Perfusion

Abstract

Pregnancy is associated with increased placental blood flow (BF) to the developing fetus. A central component of preeclampsia is thought to be a reduction in placental BF leading to altered vascular reactivity. It is suggested that short term elevations in blood pressure may lead to periodic reductions in uteroplacental blood flow (UBF) and this may play a role in preeclampsia. The purpose of this study was to develop a gravid rat model characterized by episodic reductions in UBF to elucidate the role of periodic decreases in UBF on vascular reactivity. We used pregnant Sprague Dawley rats and subjected them to Sham or aortic occlusion surgery on Day 14 of gestation. Aortic occlusion surgery consisted of implantation of a silastic vascular occluder around the abdominal aorta along with silver clips (0.106mm ID) around the uterine‐ovarian arteries. Aortic occlusion animals were subjected to 5 days of reduced UBF (40% reduction) for 1 hour each session. On Day 21, second order mesenteric arteries were mounted on a pressurized arteriograph. Myogenic reactivity of small mesenteric arteries was increased in Occluder animals compared to Sham (p<0.05). This data suggest that episodic reductions in UBF may mimic some of the characteristics of preeclampsia including altered vascular reactivity toward a constrictive phenotype. Aortic occlusion may be a new model for investigating mechanisms associated with reduced UBF.