Increased Myogenic Responses of Resistance-Sized Mesenteric Arteries After Reduced Uterine Perfusion Pressure in Pregnant Rats

Abstract

Objective. A central component of preeclampsia is a reduction in utero-placental perfusion. We tested the hypothesis that vascular reactivity of second – order mesenteric arteries would be increased in a pregnant rat with reduced uterine perfusion pressure (RUPP). Methods. Pregnant 10–12 week old Sprague-Dawley rats underwent RUPP surgery on gestational day 14, and experiments were carried out on day 20. SHAM operated animals were used as controls. Resistance caliber mesenteric arteries (200–250 μm) were isolated, myogenic reactivity and responses to vasoconstrictor and vasodilator agonists were assessed utilizing a pressurized arteriograph system. Results. RUPP resulted in maternal hypertension and reductions in fetal number and weight. Resistance caliber mesenteric arteries (200–250 μm) were isolated, myogenic reactivity and responses to vasoconstrictor and vasodilator agonists were assessed utilizing a pressurized arteriograph system. Myogenic reactivity responses were normalized as a percent change in vessel diameter from an initial diameter at 20 mmHg. The mesenteric arteries from RUPP animals exhibited a significant increase in myogenic reactivity compared to SHAM controls (p < 0.05). This increased myogenicity was reversed with prostaglandin inhibition, suggesting a role for a vasoconstrictor prostaglandin. In addition to alterations in myogenic reactivity, resistance-sized arteries from RUPP animals have decreased responses to nitric oxide (NO) as evidenced by decreases in responses to methacholine (ME; P < 0.05) and no change in myogenic reactivity after NO synthase blockade. Conclusion. RUPP alters the behavior of resistance caliber arteries to favor a more contractile phenotype with decreased in NO responses, which is similar to what is seen in preeclampsia.