Abstract Body: Introduction: Pregnancy induces significant cardiovascular adaptations, such as increased cardiac output and reduced vascular resistance, to support fetal development and maintain maternal homeostasis. After pregnancy, the vasculature remodels back to pre-pregnancy status. The mechanisms driving this process in peripheral arterial beds remain poorly understood. Mesenteric arteries are of special interest because they play a crucial role in regulating systemic vascular resistance and accommodating the increased blood flow during pregnancy.
Hypothesis: In this study we test the hypothesis that pregnancy induces mechanical adaptation in third-order mesenteric arteries (MAs) and that these changes will return to baseline 10 days postpartum.
Methods: We performed mechanical testing of MAs from nulliparous (NP, n=4), day 20 of gestation (P20, n=4), and 10 days postpartum (PP10, n=3) Long-Evans rats. We assessed key parameters – inner diameter (d_i), percent tone (%T), and stress induced by vascular smooth muscle cells (△stress) – for a range of pressures (20-120 mmHg) under active (assessing myogenic tone), passive (assessing contribution of the extracellular matrix), and phenylephrine (PE)-stimulated (assessing sympathetic response) conditions.
Results and Conclusions: Pregnancy increased luminal diameter under both active and PE-stimulated conditions to accommodate increased blood flow, aligning with predictions that arterial remodeling maintains homeostatic wall shear stress during pregnancy (Fig. 1A and 1C). Arteries in the P20 group also exhibited reduced myogenic tone and decreased stress induced by vascular smooth muscle cells at higher pressures (Fig. 2A and 2C), indicating the artery’s diminished ability to contract in response to pressure. By 10 days postpartum, vascular responses returned to pre-pregnancy levels across all measured parameters. These findings offer valuable insights into the vascular adaptations of pregnancy and postpartum recovery, with important implications for understanding maternal vascular health.