PREGNANCY-INDUCED CHANGES IN THE 3-DIMENSIONAL MECHANICAL-PROPERTIES OF PRESSURIZED RAT UTEROPLACENTAL (RADIAL) ARTERIES

OBJECTIVE: The purpose of this study was to describe the effects of pregnancy on the size and three-dimensional mechanics of uterine radial arteries. STUDY DESIGN: Measurements of lumen diameter, wall thickness, and axial and radial distensibility were made in situ and in pressurized segments of excised vessels from nonpregnant (n = 29) and late-pregnant (days 19 to 21, n = 19) Sprague-Dawley rats. RESULTS: In the unpressurized state, the overall length of the radial artery segment of the arcade increased approximately 4.8 times during gestation. Lumen diameter increased by 60%, as did distensibility in both the radial and axial directions. However, there was no measurable change in the thickness of the vascular wall, which was muscular in appearance and comprised approximately two layers of circumferentially oriented smooth muscle, a relatively thick internal elastic lamina, and a well-defined endothelial layer. Cross-sectional area increased significantly during pregnancy (1.37 times at 50 mm Hg), as did the overall volume of the vascular wall (6.86 times at 50 mm Hg), primarily as a result of arterial growth in the longitudinal (axial) direction. CONCLUSIONS: Remodeling of the radial artery segment of the uterine vasculature clearly occurs during gestation, resulting in vessels that are of a larger caliber and are longer and more distensible in both the axial and radial directions.