Structural remodeling of rat uterine veins in pregnancy.

Objective: This study characterized the cellular remodeling that contributes to uterine venous growth during gestation and evaluated the effect of pregnancy on the mechanical properties of the uterine vein.

Study Design: Diameter and distensibility were calculated in pressurized uterine veins from virgin and pregnant (19-20 days of gestation) rats; the rates of cellular division (endothelial, vascular smooth muscle) were quantified with an intraperitoneal bromodeoxyuridine injection and immunohistochemistry. Elastin content, adrenergic nerve density, and wall thickness were determined in fixed uterine veins and quantified with an imaging program.

Results: There was a statistically significant increase in the diameter and mitotic indices (endothelial, vascular smooth muscle) in uterine veins from late pregnant versus nonpregnant animals. Adrenergic nerve density was diminished significantly during gestation. Venous distensibility increased during pregnancy, with an associated reduction in elastin content.

Conclusion: Pregnancy results in coordinated and multifaceted structural remodeling of uterine veins with subsequent changes in caliber, mechanical properties, rates of cellular division, adrenergic innervation, and matrix composition.