Umbilical vessels endothelium and vascular reactivity

In vitro preparations of isolated umbilical vessels are ideal for the study of vasoactive substances. These vessels display vascular reactivity in response to numerous substances, although the mechanism of action of many of these agents is unknown. The present study was undertaken to study the role of the endothelium in the vasoactivity of these preparations, and to examine their cellular integrity. Umbilical artery and vein were studied using conventional isometric techniques, and using high power light microscopy. We found that umbilical vessel rings had no relaxant response to agents believed to release endothelium-derived relaxant factor (EDRF). Mechanical and chemical treatment to remove endothelium did not significantly alter vascular response to known contractile agonists. Cellular morphology is well maintained in ring preparations. Finally, mechanical rubbing of the intima of these rings is more reliable in endothelium removal, as compared to chemical removal with the detergent saponin.