Release of EDRF from human umbilical vessels.

The principal objective of this study was to determine the capability of human umbilical vessels of normal parturients to produce and to release the endothelial-derived relaxing factor. A bolus of bradykinin injected in the perfusion system of human umbilical vessels induces a release of a relaxant factor, detectable by bioassay, that is pharmacologically similar to the endothelial-derived relaxing factor. Human umbilical cords were collected from normal parturients. We demonstrated that human umbilical vessels were capable to release endothelial-derived relaxing factor. In fact, in umbilical vessels collected from normal parturients, bradykinin at a dose of 20 pmol produces a release of endothelial-derived relaxing factor equivalent to a relaxation induced by 59.9 +/- 11.0 and 30.8 +/- 11.4 pmol of glyceryl trinitrate for the artery and vein, respectively. Our results indicate that this factor is produced in human cord vessels. An alteration of endothelial cell numbers or an alteration of the enzymatic pathway could be responsable of hypertension induced by pregnancy.