Aim: To investigate the contribution of prostanoids to the oxygen-dependent regulation of human umbilical vein vascular tone.
Methods: Intracellular membrane potential and isometric tension of intact and endothelium-denuded human umbilical vein strips with and without cyclooxygenase inhibition by indomethacin (10(-5) M) were recorded simultaneously during variation of the local pO2.
Results: Decreasing pO2 from 39 to 5 mm Hg resulted in hyperpolarization and decrease in isometric tension of intact preparations. These effects did not occur in indomethacin treated preparations. Endothelium-denuded preparations revealed pronounced depolarization and increase in tension with decreasing pO2. Indomethacin treatment abolished these effects. With increasing pO2 from 39 to 104 mm Hg intact preparations depolarized and isometric tension remained stable. Removal of the endothelium or treatment with indomethacin reversed these effects.
Conclusions: This study confirms that the human umbilical vein actively regulates its vascular tone which is under the control of PO2. Vasodilating endothelial prostanoids contribute to the hypoxic vasodilatation and thereby counteract the vasoconstricting actions of prostanoids released from vascular smooth muscle cells. Our results indicate that vasoconstricting prostanoids are released from the endothelium of the human umbilical vein at hyperoxia.