Endothelial cells in culture produce a vasoconstrictor substance

We report that cultured vascular endothelial cells release into the culture medium a vasoconstrictor peptide, a substance we call an endotheliumderived constricting factor (EDCF). Conditioned medium from cultured bovine aortic and pulmonary artery endothelial cells caused sustained, dose‐dependent isometric constriction of vascular rings isolated from bovine coronary and pulmonary arteries and rat and guinea pig pulmonary arteries and aortas. The medium also caused vasoconstriction when infused into isolated, perfused rabbit hearts and rat kidneys. Conditioned medium from bovine aortic intimal explants also contained constrictor activity, whereas medium from denuded intimal explants, cultured microvascular endothelial cells, vascular smooth muscle cells, or lung fibroblasts did not. Constrictor activity increased progressively in the culture medium over 2–12 h of incubation. Thrombin stimulated the release of constrictor activity; hypoxia, anoxia and meclofenamate had no effect and the calcium ionophore A23187 inhibited EDCF release. The EDCF caused a characteristic slow‐onset and sustained constriction of the vascular rings that relaxed slowly over 60–90 min following removal. The constriction was not affected by inhibitors of arachidonic acid metabolism or by antagonists of serotonergic, histaminergic, aloha‐adrenergic, opioid, leukotriene, angiotensin II, or substance P receptors; constriction was reversed partly by verapamil and acetylcholine and completely by nitroprusside and isoproterenol. EDCF was heat stable, not extractable into organic solvents, and completely destroyed by trypsin and neutral protease. Cycloheximide blocked the production of EDCF. These properties and the results of polyacrylamide gel filtration experiments suggested that EDCF was a peptide with a molecular weight of 3,000 daltons. These findings show that endothelial cells in culture produce a vasoconstrictor substance and support the idea that endothelial cell products play a role in mediating vascular tone.