[Endothelium-derived relaxation factor from vessels--a nitrosyl iron complex with thiol-containing ligands...

A hypothesis is presented concerning the nature of endothelium--derived relaxing factor (EDRF) of blood vessels--a compound isolated from endothelial cells under the effect of acetylcholine, bradykinin and other agents. This factor causes relaxation of the smooth muscles of these vessels. EDRF is suggested to be a nitrosyl complex of iron with low-molecular thiol-containing ligands, most probably with cysteine. Nitric oxide produced from arginine by NO-synthetase is their active component. Incorporation of NO into iron complexes stabilizes it providing transfer inside the cells and between them. Subsequent liberation of NO from these complexes results from the oxidation of thiol ligands.