Similarity between the vasorelaxing activity of dinitrosyl iron cysteine complexes and endothelium-derived relaxing factor.

Dinitrosyl iron complexes with cysteine (DNIC) induced a concentration-dependent relaxation of pre-contracted (norepinephrine, 10(-7) M) de-endothelialized ring segments of rat aorta. The vasodilator response was more similar to acetylcholine (ACh)-induced relaxation in intact aortic rings than to nitric oxide (NO)-induced relaxation. The time course of tone recovery after maximal concentrations (10(-5) M) of DNIC was similar to the time course of tone recovery after endothelium-dependent relaxation induced by ACh, whereas the restoration of tone after NO was much faster. Vessel tone was restored by oxyhemoglobin (10(-5) M) in all cases. The results suggest that DNIC with cysteine may function as endothelium-derived relaxing factor in the vessels.