N(5)-(1-Iminoethyl)-L-ornithine HCl (L-NIO), is an inhibitor of NOS3 (nitric oxide synthase) in the vascular endothelium that can halt endothelium-dependent relaxation induced by acteylcholine and cause endothelium-dependent contraction in aortic rings. Mechanistic studies have noted that L-NIO inhibits Ca2+-dependent NOS3 (eNOS). The same experiment on rat aorta has shown L-NIO to display a capacity to induce a dose-dependent increase in mean systemic arterial blood pressure. In addition, research has shown L-NIO to be the most potent inhibitor of the neutrophil and J774 enzymes compared to its analogues L-NMMA, L-NAME, and L-NNA.
