[From endothelium-derived relaxing factor to L-arginine and nitrogen monoxide]

Endothelium-derived relaxing factor has been identified as nitric oxide. It was originally found to be released from endothelial cells, mediating vascular relaxation and platelet inhibitory action. Nitric oxide is formed enzymatically from L-arginine by nitric oxide synthase, and this enzyme has up to the present been demonstrated in endothelial cells, platelets, neutrophils, macrophages, neurons and smooth muscle cells. Both a constitutive and an inducible nitric oxide synthase have been identified, which may serve different physiological/pathophysiological purposes. The biological implications of nitric oxide have now been manifested, and the number of reports on its physiological role is rapidly increasing. Compounds which inhibit the formation of nitric oxide have become available, and this expanding field has created great interest amongst clinicians.