Endothelial NOS, or endothelial nitric oxide synthase, is an enzyme found in the endothelial cells that line blood vessels. It plays a crucial role in producing nitric oxide, a signaling molecule that helps regulate blood flow and maintain vascular health. By promoting the relaxation of blood vessels, endothelial NOS contributes to the overall cardiovascular function. The activity of endothelial NOS is influenced by various factors, including shear stress from blood flow and the presence of certain hormones. Proper functioning of this enzyme is essential for preventing conditions like hypertension and atherosclerosis, which can lead to serious cardiovascular diseases.