Nitric oxide (NO) is formed from L-arginine by means of endothelial NO-synthase (eNOS). NO participates in regulation of physiologically important functions of the cardiovascular system (it regulates the contractive reduction of heart, cell proliferation, vascular tension, and blood pressure) and the immune and nervous systems. NO synthesis varies in response to factors related to inflammation, hypoxia, lipids, etc. The rate of transcription of the eNOS gene depends on the polymorphic alleles of the eNOS gene and the post-transcription mechanisms that maintain mRNA stability. All of these factors influence the development of cardiovascular events.