A free radical gas produced endogenously by a variety of mammalian cells. It is synthesized from arginine by a complex reaction, catalyzed by nitric oxide synthase. Nitric oxide is endothelium-derived relaxing factor. It is released by the vascular endothelium and mediates the relaxation induced by some vasodilators such as acetylcholine and bradykinin. It also inhibits platelet aggregation, induces disaggregation of aggregated platelets, and inhibits platelet adhesion to the vascular endothelium. Nitric oxide activates cytosolic guanylate cyclase and thus elevates intracellular levels of cyclic GMP.
A molecule, produced in the body, which acts as a signalling molecule, oxidant utilized against pathogens by the immune system, and (destructive) free radical. As a “messenger molecule,” nitric oxide is utilized by the body for control of blood pressure, immune system regulation, neural signalling, etc.
A substance released from the cells lining the arteries and arterioles, which causes relaxation of smooth muscle and dilation of the vessels.
A naturally occurring chemical that performs a wide range of biological roles. It is involved in the laying down of memories in the brain; in killing viruses, bacteria and cancer cells; and in helping to control blood pressure. No, comprising a nitrogen atom attached to an oxygen one, is one of the smallest of biologically active compounds as well as having such diverse functions. The chemical is a muscle relaxant and is important in maintaining the heart and circulation in good condition. No is also the toxic agent released by macrophages to kill invading germs and spreading cancer cells. It acts as an essential neurotransmitter and protects nerve cells against stress. Researchers are studying how it might be used to treat diseases, for example by using it as an inhaled gas in certain respiratory conditions.
A soluble gas that is normally produced in the human body and is present in expired air at a concentration of about 10 parts per billion. Produced by endothelial cells, neurons in the brain, and macrophages during inflammation, it is a potent vasodilator. Nitric oxide has many other roles: it inhibits the adhesion, activation, and aggregation of platelets and the inflammatory process induced by mast cells; controls chemotaxis of lymphocytes; regulates smooth muscle cell proliferation, penile erection, and other sexual functions; participates in programmed cell death; and interacts with oxygen radicals to form metabolites that destroy pathogens. When NO is given as part of a mixture of inhaled gas, it decreases recruitment of lymphocytes. In the acute respiratory distress syndrome, NO improves oxygenation but does not impact patient survival. Previously, NO was called endothelium-derived relaxing factor.
This gas is generated both externally as a pollutant (like in automobile exhaust emissions) and internally within the body, functioning as a molecule that acts as a messenger between cells.
Nitric oxide induces the expansion of blood vessels, influencing the circulation of oxygen-rich blood and managing blood pressure. Excessive production of nitric oxide is linked to different conditions such as toxic shock syndrome and rheumatoid arthritis. Conversely, insufficient production can lead to issues like impotence and angina. Regulating nitric oxide holds significance in numerous medicinal interventions.