nitric oxide
/add to existingnitric oxide (nitrogen monoxide) A gaseous mediator in mammals and other vertebrates, especially in the cardiovascular and nervous systems. It is produced in tissues from molecular oxygen and the amino acid arginine by the enzyme nitric oxide synthase and diffuses to neighbouring cells, where it stimulates formation of the intracellular messenger cyclic GMP. The effects of nitric oxide include relaxation of smooth muscle and dilation of blood vessels. It also inhibits platelet aggregation and adhesion, may act as a neurotransmitter in some tissues, and may influence neuronal development. Certain cells of the immune system also produce nitric oxide, which is converted to the cytotoxic peroxynitrite anion (–O–O–N=O). This has nonspecific activity against tumour cells and pathogens, including protozoan and metazoan parasites.
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nitric oxide
