pertaining to or containing nitrogen in one of its higher valences.
nitric acid a highly caustic, fuming acid that has a characteristic choking odor and can be fatal if swallowed. It is sometimes used as a cauterizing agent in the eradication of warts; large amounts of it on the skin can cause necrosis. It is also used in the form of its potassium and sodium salts. The antidote for nitric acid poisoning is liberal application of an alkali or sodium bicarbonate.
nitric oxide 1.
NO, a naturally occurring gas that in the body is a short-lived dilator released from vascular epithelial cells in response to the binding of vasodilators to endothelial cell receptors; it causes inhibition of muscular contraction, and thus relaxation. Excesses of nitric oxide are toxic to cells of the central nervous system and also cause the drop in blood pressure seen in septic shock. Called also endothelial-
or endothelium-derived relaxing factor
2. a preparation of nitric oxide used together with ventilatory support or other agents in the treatment of respiratory failure due to persistent fetal circulation in term and near-term neonates; administered by inhalation.
ni·tric ox·ide (NO·), (nī'trik oks'īd),
A colorless free-radical gas that reacts rapidly with O2 to form other nitrogen oxides (e.g., NO2, N2O3, N2O4) and ultimately is converted to nitrite (NO2-) and nitrate (NO3-); a gaseous mediator of cell-to-cell communication and potent vasodilator, formed from l-arginine in bone, brain, endothelium, granulocytes, pancreatic beta cells, and peripheral nerves by a constitutive nitric oxide synthase, and in hepatocytes, Kupffer cells, macrophages, and smooth muscle by an inducible nitric oxide synthase (e.g., induced by endotoxin). NO· activates soluble guanylate cyclase, mediates penile erection, and may be the first known retrograde neurotransmitter.
The short-lived NO molecule is a product of various tissues and plays a role in various processes. NO elaborated by endothelium, which is identical to endothelium-derived relaxing factor (EDRF), dilates vessels by relaxing vascular smooth muscle. Nitrites used in coronary and peripheral vascular disease induce or mimic this action. The 1998 Nobel Prize in Medicine or Physiology was awarded to three U.S. pharmacologists, Robert F. Furchgott, Ferid Murad, and Louis J. Ignarro, for their independent discoveries of the role of NO in cardiovascular physiology. In the immune system, macrophages use NO as a cytotoxic agent. Deficiency or inactivation of NO may contribute to the pathogenesis of both hypertension and atherosclerosis. An excess of NO, which is a free radical, is toxic to brain cells, and NO is also responsible for the precipitate, often fatal drop in blood pressure accompanying septic shock. Free NO in the bloodstream is rapidly reduced by the iron of hemoglobin.
ni·tric ox·ide (nī'trik ok'sīd)
A colorless, free-radical gas; it reacts rapidly with O2 to form other nitrogen oxides (e.g., NO2·, N2O3, and N2O4) and ultimately is converted to nitrite (NO2-) and nitrate (NO3-). Physiologically, it is a naturally occurring vasodilator formed in endothelial cells, macrophages, neutrophils, and platelets, and a mediator of cell-to-cell communication formed in bone, brain, endothelium, granulocytes, pancreatic β-cells, and peripheral nerves.