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ABSTRACT
Nitric oxide (NO) is a simple ubiquitous signaling molecule and plays important roles in almost every biological system. Recent evidences suggest that NO may act as an endocrine molecule. The aim of this review is considering available literature on endocrine roles of NO and/or its metabolites, i.e. nitrite and nitrate. Existing data suggest the idea that NO is a hormone that after production in tissues, it is stabilized and transported as nitrite and/or Snitrosothiols in the blood to target cells. Iran. Biomed. J. 15 (3): 59-65, 2011
Keywords: Endocrine, Hormone, Nitric oxide (NO), Nitrate, Nitrite
HISTORY
Nitric oxide (NO) was discovered in 1772 [1]. Nitroglycerine (NG), a vasodilator acting via NO production, was synthesized in 1847 [2, 3]. The effect of NG was studied on healthy volunteers by Constantin Hering in 1849 and it was proven to cause headache [2]. Later in 1878, NG was used by William Murrell for the first time to treat angina [2]. Towards the end of 19th century, NG was established as a remedy for relief of anginal pain [2]. In 1916, Mitchell et al. [4] suggested that body tissues can also produce nitrate and Richard Bodo [5] in 1928 showed a dosedependent increase of coronary flow in response to sodium nitrite administration. In 1970s, it was shown that nitrite-containing compounds stimulate guanylate cyclase and increase cyclic guanosine monophosphate (cGMP) which causes vascular relaxation and it is presumed that cGMP activation may occur via the formation of NO [2].
In 1980, Furchgott and Zawadzki [6] showed that endothelial cells are required for acetylcholine-induced relaxation of vascular bed through the endotheliumderived relaxing factor. Thereafter in 1987, it was shown that endothelium-derived relaxing factor and NO are the same or almost the same [7-9]. In 1992, NO was proclaimed as the molecule of the year [10] and in 1999, Furchgott, Ignarro, and Murad were awarded the Nobel Prize in Physiology or Medicine for studies in the NO field [1]. Due to the proven roles played by NO physiologically and pathologically, research on NO was increased rapidly and at the end of 20th century, the rate of NO publications was approximately 6,000 papers per year [1], with currently more than 100,000 references invoking NO listed in PubMed.
NO synthesis. NO is...