Nitric oxide availability

C.M. Tolias, J.C. McNeil, J. Kazlauskate, and E.W. Hillhouse, Superoxide generation from constitutive nitric oxide synthase in astrocytes in vitro regulates extracellular nitric oxide availability. Free Radical Biol. Med. 26, 99-106 (1999). 

A study has been undertaken to clarify whether glucocorticoid excess affects endothelium-dependent vascular relaxation in glucocorticoid treated patients and whether dexamethasone alters the production of hydrogen peroxide and the formation of peroxynitrite, a reactive molecule between nitric oxide and superoxide, in cultured human umbilical endothelial cells (7). Glucocorticoid excess impaired endothelium-dependent vascular relaxation in vivo and enhanced the production of reactive oxygen species to cause increased production of peroxynitrite in vitro. Glucocorticoid-induced reduction in nitric oxide availability may cause vascular endothelial dysfunction, leading to hypertension and atherosclerosis. 

Hwang J, Wang J, Morazzoni P, Hodis HN, Sevanian A. 2003. The phytoestrogen equol increases nitric oxide availability by inhibiting superoxide production An antioxidant mechanism for cell-mediated LDL modification. Free Radic Biol Med 34 1271-1282. 

It is available commercially from several routes including as a product from the manufacture of sodium nitrate from sodium chloride and nitric acid, and from a process involving the passage of ammonia and air over heated platinum and treating the nitric oxide so formed with oxygen. 

A sophisticated quantitative analysis of experimental data was performed by Voltz et al. (96). Their experiment was performed over commercially available platinum catalysts on pellets and monoliths, with temperatures and gaseous compositions simulating exhaust gases. They found that carbon monoxide, propylene, and nitric oxide all exhibit strong poisoning effects on all kinetic rates. Their data can be fitted by equations of the form ... 

It is possible to replace one isocyanide by triphenylphosphine, or to replace two isocyanides with diphos, giving phosphine analogues of these complexes. These species are not available from analogous reactions of phosphine-palladium(O) and (II) complexes. Reactions with active alkyl halides proceeds with oxidation nitric oxide also oxidizes these complexes. [Eqs. (31, 32)]. 

Dipyridamole exerts its effect by inhibition of platelet phosphodiesterase E5, increasing cyclic guanosine monophosphate and cyclic adenosine monophosphate (cAMP). By inhibiting its uptake and metabolism by erythrocytes, dipyridamole also increases the availability of adenosine within blood vessels, promoting inhibition of platelet aggregation and local vasodilatation. " Dipyridamole may also inhibit cAMP phosphodiesterase in platelets, which further increases cAMP levels and may enhance endothelial nitric oxide production, contributing to its antithrombotic effect. Existing trials of dipyridamole in stroke have focused on secondary prevention and will be discussed briefly. 

The vascular endothelium produces a number of substances that are released basally into the blood vessel wall to alter vascular smooth muscle tone. One such substance is endothelin (ET-1). Endothelin exerts its effects throughout the body, causing vasoconstriction as well as positive inotropic and chronotropic effects on the heart. The resulting increases in TPR and CO contribute to an increase in MAP. Synthesis of endothelin appears to be enhanced by many stimuli, including Ag II, vasopressin, and the mechanical stress of blood flow on the endothelium. Synthesis is inhibited by vasodilator substances such as prostacyclin, nitric oxide, and atrial natriuretic peptide. There is evidence that endothelin is involved with the pathophysiology of many cardiovascular diseases, including hypertension, heart failure, and myocardial infarction. Endothelin receptor antagonists are currently available for research use only. 

A convenient preparative method for conjugated nitroalkenes has been developed based on the reaction of nitrogen oxides. Nitric oxide (NO) is commercially available and used in the industry for the mass production of nitric acid. Nitric oxide is currently one of the most studied molecules in the fields of biochemistry, medicine, and environmental science.47 Thus, the reaction of NO with alkenes under aerobic conditions is of a renewed importance.48... 

Because of its relevance to the chemistry of air at elevated temperatures the homogeneous decomposition of nitric oxide has received considerable attention from gas kineticists. References to early studies are given in the more recent work discussed below. The mechanisms for the decomposition and for the reverse reaction, the formation of NO from air, are well established and good quantitative data (Table 12) are available for the rate coefficients of the elementary steps. 

Some oxidation of combined nitrogen to nitric oxide may take place when measurements are made low in a range, so that an excess of oxygen is available for combustion. 

Nitric oxide coordinated to iron modifies, in a striking manner, the properties and reactivity of free NO (Sec. 6.2). Probably the most famous such coordinated entity is the nitroprusside ion, Fe(CN)5NO . An incisive review of its reactions particularly related to its hypertensive action (it reduces blood pressure of severely hypertensive patients) is available. Nitroprusside ion reacts with a variety of bases... 

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