Nitric oxide synthase reduces nitrite to NO under anoxia

Abstract

Cultured bEND.3 endothelial cells show a marked increase in NO production when subjected to anoxia, even though the normal arginine pathway of NO formation is blocked due to absence of oxygen. The rate of anoxic NO production exceeds basal unstimulated NO synthesis in normoxic cells. The anoxic release of NO is mediated by endothelial nitric oxide synthase (eNOS), can be abolished by inhibitors of NOS and is accompanied by consumption of intracellular nitrite. The anoxic NO release is unaffected by the xanthine oxidase inhibitor oxypurinol. The phenomenon is attributed to anoxic reduction of intracellular nitrite by eNOS, and its magnitude and duration suggests that the nitrite reductase activity of eNOS is relevant for fast NO delivery in hypoxic vascular tissues.

Nitrite confers protection against myocardial infarction: Role of xanthine oxidoreductase, NADPH oxidase and KATP channels

“…Inhibition of the enzyme nitric oxide synthase with L-NMA did not abolish cardioprotection by nitrite, suggesting nitrite-induced cardioprotection occurs by a nitric oxide synthaseindependent mechanism. In addition it has been shown that NOS itself may function as a nitrite reductase in the absence of oxygen [37,38], but the lack of effect of L-NMA rules out this possibility in the isolated cardiac preparation used in these studies.…”

Constitutive intracellular production of iNOS and NO in human melanoma: possible role in regulation of growth and resistance to apoptosis

“…To date, there is no method that specifically measures NO in tissues, although Iron-dithiocarbamate complexes are widely used as one relative measure, and efforts to improve their specificity are anticipated [7]. Our use of the DAF method for cell lines provides a rapid and relative measure of total NO forms using standard flow cytometry instrumentation, and its application to human tumors remains distant.…”

Keeping the heart in balance: the functional interactions of myoglobin with nitrogen oxides

“…In the frog, such effects of nitrite are independent of NOS activity and disappear when the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) is added whereas in eel and icefish they depend on NOS activity but not on the addition of PTIO (Cerra et al, 2009). Whether Mb is involved in NO generation in eel and icefish hearts remains to be established, although it appears that NOS might represent a source of NO from added nitrite, as some studies have suggested (Vanin et al, 2007).…”