title: Nitrite-derived nitric oxide formation following ischemia-reperfusion injury in kidney.
abstract: Nitric oxide (NO) is synthesized from l-arginine by nitric oxide synthase (NOS), and nitrite and nitrate are believed to be waste forms of NO. We previously reported an enzyme-independent pathway of NO generation from nitrite in acidic conditions. In this study, we show nitrite-derived NO formation in renal ischemia-reperfusion injury using electron paramagnetic resonance (EPR) spectroscopy. In this experiment, we utilized a stable isotope of [(15)N]nitrite as a source of nitrite to distinguish l-arginine-derived NO from [(15)N]nitrite-derived (15)NO. Intravenous infusion of a stable isotope of [(15)N]nitrite ((15)NO(2)(-)) facilitated the formation of Hb(15)NO during renal ischemia, which demonstrated that the origin of NO was nitrite. The EPR signal of Hb(15)NO in kidney appeared after 40 min of renal ischemia, and renal reperfusion decreased the Hb(15)NO level in the kidney and increased it in blood by contrast. In addition, the amount of HbNO was nitrite concentration dependent, and this formation was NOS independent. Our findings suggest that nitrite can be an alternative source of NO in ischemic kidney and that it binds with hemoglobin and then is spread by the circulation after reperfusion.
authors.affiliation: Department of Pharmacology, University of Tokushima School of Medicine, 3-18-15 Kuramoto, Tokushima 770-8503, Japan.
authors.forename: Masumi
authors.initials: M
authors.lastname: Okamoto
authors.forename: Koichiro
authors.initials: K
authors.lastname: Tsuchiya
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Kanematsu
authors.forename: Yuki
authors.initials: Y
authors.lastname: Izawa
authors.forename: Masanori
authors.initials: M
authors.lastname: Yoshizumi
authors.forename: Susumu
authors.initials: S
authors.lastname: Kagawa
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Tamaki
mesh_terms: D000818:Animals; D004578:Electron Spin Resonance Spectroscopy; D006454:Hemoglobins / Q000378:metabolism; D007668:Kidney / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000378:metabolism*
chemical_list: D006454:Hemoglobins; D009573:Nitrites; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase