Nitrite-derived nitric oxide formation and its pathophysiological effects following ischemia-reperfusion injury in kidney

一氧化氮(NO)具有多种生理功能，一氧化氮合酶(NOS)通过催化氧、四氢生物蝶呤和NADPH依赖的氧化L-精氨酸来产生NO，亚硝酸盐和硝酸盐被认为是NO的一种废物形式。我们假设，口服亚硝酸盐被分解成NO，而这个NO分布到血液中，并在体内具有生理作用。在这项研究中，我们用电子顺磁共振(EPR)波谱测定了全血中作为循环NO指标的血红蛋白(Hb)-NO，显示了肾缺血再灌注损伤中亚硝酸盐来源的NO的形成。1.静脉注射亚硝酸钠促进肾缺血时HbNO的生成，表明NO的来源是亚硝酸盐。2.肾缺血40分钟后肾组织中HbNO的EPR信号出现，肾再灌流使肾组织中HbNO水平降低，而血液中HbNO水平升高。3.HbNO的含量呈浓度依赖性，这种形成不依赖一氧化氮合酶。4.L治疗3周后，血压明显升高，联合应用亚硝酸钠(1000 mg/L)可减轻L名诱发的高血压(L名；170+/11 mm Hg vs-NAME+亚硝酸盐；141+/-16毫米汞)。此外，亚硝酸盐与L合用可减轻L引起的肾脏病理改变。这些结果表明，口服亚硝酸盐增加循环NO，对肾脏缺血再灌注损伤可能具有重要的生理保护作用。

Nitric oxide (NO) has many physiological functions, and nitric oxide synthase (NOS) makes NO by catalyzing the oxygen-, tetrahydrobiopterin-, and NADPH-dependent oxidation of L-arginine, and nitrite and nitrate are recognized as a waste forms of NO. We hypothesized that oral nitrite is decomposed to NO, and this NO is distributes to the blood and have a physiological role in vivo. In this study, we measured hemoglobin(Hb)-NO as an index of circulating NO in whole blood using electron paramagnetic resonance (EPR) spectroscopy and showed nitrite-derived NO formation in renal ischemia-reperfusion injury.<Results>1.Intravenous infusion of sodium nitrite facilitated the formation of HbNO during renal ischemia, which demonstrated that the origin of NO was nitrite.2.The EPR signal of HbNO in kidney appeared after 40 min of renal ischemia, and renal reperfusion decreased the HbNO level in the kidney and increased it in blood by contrast.3.The amount of HbNO was nitrite concentration dependent, and this formation was NOS independent.4.Three weeks of of L-NAME treatment resulted in a marked rise in systolic blood pressure and co-administration of sodium nitrite (1000mg/L) lessened the L-NAME-induced hypertension (L-NAME ; 170+/-11mmHg vs L-NAME+nitrite;141+/-16mmHg). In addition, co-administration of nitrite with L-NAME attenuated L-NAME-induced renal histrogical changes.These results suggest that oral nitrite increases circulating NO and may have an important physiological role in protecting following ischemia-reperfusion injury in kidney.