Effects of sodium nitrite on ischemia-reperfusion injury in the rat kidney
Nephrology Research and Training Center, Department of Medicine, University of Alabama at Birmingham, 35294, USA.American journal of physiology. Renal physiology (Impact Factor: 3.25). 05/2006; 290(4):F779-86. DOI: 10.1152/ajprenal.00334.2005
Reactive oxygen and nitrogen species play a key role in the pathophysiology of renal ischemia-reperfusion (I/R) injury. Recent studies have shown that nitrite (NO(2)(-)) serves as an endogenous source of nitric oxide (NO), particularly in the presence of hypoxia and acidosis. Nanomolar concentrations of NO(2)(-) reduce injury following I/R in the liver and heart in vivo. The purpose of this study was to evaluate the role of NO(2)(-) in renal I/R injury. Male Sprague-Dawley rats underwent a unilateral nephrectomy followed by 45 min of ischemia of the contralateral kidney or sham surgery under isoflurane anesthesia. Animals received normal saline, sodium NO(2)(-), or sodium nitrate (NO(3)(-); 1.2 nmol/g body wt ip) at 22.5 min after induction of ischemia or 15 min before ischemia. A separate set of animals received saline, NO(2)(-), or NO(3)(-) (0.12, 1.2, or 12 nmol/g body wt iv) 45 min before ischemia. Serum creatinine and blood urea nitrogen were increased following I/R injury but were not significantly different among treatment groups at 24 and 48 h after acute renal injury. Interestingly, NO(3)(-) administration appeared to worsen renal injury. Histological scoring for loss of brush border, tubular necrosis, and red blood cell extravasation showed no significant differences among the treatment groups. The results indicate that, contrary to the protective effects of NO(2)(-) in I/R injury of the liver and heart, NO(2)(-) does not provide protection in renal I/R injury and suggest a unique metabolism of NO(2)(-) in the kidney.
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- "Reactive oxygen species (ROS) and nitric oxide (NO) play an important role in mediating cell damage during IR injury. Inflammation contributes substantially to the pathogenesis of IR with a central role for particular cells, adhesion molecules and cytokines. "
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- "Thus, erythrocytes are assumed to export NO molecules, particularly at the precapillary arterioles where the P 50 of hemoglobin can most likely be achieved, provided NO bioactivity can be transported through protected mechanisms. Physiological experiments from a number of laboratories have shown that the addition of nitrite can cause downstream vasodilation and nitrite does indeed act as a vasodilator under hypoxic conditions    . In addition to the nitrite reduction by hemoglobin, certain proteins in the extracellular region, such as xanthine oxidoreductase and mitochondrial proteins, can reduce nitrite to NO to regulate tissue oxygenation and other physiological functions   . "
ABSTRACT: Nitric oxide (NO) is a potent regulator of vascular tone and hemorheology. The signaling function of NO was largely unappreciated until approximately 30 years ago, when the endothelium-derived relaxing factor (EDRF) was identified as NO. Since then, NO from the endothelium has been considered the major source of NO in the vasculature and a contributor to the paracrine regulation of blood hemodynamics. Because NO is highly reactive, and its half-life in vivo is only a few seconds (even less in the bloodstream), any NO bioactivity derived from the intraluminal region has traditionally been considered insignificant. However, the availability and significance of NO signaling molecules derived from intraluminal sources, particularly erythrocytes, have gained attention in recent years. Multiple potential sources of NO bioactivity have been identified in the blood, but unresolved questions remain concerning these proposed sources and how the NO released via these pathways actually interacts with intravascular and extravascular targets. Here we review the hypotheses that have been put forward concerning blood-borne NO and its contribution to hemorheological properties and the regulation of vascular tone, with an emphasis on the quantitative aspects of these processes.
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- "Ischemia leads to hypoxia due to a decrease or stop in blood supply and thus oxygen tension and tissue pH will decrease providing more optimal conditions for nitrite reduction back to NO either through acidification/protonation or through enzymatic reduction. While nitrite has been shown to be protective in ischemia/ reperfusion (I/R) injury in the heart and liver, it was recently revealed that nitrite provides no protection in renal I/R injury . This clearly demonstrates tissue-specific metabolism of nitrite. "
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