ABSTRACT
BACKGROUND: Cell energy during ischemia/reperfusion depends on mechanisms including adenosine diphosphate degradation, oxygen species and cytokine liberation, neutrophil infiltration, and endothelial dysfunction. Preconditioning-a brief ischemic episode that confers a state of protection against subsequent ischemia-reperfusion injury-involves NO and adenosine production, reduction in oxygen species liberation, and preservation of microcirculation. During hypoxia, constitutive NO production assures adequate oxygen delivery and reduced energy loss. The aim was to determine the role of ischemic preconditioning in the stimulation of constitutive endothelial nitric oxide (NO) production and its effect on energy charge, radical oxygen species generation, cytokine liberation, and neutrophil infiltration during reperfusion. MATERIALS AND METHODS: Rats were assigned to one of four groups depending on the preconditioning protocol: hepatic ischemia/reperfusion, or hepatic ischemia/reperfusion and ischemic preconditioning, for 5, 10, or 20 min. A portosystemic shunt was established between the portal and left jugular veins during ischemia. RESULTS: Preconditioning produced rises in plasma nitrites, but no rise in inducible nitric oxide synthase gene expression. A 5 or 10 min preconditioning period allowed for higher energy charge, bile production, and glutathione levels, with less lipoperoxide, alanine aminotransferase, tumor necrosis factor-α, and interleukin-1 production and neutrophil infiltration, compared with 20 min or control. Survival was 80% in the G10 group, 70 in G5, 10 in GC, and 0% in the G20 group. CONCLUSIONS: Ten-min liver preconditioning improves survival and prevents energy loss during hepatic ischemia/reperfusion by stimulating constitutive NO production, maintaining glutathione concentrations and reducing oxygen species and proinflammatory cytokine generation as well as neutrophil infiltration.
