Anoxia-reoxygenation versus ischemia in isolated rat lungs

Oxidant generation in anoxia-reoxygenation and ischemia-reperfusion was compared in isolated rat lungs. Anoxia-reoxygenation was produced by Nz ventilation followed by O-2 ventilation. After anoxia, lung ATP content was decreased by 59%. Oxygenated ischemia was produced by discontinuing perfusion while ventilation with O-2 was maintained. With anoxia-reoxygenation, oxidant generation, evaluated by oxidation of dichlorodihydrofluorescein (H2DCF) to fluorescent dichlorofluorescein, increased 3.6-fold, lung thiobarbituric acid reactive substances (TEARS) increased 342%, conjugated dienes increased 285%, and protein carbonyl content increased 46%. Pretreatment of lungs with 100 mu M allopurinol inhibited the reoxygenation-mediated increase in lung fluorescence by 75% and TEARS by 69%. Oxygenated ischemia resulted in an approximately eightfold increase in lung H2DCF oxidation and a fourfold increase in TEARS, but allopurinol had no effect. On the other hand, 100 mu M diphenyliodonium (DPI) inhibited the ischemia-mediated increase in lung fluorescence by 69% and lung TEARS by 70%, but it had no effect on the increase with anoxia-reoxygenation. Therefore, both ischemia-reperfusion and anoxia-reoxygenation result in oxidant generation by the lung, but a comparison of results with a xanthine oxidase inhibitor (allopurinol) and a flavoprotein inhibitor (DPI) indicate that the pathways for oxidant generation are distinctly different.