Oxidant generation in
anoxia-reoxygenation and
ischemia-reperfusion was compared in isolated rat lungs.
Anoxia-reoxygenation was produced by N2 ventilation followed by O2 ventilation. After
anoxia, lung
ATP content was decreased by 59%. Oxygenated
ischemia was produced by discontinuing perfusion while ventilation with O2 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 (
TBARS) increased 342%, conjugated dienes increased 285%, and
protein carbonyl content increased 46%. Pretreatment of lungs with 100 microM
allopurinol inhibited the reoxygenation-mediated increase in lung fluorescence by 75% and
TBARS by 69%. Oxygenated
ischemia resulted in an approximately eightfold increase in lung H2DCF oxidation and a fourfold increase in
TBARS, but
allopurinol had no effect. On the other hand, 100 microM
diphenyliodonium (DPI) inhibited the
ischemia-mediated increase in lung fluorescence by 69% and lung
TBARS 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.