LUNG REPERFUSION INJURY AFTER CHRONIC OR ACUTE UNILATERAL PULMONARY-ARTERY OCCLUSION

Because the lungs receive their blood supply from both the pulmonary a nd bronchial systems, chronic pulmonary artery obstruction does not ne cessarily result in severe ischemia. Ischemia-reperfusion (IR) lung in jury may therefore be attenuated after long-term pulmonary artery obst ruction. To test this hypothesis, isolated left lungs of pigs were rep erfused two days (acute IR group) or 5 wk (chronic IR group) after lef t pulmonary artery ligation and compared to those of sham-operated ani mals. The severity of IR-lung injury after 60 min ex vivo reperfusion of the left lung was assessed based on lung histology and measurements of filtration coefficient (K-fc), pulmonary arterial resistance (Rpa) , and lung myeloperoxidase (MPO) activity. Marked bronchial circulatio n hypertrophy was seen in the chronic IR group. Hemorrhagic alveolar e dema was found in all acute IR lungs but not in sham or chronic IR lun gs. Compared with the sham-operated controls, K-fc and Rpa increased t wofold and threefold, and MPO 1.5-fold and twofold in the chronic and acute IR groups, respectively. In conclusion, IR-induced lung injury w as markedly reduced when it occurred 5 wk after pulmonary artery ligat ion, probably because the systemic blood supply to the lung had time t o develop, limiting ischemia.