Effects of storage and reperfusion oxygen content on substrate metabolism in the isolated rat lung

Background. Lung transplantation requires a period of storage and ischemia; we examined the largely unknown effects of that period on intermediary met abolism. Methods. Two groups of isolated rat lung blocks (n = 16 each) were flushed with Euro-Collins solution and harvested. The lung blocks were immediately ventilated and either perfused for 30 minutes with an erythrocyte-based sol ution containing carbon 13 labeled substrates (group 1) or stored for 6 hou rs at 1 degrees C and then reperfused (group 2). Half of each group was rep erfused at a physiologic Po-2 the other half at high Po-2. Analysis of carb on 13 isotopomers was performed to determine substrate utilization through aerobic pathways in lung tissue. Results. Lungs from both groups oxidized all major substrates. The contribu tion of fatty acids to acetyl-coenzyme acid oxidized in the citric acid cyc le was significantly higher in group 2 than in group 1 (31.3% +/- 2.2% vers us 22.0% +/- 2.1%, p < 0.05). Perfusate Po-2 did not affect substrate prefe rence. Gas exchange was worse in stored lungs. Conclusions. After a period of hypothermic ischemia and storage, substrate preference in lung tissue exhibits a switch towards fatty acids. As fatty a cid oxidation occurring after ischemia is deleterious in other organs, stra tegies to inhibit this process in stored lungs may warrant further investig ation. (Ann Thorac Surg 2000;70:264-9) (C) 2000 by The Society of Thoracic Surgeons.