University of Wisconsin and modified Euro-Collins solutions for pulmonary preservation were compared in a rat orthotopic left lung isotransplant model. Heart-lung blocks of donor rats were flushed with and preserved in one of the preservation solutions at 0 degrees C. After 6 or 12 hours of cold ischemia, the left lungs were transplanted into recipient rats and reperfused for 1 hour. Pulmonary function was assessed by measuring oxygen and carbon dioxide tensions in arterial blood after removal of the right lung. Lipid peroxide concentrations were measured as thiobarbiturate acid-reactive substances. The ratios of wet to dry weight of grafts after ischemia and after reperfusion were calculated. Histologic changes of ischemia-reperfusion injury of the lung tissue were evaluated using a graded scale. Oxygen tension after 6 hours of preservation followed by reperfusion was significantly higher with University of Wisconsin solution (308.8 +/- 81.1 mm Hg) than with Euro-Collins solution (50.8 +/- 17.8 mm Hg; p less than 0.001). Carbon dioxide tension in the University of Wisconsin solution group was also significantly lower than in the Euro-Collins solution group (28.2 +/- 2.3 versus 46.0 +/- 4.5 mm Hg; p less than 0.05). Lipid peroxide concentration after 6 hours' preservation in University of Wisconsin solution was significantly lower (0.88 +/- 0.07 mumol/g) than that in Euro-Collins solution (1.26 +/- 0.12 mumol/g; p less than 0.05). After 12 hours of preservation only lipid peroxide concentration with University of Wisconsin solution was significantly lower (1.30 +/- 0.09 mumol/g) than with Euro-Collins solution (1.71 +/- 0.15 mumol/g; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)