Functional and biochemical assessment of postpreservation lung viability in a rat model

We examined the relationship between DNA synthesis and postpreservation lung hemodynamics and gas exchange. Adult male Wistar rats (n = 168) were randomly allocated into seven groups (n = 24) according to the pulmonary vascular flush used [EuroCollins (EC), saline, or no flush] and to the temperature of flush and storage (4, 21, or 37°C). In each group, lungs were stored for four different time periods (0-24 h). After storage, incorporation of [³H]-thymidine into DNA was measured in the right lung, and in 72 rats the left lung was reperfused for 1 h with venous blood in an ex vivo paracorporeal rat lung system. Autoradiography of EC lungs revealed that alveolar macrophages and epithelial cells were the two major cell types synthesizing DNA during ischemia. Gas exchange after preservation with EC was universally poor. In unflushed and saline-flushed lungs, a critical threshold for viability was detected beyond which DNA synthesis and lung effluent PO₂ decreased more rapidly at higher storage temperatures. A positive correlation was found between the final lung effluent PO₂ and [³H]thymidine uptake (R² = 0.62; P < 0.0001). In this model, deoxyribonucleic acid synthesis was a good index of postpreservation hemodynamics and gas exchange function.