Limited availability of donor organs is a major factor restricting the clinical application of lung transplantation. Improvements in preservation techniques are essential for prolonging storage time and improving lung function following transplantation. The present inves-tigation used primary cultures of adult rat alveolar type II cells as a model for evaluating lung-preservation solutions. Type II cells were plated onto tissue-culture plastic at a density 5×l05 cells/cm2 and maintained in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum (DIO) for 40 hr. Cells were then exposed to Euro-Collins solution or a low-potassium- dextran solution (LPD). At designated time points, measurements of lactate-dehydrogenase (LDH) release, protein content, and incorporation of3H-thymidine into cellular DNA were made. During 12 hr of “storage” at 37°C, cells maintained in LPD released less LDH (14.3± 1.2% of cellular total, mean ±SEM, n=5) than their counterparts stored in EC (20.6±1.6%, P<0.05). During the 36 hr following a 6-hr exposure to preservative solutions, LPD-treated cells incorporated more thymidine per mg of protein (2566±419.8 cpm/μg protein, mean ±SEM, n=6) compared with cells maintained continuously in DIO (1431±351, P<0.05). By contrast, cells exposed to EC incorporated less thymidine (82.2± 62.8 cpm/μg protein) than either cells maintained in LPD or D10 (P<0.01 for each comparison). These results suggest that LPD solution is less cytotoxic than EC and that LPD enables higher levels of metabolic activity in recovering epithelial cells. In vitro cultures of type II epithelial cells are a useful model system for the study of lung preservation and posttransplantation lung injury.