WR 2721 modification of type II cell and endothelial cell function in mouse lung after single doses of radiation.

The ability of WR 2721 to protect endothelial cells and Type II cells in mouse lung after single doses of X rays was studied using specific assays of cell function to assess damage. The whole thorax of mice was exposed to a range of single doses of X rays either alone or 30 minutes after an i.p. injection of 400 mg/kg of WR 2721. Endothelial cell function was assayed by angiotensin converting enzyme (ACE) and Type II cell function by phosphatidylcholine and total protein present in lavage fluid 28 days after radiation. Similar protection factors (PFs) were found for the functional activity of both cell types, 1.2 and 1.24 for ACE and phosphatidylcholine respectively. These values were somewhat less than the PF of 1.37 for lethality from pneumonitis 7 to 9 months after irradiation for this mouse strain. The lack of a clear difference between the PFs for the functional activity of these two cell types suggests that neither the endothelial cell nor the Type II cell can be accepted or excluded as the target cell for radiation pneumonitis in lung.