Oxygen-dependent Protection of Radiation Lung Damage in Mice by WR 2721

SummaryThe modification of early and late radiation damage to the mouse lung by oxygen and WR 2721 has been studied by measurement of breathing rate, lethality, pleural fluid and hydroxyproline content. Protection by hypoxia and sensitization by hyperoxia of early radiation pneumonitis were demonstrated. There was a tendency for the protective effect of WR 2721 to decrease as the breathed oxygen concentration was raised above normal levels. WR 2721 protection of the late damage was higher (PF = 1·6–1·65) than was seen for early pneumonitis (PF = 1·3–1·35) when either breathing rate or lethality were used. Protection factors (PF) gained from measurements of pleural fluid at a year after treatment were similar to those for other endpoints of late damage (PF = 1·7). In contrast, the measurement of fibrosis through determinations of lung hydroxyproline at 1 year gave a somewhat lower protection factor for WR 2721. In the same experiments the degree of epilation on the dorsal thorax was scored at 6 weeks. One ...