The effect of breathing 100% oxygen on lung response to radiation in mice

The response of the lung after single doses of radiation was measured in mice breathing air, or 100% oxygen, or in air-breathing mice given the hypoxic cell sensitizer misonidazole 30 min before irradiation. There was a clear enhancement of only the pneumonitis response in the mice breathing oxygen when breathing rate or lethality was used to assess injury. Less enhancement of the late fibrotic reaction was observed in these animals. No enhancement of either phase of lung response was observed in the misonidazole-treated mice. Dose reduction factors (DRF) were estimated from these data and used to calculate oxygen concentration in the lung, giving values ranging between 187 and 250 micron oxygen.