Uptake of carbon monoxide by C3H mice following X irradiation of lung only or total-body irradiation with 60Co

Carbon monoxide uptake (Vco) and ventilation rate (VR) of C3H mice were determined at 14 weeks following either X irradiation of lungs only or total-body irradiation with 60Co at different dose rates. Following localized X irradiation of lung at 97 cGy/min there was a reduction in Vco, which was inversely related to radiation dose, with a small reduction below control levels being detected at 7 Gy, the lowest dose tested. An increase in VR could be detected only at doses of 11 Gy, or more. Another group of animals received 11.5 Gy total-body irradiation at either 26.2 or 4.85 cGy/min followed by transplantation with syngeneic bone marrow. Following total-body irradiation, Vco was significantly reduced by about 37% at the higher dose rate and 23% at the lower dose rate. In contrast, a trend toward elevated VR was detected only at the higher dose rate. The results indicate that Vco is a sensitive indicator of radiation-induced lung injury and that under the experimental conditions used Vco is a more sensitive indicator of radiation-induced lung injury in C3H mice than VR