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URETHAN-INDUCED LUNG TUMORS IN MICE: X-RADIATION DOSE DEPENDENT INHIBITION,
NAVAL RADIOLOGICAL DEFENSE LAB SAN FRANCISCO CALIF
Adult male LAF sub 1 mice received single wholebody X ray exposures of 100, 300, 500, or 700 rads, followed one day later by single injections of urethan 1 mgg. The mice were sacrificed 25 weeks later, and the lungs examined grossly and microscopically for tumors. All of the mice in group receiving 100 rad plus urethan exhibited lung tumors alveologenic carcinomas, with a mean of 3.1 tumors per mouse. This lung tumor incidence was identical with that occurring in the mise which received urethan only. However, a definite reduction in lung tumor incidence and number of tumors per mouse was observed at the 500 rad dose 66 incidence and 1.8 tumors per mouse, respectively and at 700 rad 59 incidence and 1.3 tumors per mouse. Thus, the X radiation suppression of urethan-induced lung tumors in mice is dose-dependent in the range of 500 rad to 900 rad. The data suggest that this tumor suppression is correlated with a direct radiation inhibition of alveolar cell proliferation. Author