INHIBITION OF URETHAN LUNG TUMOR INDUCTION IN MICE BY TOTAL-BODY X IRRADIATION

Groups of young adult (C57L x A)F/sub 1/ mice received a single intraperitoneal injection of urethan prior to or after a single whole-body lethal dose of x rays (880 rad) followed by transfusion of normal syngeneic bone marrow to protect against radiation death. This dose of urethan produced multiple tumors in 100% of nonirradiated animals at 24 weeks postinjection. In the irradiated animals there was marked suppression of lung tumor formation, both in number of animals with tumors, and in numbers of tumors per tumor-bearing animal. This suppression was present whether urethan treatment preceded or followed radiation. The results imply that urethan lung carcinogenesis may be interfered with by a direct inhibitory effect of the radiation on cells already altered by urethan, or through latent radiation inhibition of pulmonary alveolar proliferative capacity. (auth)