Co-exposure to internal and external radiation alters cesium biokinetics and retention in the mouse

Exposures in post-accidental situations are complex and include both external exposure and internal contamination with several radionuclides. However, in vivo and in vitro studies generally use simplified exposures, while a recent study suggested that combined external irradiation and internal contamination may induce more severe biological effects as compared to single exposures. In an attempt to test the hypothesis of potential non-additive effects of multiple radiological exposures, we used a mouse model of combined external X rays irradiation at 1 and 5 Gy and internal contamination with injection of 20 KBq(137)Cs. Results showed a differential kinetics of(137)Cs elimination in irradiated animals as compared to sham-irradiated,(137)Cs injected animals. Moreover, changes in plasma potassium and in relative testis weight were observed 38 days after irradiation and injection in co-exposed animals as compared to(137)Cs injection alone. These results demonstrate that an external exposure combined with an internal contamination may lead to unexpected changes in biokinetics of radionuclides and biological effects as compared to single exposures.