Does Radioadaptive Response also Apply to the Case of Heavy-ion Irradiations in Fetal and Adult Mice? Part I. Priming Low Dose of X-irradiations Modifies Detrimental Effects from Challenging High Dose of Heavy-ion Irradiations.

In contradiction to classical paradigm, which assumes that radiation effects are directly proportional to energy deposit, numerous studies described the existence of radiation-induced adaptive response (AR), which is the phenomenon of priming low-dose irradiation-induced resistance to subsequent irradiation at higher doses. As investigations on the conditions essential for induction of these effects provide important scientific basis for radiation risk estimates and offer significant insight into the novel biological defense mechanisms regarding protection against radiation, study on AR is of great concern for both public health and academic research. In a series of study in progress, possible induction of adaptive response by high LET irradiation of accelerated heavy ions is to be tested both in vivo in young adult mice and in utero in fetal mice of C57BL/6J strain. Investigations are to verify 1) if the known X-ray-induced adaptive response could reduce any heavy-ion-induced detrimental effects such as growth retardation, death or malformation, 2) if the heavy ion irradiation at certain low doses could induce any adaptive response against the detrimental effects induced by high dose of X-irradiations, and 3) if the heavy-ion irradiation at certain low dose could induce any adaptive response against the detrimental effects induced by high dose of heavy ion irradiations. Three kinds of accelerated heavy ions are to be examined, carbon (290MeV/u) mono beams with a linear energy transfer (LET) value of about 15 keV/micro meter, silicon (490MeV/u) mono beams with a LET value of about 55 keV/micro meter, and ion (500MeV/u) mono beams with a LET value of about 200 keV/micro meter. In this report, we will present the data on the first question - if the known X-ray-induced adaptive response could reduce any heavy-ion-induced detrimental effects.