Does radioadaptive response also apply to the case of heavy-ion irradiations in fetal and adult mice?

Possible induction of adaptive response (AR) by the high linear energy transfer (LET) accelerated heavy ion irradiations (HI) is being attempted both in young adult female mice and in fetal mice of C57BL/6J Jms strain, using growth delay, hematopoietic damage and reduced survival in vivo, prenatal growth delay, malformation and death in utero as endpoints. Investigations are to verify if priming dose from low LET X-irradiation could induce an AR against the detrimental effects from the high challenging dose of HI, if priming dose from HI could induce an AR against the high challenging dose from low LET X-irradiations, and if an AR could be induced when both priming and challenging doses are from HI. Four kinds of HI are being examined: carbon, neon, silicon and iron, with the LET values of about 15, 30, 55, and 200 keV/micrometer, respectively. Results show that the priming low dose X-irradiations could induce AR against high LET heavy-ion challenging irradiations from carbon and silicon beams in vivo and in utero, but not iron ions in vivo; the priming low dose carbon-ion irradiations could induce AR against the high challenging irradiations in vivo from X-rays or carbon ions, but not silicon and iron ions; priming dose from carbon, silicon or iron ions could not induce any AR against challenging dose from X-rays in utero. It seems that AR induction at whole body level is radiation quality-related event. Further investigations are needed to answer if this event is of LET- or/and nuclide-dependency. (author)