Wang, B., Ohyama, H., Haginoya, K., Odaka, T., Itsukaichi, H., Yukawa, O., Yamada, T. and Hayata, I. Adaptive Response in Embryogenesis. III. Relationship to Radiation-Induced Apoptosis and Trp53 Gene Status.

We reported previously that a radiation-induced adaptive response existed in the late period of embryogenesis, and that radiation-induced apoptosis in the predigital regions was responsible for digital defects in embryonic ICR mice. To investigate the possible involvement of the Trp53 gene and radiation-induced apoptosis in radiation-induced adaptive responses in embryogenesis, the present study was conducted using Trp53 wild-type (Trp53 ^/ ) and Trp53 heterozygous (Trp53 ^/–) embryonic mice of the C57BL/6 strain. The existence of a radioadaptive response in the Trp53 ^/ embryonic mice was demonstrated by irradiating the embryos with 5 or 30 cGy on embryonic day 11 prior to a challenging irradiation at 3 Gy on embryonic day 12. The two conditioning doses at 5 and 30 cGy significantly suppressed the induction of apoptosis by the challenging dose in the predigital regions of limb buds in the Trp53 ^/ embryonic mice, while no such effect was found in the Trp53 ^/– embryonic mice. These findings indicate that induction of a radioadaptive response in embryogenesis is related to Trp53 gene status and the occurrence of radiation-induced apoptosis.