Lack of adaptive response of gamma radiation for protection against neutron-induced teratogenesis

BACKGROUND: Although there are some reports on neutron teratology, there is little information on the adaptive response of gamma radiation for protection against neutron‐induced teratogenesis. This study examined whether or not a low dose of gamma radiation can induce an adaptive response in mouse fetuses exposed to a subsequent dose of neutrons in vivo. METHODS: Pregnant ICR mice were exposed to a priming dose of 0.3 Gy (0.9 Gy/min) of gamma rays on day 10.5 of gestation and challenged with 0.8 Gy (0.94 Gy/minute) of neutrons 24 hlater. The mice were sacrificed on day 18.5 of gestation. The fetuses were examined for mortality, growth retardation, and other morphologic abnormalities. RESULTS: The tail length in the 0.3 Gy of gamma rays + 0.8 Gy of neutrons group was significantly shorter than in the 0.8 Gy of neutrons group. Although there was no significant difference compared with the 0.8 Gy of neutrons group, the number of live fetuses in the 0.3 Gy of gamma rays +0.8 Gy of neutrons group was lower. There was no evidence of primed exposure‐related reductions in the malformed fetuses. Although there was no significant difference compared with the unprimed group, the number of malformed offspring in the primed group was higher. Furthermore, the incidence of kinked tail and adactyly was significantly higher in the primed mice than in the unprimed mice. CONCLUSIONS: Overall, this study shows that exposure to 0.3 Gy of gamma rays failed to induce an adaptive response of fetogenesis to a neutron challenge dose. Birth Defects Res (Part B) 83:502‐506, 2008. © 2008 Wiley‐Liss, Inc.