Influence of Prior Exposure to Low-Dose Adapting Radiation on Radiation-Induced Teratogenic Effects in Fetal Mice with Varying Trp53 Function

Teratogenesis in tails and limb digits of fetal mice with varying Trp53 status was examined after exposure of pregnant females to 4 Gy gamma radiation with and without a prior 30-cGy exposure. Prior low-dose exposure modified the teratogenic effects of radiation in a manner dependent upon Trp53 status and gestation time. A 4-Gy exposure on gestation day 11 resulted in tail shortening and digit abnormalities. A 30-cGy exposure 24 h prior to a 4-Gy radiation exposure on day 11 reduced the extent of both digit abnormalities and the tail-shortening effects in Trp53(+/+) fetuses and also reduced tail shortening in Trp53(+/-) fetuses, but to a lesser extent. However, the pre-exposure enhanced the tail-shortening effects of 4 Gy in Trp53(-/-) fetuses. In contrast, a 30-cGy exposure given 24 h prior to a 4-Gy exposure on gestation day 12 had no effect on the reduced tail length resulting from the 4-Gy exposure of Trp53(+/+) or Trp53(+/-) fetuses, but it partly protected Trp53(-/-) fetuses against reduced tail length. A 4-Gy exposure alone on day 12 did not result in any increase in the frequency of digit abnormalities in Trp53(-/-) fetuses so any protective effect of the preirradiation could not be detected. However, the preirradiation did result in protection against in digit abnormalities in Trp53(+/-) fetuses. We conclude that radiation-induced teratogenesis reflects both Trp53-dependent and independent processes that lead to apoptosis, and these respond differently to prior adapting doses.