The effect of low-level prenatal X-irradiation on postnatal development in the Wistar rat

The objective of this investigation was to determine the effect of low-dose prenatal X-irradiation on postnatal growth and neurobehavioral development, and whether alterations would manifest at dosages lower than those which produce anatomic malformations from exposure at the most sensitive period of organogenesis. Ninety-eight Wistar strain rats were exposed to 0.1, 0.2, or 0.4 Gy X-radiation of were sham irradiated on the 9th or 17th day of gestation. A conventional teratologic evaluation was completed on half of the animals (572 fetuses). The age of appearance of four physiologic markers and of acquisition of six reflexes was observed in 372 offspring. Exposure during early organogenesis at these levels had no effect on any of these parameters. Prenatal exposure to X-radiation on the 17th day of gestation at dosage levels greater than 0.1 Gy resulted in alterations in the appearance of three postnatal neurophysiologic parameters. Growth retardation throughout the postpartum period also was observed in the offspring. The induction of developmental and reflex alterations had a comparable threshold to the known threshold for anatomic malformations on the 9th day. These results indicate that all of the parameters studied had thresholds either at or above 0.2 Gy acute radiation, and that the postpartum developmental and reflex acquisition measures were not more sensitive indicators of exposure to X-radiation than growth parameters.