Effects of prenatal gamma-irradiation on the astrocyte proliferation in response to injury in the brain of 6-day-old rat.

Pregnant Wistar rats were exposed to a single 1.0 Gy dose of gamma rays on gestational days 13, 15, 17 or 19 (E13, E15, E17 and E19, respectively). A mechanical injury was made in the cerebral hemisphere of their 6 day-old male offsprings. The injured rats were injected with [3H]thymidine on day 1 or 2 after injury and killed 4 h after the injection. Brain sections were immunostained for glial fibrillary acidic protein (GFAP) or S-100beta protein, subjected to autoradiography and examined microscopically to record proliferating astrocytes. The intensity of astrocyte proliferation in response to injury showed a gradual decrease from the level maximal in brains irradiated on E13 to minimal in those irradiated on E19. The changes were regarded as being related to the stage of prenatal development when irradiation of the brain was performed.