OPPOSITE TRENDS OF CHANGES IN REACTIVE BEHAVIORS OF MACROPHAGES AND ASTROCYTES FOLLOWING GAMMA-IRRADIATION PERFORMED AT DIFFERENT STAGES OFPRENATAL DEVELOPMENT - A STUDY IN THE INJURED BRAIN OF 6-DAY-OLD RAT

Pregnant Wistar rats were exposed to a single 1.0 Gy dose of gamma ray s on gestational days 13, 15, 17 or 19 (E13s, E15s, E17s and E19s, res pectively). A mechanical injury was made in the cerebral hemisphere of their 6 day-old male offsprings. The injured rats were injected with [H-3] thymidine on day 1 or 2 after injury and killed 4 h after the in jection. Brain sections were processed for BSI-B4 isolectin histochemi stry, subjected to autoradiography and examined microscopically to rec ord numbers of proliferating and unproliferating macrophages located w ithin the region of injury. The total number of macrophages as well as number of their divisions were minimal in E13s then showed a regular increase in E15s and E17s, and reached its maximal level in brains irr adiated on E19. The trend of changes was opposite to that showed by ch anges in the intensity of astrocyte proliferation [Z. Setkowicz, K. Ja neczko, Effects of prenatal gamma-irradiation on the astrocyte prolife ration in response to injury in the brain of 6-day-old rat, Brain Res. 803 (1998) 122-128.]. The recruitment and proliferation of macrophage s and the astrocyte proliferation were regarded as reactive processes occurring under control of different regulatory mechanisms acting with in the region of injury. (C) 1998 Elsevier Science B.V. All rights res erved.