APOPTOSIS IS INDUCED IN THE SUBEPENDYMA OF YOUNG-ADULT RATS BY IONIZING IRRADIATION

To determine if radiation-induced apoptosis occurred in young adult br ain, we exposed 2-3-month old rats to single x-ray doses of 5 or 30 Gy . Apoptosis was quantified using the TdT-mediated dUTP-biotin nick end labeling (TUNEL) method and a morphologic assessment of nuclear fragm entation. Apoptosis occurred primarily in the subependyma but also in the corpus callosum, peaking 6 h after irradiation. At 48 h there were no apoptotic nuclei observed. These data are the first to show that a poptosis occurs in the young adult rat brain after ionizing irradiatio n. Further studies are required to define the particular cell type(s) involved and to address the role of this process in the pathogenesis o f late radiation injury.