Target cells of apoptosis in the adult murine dentate gyrus and O4 immunoreactivity after ionizing radiation

The occurrence of radiation-induced apoptosis and the determination of targ et cells were investigated by using the TdT-mediated dUTP-biotin nick end l abeling assay and immunohistochemical analyses. The O4 immunoreactivity, an oligodendrocytes surface antigen, was also evaluated by using western blot ting analysis. C57BL/6J adult female mice were subjected to single dose irr adiation of 10 Gy. Eight hours after irradiation, the most significant incr ease of apoptotic cells was detected in the subgranular zone and the hilus of the dentate gyrus. The target cells of radiation-induced apoptosis are t he subgranular progenitor cells and the oligodendrocytes in the hilus. The amount of the O4 immunoreactivity, a marker for premature oligodendrocytes, was unchanged until 8 h but enhanced after 12 h of irradiation. These resu lts are the first to show the increase of the O4 immunoreactivity after irr adiation and may be associated with the pathogenesis of radiation injury. ( C) 2000 Elsevier Science Ireland Ltd. All rights reserved.