[Changes of chromatin structure state in thymocites at the early stage of apoptosis induced by hydrogen peroxide and radiation]

The paper deals with changes in the structural state of chromatin in isolated thymocites at the early stage of apoptosis induced by hydrogen peroxide and radiation. Content of necrosis and apoptosis cells in the suspension of the isolated rat thymocites, during 3-hour incubation after X-ray irradiation in a dose of 4.5 Gy or with the presence of 0.1 microM of H2O2 by the method of double lifetime staining by fluorescent dye Hehst 33342 and propydium iodide has been estimated. Apoptogenic effect of the studied effects has been found out, the dynamics of condensation and internucleosomic chromatin fragmentation has been established. It has been shown that 100 microM alpha-tocopherol inhibited completely DNA fragmentation in the cells incubated with H2O2 and only partially in irradiated cells. Introduction of postmitochondrial supernatant, isolated from the incubated control or irradiated cells, into the cell-free system which included the ATP-regenerating system and nuclei of control thymocites did not affect the level of DNA fragmentation, while the increase of the level of fragmented DNA in nuclei was observed in the presence of the supernatant obtained by centrifugation of the cells treated by H2O2. Differences of mechanisms of thymocite apoptosis initiation, as affected by hydrogen peroxide and ionizing radiation, is discussed.