Phosphorylation of histone H2AX in peripheral blood mononuclear cells after thoracic irradiation of rats

Abstract

Summary Lymphocytes are among the most radiosensitive cells. After exposure of the organism to ionizing radiation, they promptly die by apoptosis at a rate proportional to the dose received. Because of this, they are frequently used in biodosimetry. We demonstrated that one hour after whole-body irradiation of rats, histone H2AX in the lymphocyte nuclei was quickly phosphorylated on serine 139, the phosphorylation process being directly dependent on the gamma radiation dose. In the work presented here, we studied the kinetics of lymphocyte depletion in the peripheral blood and phosphorylation of histone H2AX in the peripheral blood lymphocytes after local (thoracic) irradiation of rats. Twenty-four hours after whole-body irradiation of the rats at a dose of 5 Gy, the lymphocyte count declined to almost zero values, whereas after local irradiation of the thorax area, the counts of lymphocytes in the peripheral blood remained unaltered. The authors employed two methods (flow-cytometric and microscopic) for the γH2AX determination in the peripheral blood lymphocytes, 1 h after thoracic irradiation of rats. Flow cytometry revealed a dose dependence on the increase in γH2AX in a dose range of 10–30 Gy. The microscopic method was more sensitive in the case of lower radiation doses, the dependence on the dose being obvious from a dose as low as 5 Gy. The methods are able, in the dose range 5–30 Gy, to differentiate between the type of irradiation, i.e. the whole-body or local.