Purpose: To investigate quantitatively the induction and rejoining of DNA double strand breaks (DSB) in V79-4 and xrs-5 Chinese hamster cells and HF19 human fibroblast cells, using the phosphorylation of the histone protein H2AX (gamma-H2AX) as an indicator of DSB, exposed to low doses of either low linear energy transfer (LET) (60)Co gamma-rays or high LET a-particles.
Materials and methods: Cells were irradiated with low or high LET (20 - 2000 mGy). The gamma-H2AX foci were detected using immunohistochemistry and quantified by image analysis.
Results: The number of DSB determined 30 min post gamma-irradiation at 37 degrees C is 12.2 (+/-1.5), 13.5 (+/-1.6) and 19.1 (+/-1.7) foci/cell/Gy for V79-4, xrs-5 and HF19 cells respectively, comparable with levels detected in V79-4 cells using pulse field gel electrophoresis. 6 h post gamma-irradiation, gamma-H2AX foci levels in V79-4 and HF19 cells approach control levels but remain higher in DSB repair deficient xrs-5 cells. Gamma-H2AX foci levels remain significantly higher than controls at 6 h in a-irradiated cells.
Conclusions: Gamma-radiation and alpha-radiation induced the phosphorylation of H2AX in response to DSB at low doses; the variation in the rate of dephosphorylation of induced foci are dependent both on radiation quality and cell characteristics.