Analysis of Cell Cycle in Mouse Bone Marrow Cells Following Acute in vivo Exposure to ^<56>Fe Ions

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A pilot study was conducted to examine the magnitude of cell-cycle delay and apoptosis in bone marrow (BM) cells collected at 18, 42 and 66 hr from radiosensitive CBA/CaJ mice and radioresistant C57BL/6J mice following a whole-body in vivo exposure to 1 GeV/amu ^<56>Fe ions or ^<137>Cs γ rays. At each sacrifice, BM cells were collected from three mice of each strain per dose of ^<56>Fe ions (0, 10 and 100 cGy) and two mice of each strain per dose of ^<137>Cs γ rays (0, 100 and 300 cGy). A significant G1-arrest (ANOVA, p < 0.05) was observed at 18 hr after exposure of mice to 100 cGy of ^<56>Fe ions or 300 cGy of ^<137>Cs γ rays, relative to their corresponding sham-controls, resulting in a significant decrease in the percentage of cells cycling into S-phase in both strains. The percentage of S-phase cells subsequently increased and persisted up to 66 hr post-irradiation. Significant numbers of G2/M cells were found at 18 and 66 (but not at 42) hr post-irradiation, regardless of radiation-type or mouse-strain. It is likely that BM cells have undergone at least one cell cycle at 66 hr after exposure of mice to either 100 cGy ^<56>Fe ions or 300 cGy ^<137>Cs γ rays. Our study is the first to investigate the in vivo effects of ^<56>Fe ions (1 GeV/amu) on the cell cycle of mouse BM cells using flow cytometry. The cell-cycle distribution (but not the number of apoptotic cells) was dependent on radiation-dose and harvest-time.
2008-07-16