Mitotic catastrophe induced by exposure of V79 Chinese hamster cells to low-energy protons

Purpose: To determine the yield of mitotic catastrophe induced after low energy proton irradiation and to compare this yield with that induced by X-rays. Materials: Asynchronous Chinese hamster V79 cells were irradiated with 0.5, 1, 2, 5 and 10Gy proton beams and X-rays. Proton LET of 7.7, 11.0 and 30.5keV mu m1, corresponding to energies of 5.01, 3.20 and 0.76MeV respectively, evaluated at the cell mid-plane, were used for experiments. The occurrence and yield of mitotic catastrophe was measured as the percentage of cells exhibiting fragmented nuclei. Results: Proton irradiation led to an enhanced induction of mitotic catastrophe in V79 cells. The onset of nuclear fragmentation, a hallmark of mitotic catastrophe, occurred much earlier after cell exposure to proton particles than to X-ray irradiation. Conclusions: Mitotic catastrophe is persistent in the subsequent cell generations after proton and X irradiation of V79 cells; but protons are more effective than X-rays for the induction of this phenomenon. These results are discussed in terms of their importance in space exposures and possible acquisition of genomic instability by the progeny of irradiated cells.