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 en ergy proton irradiation and to compare this yield with that induced by X-ra ys. Materials: Asynchronous Chinese hamster V79 cells were irradiated with 0.5, 1, 2, 5 and 10 Gy proton beams and X-rays. Proton LET of 7.7, 11.0 and 30. 5 keV mu m(-1), corresponding to energies of 5.01, 3.20 and 0.76 MeV respec tively, evaluated at the cell mid-plane, were used for experiments. The occ urrence 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 catastr ophe in V79 cells. The onset of nuclear fragmentation, a hallmark of mitoti c catastrophe, occurred much earlier after cell exposure to proton particle s than to X-ray irradiation. Conclusions: Mitotic catastrophe is persistent in the subsequent cell gener ations after proton and X irradiation of V79 cells; but protons are more ef fective than X-rays for the induction of this phenomenon. These results are discussed in terms of their importance in space exposures and possible acq uisition of genomic instability by the progeny of irradiated cells.