High- and low-LET induced chromosome damage in human lymphocytes: a time-course of aberrations in metaphase and interphase

Purpose: To investigate how cell-cycle delays in human peripheral lymphocytes affect the expression of complex chromosome damage in metaphase following high- and low-LET radiation exposure. Materials and methods: Whole blood was irradiated in vitro with a low and a high dose of 1 GeV u(-1) iron particles, 400 MeV u-1 neon particles or gamma -rays. Lymphocytes were cultured and metaphase cells were collected at different time points after 48 84 h in culture. Interphase chromosomes were prematurely condensed using calyculin-A, either 18 or 72 h after exposure to iron particles or gamma -rays. Cells in first division were analysed using a combination of FISH whole-chromosome painting and DAPI/Hoechst 33258 harlequin staining. Results: There was a delay in expression of chromosome damage in metaphase that was LET- and dose-dependent. This delay was mostly related to the late emergence of complex-type damage into metaphase. Yields of damage in PCC collected 48 h after irradiation with iron particles were similar to values obtained from cells undergoing mitosis after prolonged incubation. Conclusion: The yield of high-LET radiation-induced complex chromosome damage could be underestimated when analysing metaphase cells collected at one time point after irradiation. Chemically induced PCC is a more accurate technique since problems with complicated cell-cycle delays are avoided.