Chromosomal damage in two X-ray irradiated cell lines: influence of cell cycle stage and irradiation temperature.

UNLABELLED The aim of this study was to investigate if irradiation with X-rays in different cell cycle phases resulted in a different response as measured with the micronucleus technique. In addition, the influence of irradiation temperature was investigated. MATERIALS AND METHODS Cells from a non-transformed human fibroblast cell line, HS2429, and a human breast cancer cell line, MCF-7, were synchronized by thymidine block and irradiated at either 2 degrees C or 37 degrees C in the G1-, S- and G2/M-phases. After cytokinesis-block by cytochalasin B, the frequency of micronuclei was determined. RESULTS Clear dose-response relationships were found. More micronuclei were detected in fibroblast cells irradiated in G1 and S than in G2/M, while the differences were not as prominent in MCF-7 cells. The irradiation temperature had no significant influence on the formation of micronuclei in either of the cell lines. CONCLUSION The formation of micronuclei varies with the cell cycle stage at the time of irradiation.