Kinetics of Micronucleus Expression In Synchronized Irradiated Chinese Hamster Ovary Cells

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Abstract
The kinetics of expression of radiation-induced micronuclei (MN) in synchronized Chinese hamster cells (CHO) was examined. Does the cell cycle distribution of a population significantly influence the levels of radiation induced MN, thereby obscuring the exact quantification of the radiation effect? Cells were synchronized by centrifugal elutriation, irradiated, and then different phases of the cell cycle were examined for: cell cycle progression, division probability, and temporal expression of MN. The time interval for maximal MN expression is long enough that the position of cells in the cell cycle and radiation induced division delays do not prevent the majority of cells from completing their first post-irradiation mitosis, therefore expressing MN. By following the progression of synchronized cell populations by flow cytometry and also examining the time of division of individual cells for 24 h after irradiation, we observed that the maximum number of cells from all phases of the cell cycle are in their first post-irradiation interphase at that time, explaining the MN results.