A COMPARISON OF CELL SURVIVAL AND CHROMOSOMAL DAMAGE USING CHO CELLS SYNCHRONIZED WITH AND WITHOUT COLCEMID

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Abstract
Chinese hamster ovary (CHO) cells, synchronized in mitosis either by mechanical shaking or by chemical arrest with Colcemid, were X-irradiated at different times in the cell cycle and examined for both cell survival (ability to form colonies) and chromosomal damage. The investigation revealed that the two radiation responses were "age-dependent", viz., the proliferative ability of cells to form colonies was dependent upon the cyclic phase in which the cells were irradiated. Similarly, the extent of chromosomal damage and the types of radiation-induced chromosomal aberrations were also dependent upon the cyclic stage of the cells during irradiation. Cells synchronized by the aforementioned methods essentially gave the same results as borne out by statistical analysis despite the apparent indication that cells synchronized with Colcemid revealed a slight overall increase in radiation-induced chromosomal damage for all four cyclic phases. It was observed that cells irradiated in mitosis were most radiosensitive while cells irradiated during the DNA synthetic period were most resistant. A positive correlation between cell survival and chromosomal damage was observed which lends support to the theory that radiation-induced damage to chromosomes is primarily responsible for the loss of proliferative ability. However, the possibility that radiation-induced damage may be incurred by other cellular organelles, and this may to some degree be responsible for the loss of reproductive integrity, cannot totally be overlooked.