A Comparison of Unscheduled DNA Synthesis, D 0 , Cell Recovery, and Chromosome Number in x-Irradiated Mammalian Cell Lines

Abstract

SHAEFl'EH, JAMES, AND MERZ, TIMOTHY. A Comparison of Unscheduled DNA Synthesis, Do, Cell Recovery and Chromosome Number in x-irradiated Mammalian Cell Lines, Radiat. Res. 47, 426-436. The relative extent of x-ray-induced unscheduled DNA synthesis was measured in seven mammalian cell lines: HeLa, mouse L-929, rat kangaroo kidney, human embryonic kidney, human laryngeal tumor, rat kangaroo liver, and human peripheral lymphocyte. Radiosensitivities (Do) and recovery ratios were measured in the HeLa, mouse L-929, and rat kangaroo kidney lines. There was no apparent correlation between unscheduled DNA synthesis and radiosensitivity or recovery ratio in these cell lines. These observations are consistent with the conclusion that cell survival after x-irradiation is not solely, if at all, dependent on unscheduled DNA synthesis. A correlation was observed between the relative amount of unscheduled DNA synthesis in the cell lines studied and their modal chromosome number. Cell lines containing more chromosomes showed greater amounts of unscheduled DNA synthesis. No correlation was apparent, however, when unscheduled DNA synthesis was compared with DNA content. One cell line, the rat kangaroo kidney line, showed no apparent unscheduled DNA synthesis. Whether this absence of unscheduled synthesis is the result of an enzymatic deficiency or is the natural consequence of a low chromosome number (11) is not clear and warrants further investigation. INTRODUCTON