Radiation Response of Mammalian Cells Grown in Culture. IV. Dose Dependence of Division Delay and Postirradiation Growth of Surviving and Nonsurviving Chinese Hamster Cells

Abstract

Using an established line of Chinese hamster cells and 55 kv X rays, we have studied the postirradiation growth kinetics of initially log-phase cells after acute X-ray exposures. We found: 1) The division delays for surviving and nonsurviving cells are essentially equal and linearly dependent on dose; 2) the initial postdelay growth rates of the surviving and nonsurviving moieties are close to those of unirradiated cells (i.e., doubling time 8–9 hours); and 3) the number of divisions of which nonsurviving cells are capable varies approximately inversely with dose. Several deductions may be made from these results: 1) After moderate to large doses, survival is a much more sensitive indicator of radiation damage than division delay; 2) metabolic processes responsible for growth and division may be interrupted but are largely unimpaired by doses producing significant division delays and lethal effects; and 3) ascribing division delay to a “mitotic block,” which could be expected to lead to synchronous postdelay growth, is not indicated since asynchronous growth was observed. These results are discussed in the context of possible lethal mechanisms of ionizing radiations.—J Nat Cancer Inst 30: 705–721, 1963.