The survival of cytochalasin-induced multinucleation following irradiation of Chinese hamster ovary cells.

Chinese hamster ovary cells were cultured for up to 280 hr in medium containing 1.75 mcg/ml cytochalasin B. The distribution of the number of nuclei per cell in unirradiated cultures on the 6th day was unimodal with some cells containing 27 or more nuclei. The DNA content distribution was in contrast polymodal with the means of the two terminal major peaks occurring at approximately 40 and 80 units of DNA content (antimodes at 29 and 58 units), where 1 unit is the content of untreated G1 cells. Irradiation (gamma, 137-Cs) at doses up to 10 Gy caused an exponential reduction in the proportion of plated cells able to reach high nucleus- or DNA-contents. The reduction due to 5 Gy was stable at least up to 280 hr in culture. The accumulation of total DNA in the culture was well-fitted by a Gompertz function, with little further increase after 230 hr when the average DNA content per cell reached about 90 units.