An ionizing radiation-sensitive mutant of CHO cells: irs-20. II. Dose-rate effects and cellular recovery processes.

An ionizing radiation-sensitive mutant of CHO cells, irs-20, irradiated in plateau-phase cultures showed a complete lack of a dose-rate effect, i.e., there was no reduction in cell killing per unit dose as the dose rate was lowered from 0.75 Gy/min to 0.06 Gy/h. No measurable repair of potentially lethal damage or sublethal damage was evident for irs-20 cells in the G1 phase of the cell cycle. During S phase, irs-20 cells showed repair of sublethal damage similar to that for the wild-type cells.