G2-delay after irradiation with alpha-particles as studied in synchronized cultures and by the bromodeoxyuridine-33258H technique.

Division delay of mouse L-929 fibroblasts after alpha-irradiation is due to a pronounced lengthening of their G2-phase. Experiments on synchronously and asynchronously growing cultures revealed a cell cycle phase-dependent sensitivity of this effect: Cells irradiated in G2 or at the G1/S border suffered a longer G2-delay than cells irradiated at mid- or late-S. Progression through G2 was nearly normal at doses up to 0.3 Gy if cells were exposed during G1 phase.