The Effect of Extreme Hypoxia on the Repair of DNA Single-Strand Breaks in Mammalian Cells

About 20 percent of the single-strand breaks produced by x rays in V79 Chinese hamster cells under extremely hypoxic conditions remain unrepaired after 1 hr at 37$sup 0$C. The corresponding figure is only 10 percent for cells irradiated under moderately hypoxic (0.2 $mu$M) or aerobic conditions (200 $mu$M). The initial number of breaks produced per unit dose is identical for extremely hypoxic and moderately hypoxic cells and is about four times greater for aerobic cells. Because split-dose recovery proceeds under aerobic and moderately hypoxic conditions and is inhibited only under extremely hypoxic conditions, the split- dose recovery phenomenon may be related to the unrepaired component of single- strand breaks. (auth)