Cellular and molecular repair of X-ray-induced damage: dependence on oxygen tension and nutritional status.

Cellular and molecular repair was studied at 23 degrees C using split-dose recovery and alkaline elution techniques, respectively, as a function of cellular oxygen and nutrient conditions. Hypoxic cells (0.001% O2) in full medium showed a partial reduction in the level of sublethal damage (SLD) repair relative to aerated cells (21% O2, OER equal to 3.2 relative to 0.001% O2); the respective repair kinetics were similar with a common repair half-time of 30 min. Similarly, hypoxic cells showed a slight reduction in strand break rejoining capacity compared to aerated cells. Under nutrient deprivation, anoxic cells displayed no SLD repair or strand break repair, while aerated cells exhibited the same level of SLD and strand break repair as for well-fed cells. In addition, nutrient deprived cells at low O2 levels (0.03%, OER equal to 1.15) displayed normal SLD and strand break repair capability. These results indicate that both nutrient and O2 deprivation are necessary for complete inhibition of cellular and molecular repair, and low levels of O2 (0.03%) can effectively reverse this inhibition.