THE EFFECT OF OXYGEN ON LOW-DOSE HYPERSENSITIVITY AND INCREASED RADIORESISTANCE IN CHINESE-HAMSTER V79-379A CELLS

Chinese hamster V79 cells irradiated in air are hypersensitive to X-ra y doses less than 0.5 Gy and show an increased radioresistance over th e dose range 0.5-1 Gy (Marples and Joiner, Radiat. Res. 133, 41-51, 19 93). Of considerable interest from both a mechanistic and clinical vie wpoint is the response of hypoxic cells over this dose range. The data presented here indicate that hypoxic cells are also hypersensitive to low X-ray doses and exhibit an increased radioresistant response, alb eit triggered at a somewhat higher dose (0.69 Gy, SEM +/- 0.18 Gy) tha n observed in oxygenated cells (0.5 Gy, SEM +/- 0.21 Gy). These data i ndicate that the triggering event for increased radioresistance may be independent of oxygen. As reported by others previously, the oxygen e nhancement ratio was found to decrease with a decreasing X-ray dose.