Radiation responses in air-, nitrous oxide-, and nitrogen-saturated mammalian cells

Characteristics of cellular radiation chemistry were studied for mammalian cells saturated with air, nitrous oxide, or nitrogen in the absence or presence of an OH-radical scavenger, for both low- and high-LET radiations. For clarity, the data for low-LET studies are presented separately in this paper, while the results for densely ionizing particle radiations will be discussed in a subsequent manuscript. Cell monolayers were grown in glass vessels and irradiated with 225-kVp X rays. The contribution of OH-radical action was reduced from about 55% in aerobic cells to about 20% in nitrogen-saturated cells. In nitrous oxide-saturated cells, the indirect effect attributable to OH. is about 35%. OH-radical-mediated lesions can therefore result in oxygen-independent as well as oxygen-dependent lesions. Our results show that the hydrated electron does not contribute significantly to radiolethality in anaerobic cells