Radiation sensitization of E. coli B/r by mixtures of oxygen and nitrous oxide

The authors have measured the radiation sensitivity in mixtures of N2O and O2 to observe additivity patterns and to determine if these two agents have any common processes for sensitization. It was found that some low O2 concentrations do not increase the response in N2O, although they can have significant sensitizing effects in N2. This lack of additivity is taken as evidence for a common mechanism of damage from N2O and low concentrations of O2. In contrast, damage from high concentration of O2 is additive to the damage from N2O. The greatest sensitivity, observed with a gas mixture of about 15% O2/85% N2O, is equivalent to the response in 100% N2 plus the maximum amount of damage O2 can cause plus the maximum amount of damage N2O can cause. This additivity is taken as evidence that N2O and high concentrations of O2 sensitize in different ways. Thus, O2 is known to sensitize these bacteria in at least two different ways; one of these is apparently also the way N2O sensitizes. (author)