Remarks on oxygen effects

Abstract

Oxygen concentration will influence theα- andβ-effect (two-component theory of radiation effects) independently. Theβ-effect is reduced by a dose-modifying factorγ. Oxygen, in competition with enzyme repair actions fortifies a part of theβ-lesions and this model leads to a simple equation for the factorγ. Theα-effect is also enhanced by oxygen. Measurements of OER indicate that the reduction of the effect from aerobic to anoxic condition might be about 70%. The functional dependence of oxygen concentration has not been investigated. For small oxygen concentrations of 0.15 to 0.5 µM/l and doses below 1000 R Révész and Littbrand have found that oxygen can protect the irradiated cells and thus increase survivals with about 10%. This is explained as a scavenger action where radical hydrogen atoms are oxidized and hydrated electrons captured by oxygen molecules. When the oxygen concentration is increased, or with higher doses, the usual sensitizing effect of oxygen exceeds the protection effect. The influence of oxygen onα-effects are mainly connected with indirect radiation effects and thus depend on temperature and milieu.