Abstract
In order to clarify the sites in a cell which were susceptible to oxygen effect by radiation, its effect on the membrane permeability of sheep erythrocytes was investigated with 200 kVp X-rays and 6 MeV cyclotron neutrons in the presence and absence of oxygen. Radiation damage to membranes, irradiated at room temperature and stored for 20 hours at 4° and 37°C, was assessed from both the escape of K+ from the cells and the incorporation of Na+ into the cells. The values of OER (oxygen enhancement ratio) and RBE (relative biological effectivenss) for the damage by neutrons at 4°C were 1.0 and 3.1, respectively. The same value of OER was obtained by X-rays. No oxygen effect was also observed even at 37°C where the repair of damage to membranes existed.
These results are incompatible with the model that membranes are sites of type ‘O’ damage susceptible to oxygen effect.
