Modelling of observed cellular radiosensitization in the presence and absence of oxygen when intracellular reducing species are concentration-modulated

Current versions of the chemical competition/radical repair model for the oxygen effect in radiation biology predict that, at high oxygen concentrations, cellular radiosensitization remains essentially invariant as the reducing (protecting) species S, in competition with oxidizing (damaging) species such as oxygen, is depleted to very low values. If species S is identified with endogenous intracellular thiols, experiments show that for some cell lines and thiol-depleting agents, radiosensitization under aerobic conditions increases with depletion. We have found that such variance can be predicted by modifying the assumption that all peroxyl target radicals lead to lethal lesions. (author)