Radio-induced structural membrane modifications: a potential bioindicator of ionizing radiation exposure?

Purpose: This study focused on radio-induced membrane alterations in order to assess some related parameters as potential biological indicators of ion izing radiation effects in cases of accidental overexposure. Materials and methods: Radio-induced membrane alterations were assessed aft er gamma-irradiation of human blood. Biophysical techniques based on fluore scent probe incorporation into isolated living lymphocytes and erythrocytes membranes were applied. Results: Using the technique of fluorescence polarization, the lipophilic p hase of the membrane was shown to be more fluid whereas the lipid-protein i nterface of the membrane was shown to be more rigid after gamma-irradiation . Fluorescent anisotropy modifications showed dose-time effect relationship s after radiation exposure. Ionizing radiation induced a decrease in steady -state anisotropy values but did not affect the probe's lifetime as assesse d by fluorescence lifetime distribution technique. These data suggest that the anisotropy variations are representative of the local properties of the fluorescent probe's micro-environment. However, the distribution width sho wed a decrease pointing towards radiation-induced changes of membrane domai n organization, probably due not only to membrane water penetration related to lipoperoxidation, but also to compositional changes and redistribution of membrane components. In contrast, the lack of radiation effect observed using the lateral diffusion index technique may be related to the integrate d overview of the radio-induced modifications of the membrane provided by t his technique, which pointed out radio-induced damage to the membrane in mi cro-domains. Conclusion: These findings suggest the utility of structural membrane modif ication measurements as an early bio-indicator of ionizing radiation exposu re.