Description of the damage mechanisms by Auger emitters at the cellular level and development of new radiation protection concepts taking into account the dependence of the radiation risk on the dose rate

Funded by: Federal Office for Radiation Protection, StSch30002.

Duration: 2008 - 2011

Responsible project leader: Dr. R. Kriehuber and Dr. E. Pomplun

Objectives

The aim of the study was to clarify, by means of investigations in cellular systems, to what extent a different dose rate during the decay of the Auger electron emitters (AEE) 123I and 125I qualitatively and quantitatively influences the resulting damage patterns. To this end, the biological endpoints to be investigated and quantified in SCL II and in kidney T1 cells were mainly apoptosis induction by annexin V/PI assay and chromatin damage by cytochalasin B micronucleus assay and neutral comet assay. In addition, gene expression analyses were planned at selected time points to provide information on the extent to which dose response affects the activation of various gene groups, particularly apoptosis-related and DNA repair-associated genes. Also addressed in this study was the question of whether bystander effects are induced with respect to apoptosis induction.

The model-theoretical part focused on the one hand on simulations of Auger electron spectra for validation of own Monte Carlo computational codes, recalculations of 123I and 125I decays based on them, and associated energy deposition calculations. On the other hand, quantum mechanical calculations were to be used to investigate the possibility of a Coulomb explosion and its molecular consequences.

Together, the experimental and model-theoretical investigations should serve to better describe the effect of the dose rate effect on cellular systems in vitro, to elucidate its cell physiological causes, and furthermore to help clarify the significance of the dose rate effect for radiation protection.