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W. Burkart, P. Heusser, Vijayalaxmi , Microdosimetric Constraints on Specific Adaption Mechanisms to Reduce DNA Damage Caused by Ionising Radiation, Radiation Protection Dosimetry, Volume 31, Issue 1-4, 1 June 1990, Pages 269–274, https://doi.org/10.1093/oxfordjournals.rpd.a080678
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Abstract
The protective effect of pre-exposure of lymphocytes to ionising radiation indicates the presence of 'adaptive repair' in mammalian cells. Microdosimetric considerations, however, raise some doubts on the advantage of such a cellular mechanism for specifically reducing the radiation damage caused by environmental exposures. Contrary to most chemicals which endanger the integrity of the mammalian genome, the local dose and dose rate from ionising radiation at the cellular level remain quite high, even at lowest exposures. A single electron or alpha particle passing through a cell nucleus already yields nuclear doses of up to about 3 mGy and 400 mGy, respectively. Macroscopic doses below these nuclear doses from a single event will only reduce the fraction of cell nuclei encountering the passage of a particle but not the dose or dose rate in the affected volume. At environmental doses in the range of 1 to 5 mGy per annum, the time between two consecutive hits in a specific cell nucleus is in the range of months to years, i.e. too long for the increased energy needs of adaptive responses to make sense. We find that very low concentrations of bleomycin, a clastogenic drug with high affinity to DNA, also triggers an adaptive response. This points to a more general stress response mechanism which may benefit the cell even at environmental levels of radioactivity, e.g. by protecting the integrity of DNA from attacks by chemicals, by endogenous radicals, by acids from anoxia, etc.
