The Dependence on Radiation Quality of the Repair of Potentially Lethal Damage

Stationary mammalian cells have been shown to have an efficient repair of potentially lethal damage (PLD) after irradiation with sparsely ionising radiation but very little PLD repair after irradiation with more densely ionising radiation of 390 keV.µm-1. Yeast, on the contrary, shows an efficient PLD repair for both sparsely ionising radiation and more densely ionising radiation up to 490 keV.µm-1 and the PLD repair only begins to decrease after irradiation with very densely ionising radiation above 1930 keV.µm-1. In previous publications we have made the association between DNA double strand breaks and PLD. In this paper we show that by considering the induction and repair of DNA double-strand breaks as a function of radiation quality we can resolve the paradox between the PLD repair in yeast and mammalian cells. Furthermore, we can conclude that the lack of experimental evidence for the repair of PLD in mammalian cells from densely ionising raiation does not necessarily imply that there is no repair of the potentially lethal lesion.