Dosimetry and risk from low‐ versus high‐LET radiation of Auger events and the role of nuclide carriers

Abstract

Purpose: To analyse the lethality to mammalian cells of ¹²⁵I‐decays in DNA, in antipyrine in the whole cell and in oligodeoxynucleotides in the nucleus outside DNA as a function of Auger event‐site and number.

Materials and methods: Auger events cause both low‐ and high‐linear energy transfer energy depositions including charge neutralization at the daughter nuclide. Microdosimetry allows the expression of absorbed dose to a defined micromass and the number of such events at given sites. Published data were used to relate micromass dose and event number to the dose to reduce survival to 37% of the initial survival (D₃₇).

Results: The D₃₇ of ¹²⁵I‐decays in DNA was 0.1 Gy in terms of absorbed dose to the cell nucleus and about 30 in terms of average decays per nucleus or whole cell. The D₃₇ of ¹²⁵I‐decays in antipyrine was 1.5 Gy for absorbed dose to the cell nucleus, about 250 in terms of average decays per nucleus and about 2×10³ for average decays per whole cell. ¹²⁵I‐decays in oligodeoxynucleotides were much less toxic than ¹²⁵I‐decays in antipyrine by a factor of about 25 in terms of average absorbed dose to the cell nucleus, by a factor or about 40 in terms of average decays per cell nucleus and by a factor of six in terms of average decays per whole cell.

Conclusion: The unexpected low toxicity of ¹²⁵I‐decays in nuclear oligodeoxynucleotides outside the DNA in comparison with ¹²⁵I‐decays in antipyrine in the nucleus or the whole cell demands further attention on the role of oligodeoxynucleotides in altering cellular radiation sensitivity.