Dosimetry and risk from low- versus high-LET radiation of Auger events and the role of nuclide carriers.
OBJECTIVE
To analyse the lethality to mammalian cells of (125)I-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.


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 (125)I-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 (125)I-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 x 10(3) for average decays per whole cell. (125)I-decays in oligodeoxynucleotides were much less toxic than (125)I-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.


CONCLUSIONS
The unexpected low toxicity of (125)I-decays in nuclear oligodeoxynucleotides outside the DNA in comparison with (125)I-decays in antipyrine in the nucleus or the whole cell demands further attention on the role of oligodeoxynucleotides in altering cellular radiation sensitivity.
Feinendegen
L E
LE
Brookhaven National Laboratory, Upton, NY, USA.
Neumann
R D
RD
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D002467:Cell Nucleus / Q000528:radiation effects; D002468:Cell Physiological Phenomena / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D004247:DNA / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004583:Electrons; D006801:Humans; D007457:Iodine Radioisotopes / Q000009:adverse effects*; D018499:Linear Energy Transfer / Q000502:physiology*; D009841:Oligonucleotides / Q000378:metabolism* / Q000528:radiation effects; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors
D007457:Iodine Radioisotopes; D009841:Oligonucleotides; D004247:DNA