RBE for the induction of apoptosis in human peripheral lymphocytes exposed in vitro to high-LET radiation generated by accelerated nitrogen ions.
OBJECTIVE
To investigate the relative biological effectiveness (RBE) of accelerated nitrogen ions (32-45 MeV/u) compared with 137Cs gamma-rays for the induction of apoptosis in G0 lymphocytes.


METHODS
Human peripheral G0 lymphocytes were exposed in vitro to doses up to 3 Gy. RBE for the induction of apoptosis was studied at different times after irradiation (0, 24, 48 and 72 h) with the use of three different methods: (1) morphological characterization of apoptotic cells after fluorescence staining; (2) cell size distribution analysis of the cell population to detect apoptotic bodies; and (3) electrophoretic analysis of DNA to detect 'DNA-ladders'.


RESULTS
RBE values in the range of 1.3-3.0 were obtained from the linear components of the dose response curves. The variation in RBE was primarily dependent on post-irradiation time, where the highest RBE values were obtained after 48 h. The three different techniques used for analysis of apoptosis gave similar results. The significantly increased RBE was also seen as an earlier appearance of DNA-ladders, as well as a more rapid disappearance of the total number of viable cells.


CONCLUSIONS
These results show that nitrogen ions of high linear energy transfer (LET) produce RBE > 1.0 and induce a faster apoptotic response as compared with gamma-photons of low-LET radiation.
Meijer
A E
AE
Swedish Radiation Protection Institute, Stockholm.
Kronqvist
U S
US
Lewensohn
R
R
Harms-Ringdahl
M
M
D017209:Apoptosis / Q000528:radiation effects*; D002453:Cell Cycle / Q000528:radiation effects; D002463:Cell Membrane Permeability / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D007477:Ions; D018499:Linear Energy Transfer; D008214:Lymphocytes / Q000166:cytology / Q000528:radiation effects*; D009584:Nitrogen; D010315:Particle Accelerators; D012062:Relative Biological Effectiveness
D007477:Ions; D009584:Nitrogen