Inactivation of c3h 10t1/2 cells by monoenergetic high LET alpha-particles

Inactivation of mouse C3H 10t1/2 cells in plateau-phase (7.8 × 104 cells/cm2) was studied by using αparticles from the irradiation facility installed for radiobiological experiments at the 3 MV Tandem accelerator, University of Naples. Silicon detectors and CR39 plastic track detectors were employed for dosimetric purposes. The cells were exposed to high LET monoenergetic αparticles (energy of 1.8 MeV at the centre of the cell nucleus, track-averaged LET of 177 keV/μm and dose-rate of 1.1 Gy/min) and low-LET 80 kVp X-rays. The X-ray survival curve showed a significant shoulder (αbeta; = 9 Gy) while the survival curve for αparticles was close to exponential. The mean lethal dose of αparticles was 0.77 ± 0.02 Gy and the RBE was 5.2 at 80% survival and 3.0 at 5% survival. Survival of exponentially growing cells (2 × 104 cells/cm2) following irradiation with the αparticle beam is also reported. The nuclear areas of 10T1/2 cells were measured as 299 ± 9 μm2 and 250 ± 8 μm2 for cells in log phase and plateau phase, respectively. The inactivation cross-section, obtained from the mean lethal dose, was 34 μm2 and 37 μm2 for cells in log phase and plateau phase, respectively. These values appear to be the maximum measured values for the inactivation cross-section of 10T1/2 cells as a function of the αparticle LET. This saturation cross-section is very similar to the saturation values reported in the literature for other mammalian cell lines. © 1992 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.