Induction of chromosomal aberrations and sister chromatoid exchanges by alpha particles in density-inhibited cultures of mouse 10T1/2 and 3T3 cells

Dose-response relationships were studied for induction of cell killing, chromosomal aberrations and sister chromatid exchanges (SCE) by 220 kV X-rays and 5.3 α-particles from a 238 Pu source. D0 values for X-ray and α-particle survival curves were 1.7 Gy and 0.7 Gy, and the extrapolation numbers 2.5 and 1.0 for mouse 3T3 cells. Chromosomal aberrations increased linearly with dose for α-radiation and roughly with the square of the dose for X-rays. At 37% survival, 1.0 aberration per cell was X-ray induced, 1.7 per cell by α radiation; the fraction without aberrations was similar. There was 50% reduction in X-ray induced aberrations in the first 4 h of confluent holding, but no decline in α induced aberrations up to 24 h. The dose-response relationship increased linearly up to 100cGy in 3T3 and 10T 1/2 cells, then declined to nearly background levels above 400cGy. SCE α induction increased rapidly with 2.5-5.0cGy then declined. RBE was 15-25 for SCE induction by 2.5-5.0cGy of α particles. (author)