Effect of gamma radiation at high- and low-dose rate on a novel in vivo mutation assay in mouse intestine

The present investigation characterizes the responses of F1 mice to high- and low-dose rate gamma radiation (1.8 and 0.01 Gy/min respectively) and shows that the induction of ribbons is dose dependent in both cases. Dose sparing is evident at the lower dose rate: 20 ribbons/104 villi can be induced by 4 Gy at high-dose rate and by 7.1 Gy at low-dose rate, a dose sparing of 1.76. Age-matched untreated mice had a background level of 3.7 ribbons/104 villi. As expected, no ribbons were observed in homozygous (Dlb-1b/Dlb-1b) C67BL/6J mice, in which each stem cell has two alleles specifying lectin binding. The results further validate this system as a sensitive in vivo mutagenicity assay and suggests that the target cells are capable of repairing radiation damage. (author)