The usefulness of the micronucleus assay for investigating the radiation response of hepatocytes was examined. The frequency was defined as the ratio of the total number of micronuclei to the number of hepatocytes examined. The dose-response curves were curvilinear after X rays and linear after neutrons. These dose-response curves were analyzed by a linear-quadratic model, <tex-math>$\text{frequency}=aD+bD^{2}+c$</tex-math>. The a/b ratio was 3.03 ± 1.26 Gy following X irradiation. This value is within the range of the α/β ratios reported by others using the clonogenic assay of hepatocytes. While the a/b value for neutrons was 24.3 ± 11.7 Gy, the maximum relative biological effectiveness of neutrons was 6.30 ± 2.53. Since the micronucleus assay is simple and rapid, it may be a good tool for evaluating the radiation response of hepatocytes in vivo.

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