The micronucleus assay of lymphocytes is a useful predictive assay of the radiosensitivity of normal tissue: a study of three inbred strains of mice.

Radiation sensitivity was measured by the micronucleus assay in T lymphocytes of the spleen and in fibroblasts derived from three inbred strains of mice, BALB/c, A/J and C3H/He. A linear correlation between the surviving fraction and the micronucleus frequency was obtained. There were clear differences in the radiosensitivity of T lymphocytes and of fibroblasts from the different strains of mice. T lymphocytes and fibroblasts from BALB/c mice were more radiosensitive than those from A/J and C3H/He mice. To explore the correlation between the radiosensitivity of T lymphocytes and of fibroblasts in vitro and the reaction of normal tissue to radiation, the survival ofjejunal crypt stem cells from the three mouse strains was determined using a microcolony assay. The jejunal crypt cells of BALB/c mice were more radiosensitive than those of A/J and C3H/He mice. Thus the order of radiosensitivity of T lymphocytes and fibroblasts in vitro corresponds to the sensitivity ofjejunal crypt cells in vivo. Our results suggest that determining the radiosensitivity of T lymphocytes and fibroblasts in vitro may be useful in predicting the magnitude of radiation-induced damage in the small intestine.