Flow cytometric analysis of micronucleus induction in mice by internal exposure to 137Cs at very low dose rates.

Internal radiation from 137Cs, intraperitoneally injected into mice, induced chromosome damage seen as micronuclei in erythrocytes of peripheral blood harvested 72 h after injection and analysed with flow cytometry. The retention of injected 137Cs activity was determined and the absorbed doses obtained from the beta-radiation of 137Cs were calculated for the whole bodies and bone marrow of the treated mice. The absorbed doses during the most relevant period for micronucleus induction were 2.7-18.3 mGy per day. The dose to the bone marrow during the same period was calculated to be 6-44 mGy per day. A linear dose response relationship was found.