Induction of micronuclei by acute and chronic exposure in vivo to gamma rays in murine polychromatic erythrocytes.

The effect on micronuclei (MN) frequency of in vivo exposure to different dose rates of gamma rays in murine polychromatic erythrocytes (PCE) was studied. Groups of animals were irradiated with 1.0 Gy of gamma rays administered in 10, 100, 1000 or 10,000 min; the micronucleated polychromatic-erythrocytes (MN-PCE) frequency was scored in blood samples obtained from the tail of mice at various times before, during or after irradiation. The time-response curves for the 10, 100, and 1000 min exposure were similar; however, the two first curves showed a peak at 1800 min and the last at 2400 min after exposure. The curve obtained from the 10,000 min exposure showed a plateau for a long period during and after the exposure. However, the integration of the area under the curves indicates that the damage caused by the different radiation protocols was the same, suggesting that throughout time, the lesions were not repaired but rather diluted by cell division.