RADIATION-INDUCED MICRONUCLEUS FORMATION IN MOUSE BONE-MARROW AFTER LOW-DOSE EXPOSURES

The incidence of micronucleus formation was studied at 12, 24 and 36 h post-irradiation in the polychromatic (PCE) and normochromatic (NCE) erythrocytes of the bone marrow of mice whole-body exposed to 0, 3, 9, 18, 36, 54 and 72 cGy of Co-60 gamma-radiation. It was observed that the frequency of micronucleated polychromatic erythrocytes (MPCE) incr eased with the increase in exposure dose at all the post-irradiation t ime periods studied. similarly, the frequency of micronucleated normoc hromatic erythrocytes (MNCE) also increased with the increase in expos ure dose and the increase for both MPCE and MNCE was dose related. The dose-response relationship was linear-quadratic for both MPCE and MNC E. The study of mitotic index revealed that a dose as low as 9 cGy is capable of reducing the mitotic index significantly at 24 h post-irrad iation and the dose response was linear-quadratic. However, no signifi cant decline in the mitotic index was observed at 12 and 36 h post-irr adiation.