STUDIES ON THE MIGRATION OF MICRONUCLEATED ERYTHROCYTES FROM BONE-MARROW TO THE PERIPHERAL-BLOOD IN IRRADIATED SWISS MICE

Micronucleated polychromatic (mn-PCE) and normochromatic erythrocytes (nm-NCE) were enumerated in the bone marrow and peripheral blood of Swiss male mice at different time intervals following whole-body (I.0 Gy) gamma-irradiation. Polychromatic cells migrated to the peripheral blood soon after their formation in the bone marrow and mn-PCE achieved a frequency close to that of the bone marrow with a delay of about 12h. The optimal time for peripheral sampling was found to be about 36 h after radiation exposure. The frequency of mn-NCE in bone marrow and peripheral blood showed only a moderate and gradual increase till 60h, and was much lower in the latter. In another experiment, mice irradiated with 0.42 Gy gamma-rays (0.21 Gy/h) once a day for 5, 10 or 15 days (5 days per week) showed a cumulative dose-dependent increase in the levels of mn-NCE in the peripheral blood, sampled at 7 or 21 days after the last exposure. These observations demonstrate persistence and accumulation of mn-PCE in the peripheral blood of mice during repeated exposure to ionizing radiation, and the sampling could be delayed up to several days after the last exposure. Thus, peripheral mn-PCE, scored between 24-48h following irradiation, can be conveniently used to measure acute chromosomal damage induced by ionizing radiation in the bone marrow erythroblasts of mice, while peripheral mn-NCE are suited to monitor accumulated damage during chronic/repeated exposure.