A modification of the micronucleus test and its use for evaluating the cytogenetic changes after irradiation

Foetal calf serum commonly used in the method of the micronucleus test was replaced with homologous mouse serum prepared in our laboratory. Using 0.2 ml of this serum per femur, the quality of the smears of bone marrow cells was comparable to that obtained by the original method. Long-term storage of mouse serum in frozen state (up to one year) did not affect the quality of the smears. Furthermore, we investigated the frequency of MN-PCE in the bone marrow of mice exposed to 1, 2.5, and 5 Gy of X-rays. The animals were examined at 3-h intervals from 6 to 48 h after irradiation. At 2.5 and 5 Gy, the frequency of MN-PCE reached the maximum values (about 7%) 27-39 h after irradiation. At 1 Gy, a marked increase in MN-PCE frequency occurred at 9-12 and 36-42 h after irradiation (about 3%, in both instances).