DNA content determination of micronucleated polychromatic erythrocytes induced by clastogens and spindle poisons in mouse bone marrow and peripheral blood.

The frequencies and DNA distributions of micronuclei (MN) in polychromatic erthrocytes (PCEs) from bone marrow (BM) and peripheral blood (PB) of mice after four different treatments were determined by flow cytometry. PCEs were differentiated from normochromatic erythrocytes (NCEs) using the fluorescent RNA stain Thiazole orange, while MN in erythrocytes were detected with the DNA stain Hoechst 33342. The treatments were X-irradiation (1 Gy), cyclophosphamide (CPA; 30 mg/kg), vincristine sulphate (VCR; 0.08 mg/kg), and cholchicine (COL; 1 mg/kg). All treatments showed increased frequencies of micronucleated PCEs at 30 h after treatment in BM and at 50 h in PB. The clastogens (X-irradiation and CPA) and the spindle poisons (VCR and COL) could be grouped according to the fluorescent characteristics of the induced MN as well as the relative frequency of small (0.5-2% of the diploid DNA content) and large (2-10%) MN. In PB the relative frequency of large MN was lower than in BM, indicating that they were partly eliminated before entrance into the peripheral circulation.