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 polychrom atic erthrocytes (PCEs) from bone marrow (BM) and peripheral blood (PB ) of mice after four different treatments were determined by flow cyto metry. PCEs were differentiated from normochromatic erythrocytes (NCEs ) using the fluorescent RNA stain Thiazole orange, while MN in erythro cytes were detected with the DNA stain Hoechst 33342. The treatments w ere X-irradiation (1 Gy), cyclophosphamide (CPA; 30 mg/kg), vincristin e sulphate (VCR; 0.08 mg/kg), and cholchicine (COL; 1 mg/kg). Afl trea tments showed increased frequencies of micronucleated PCEs at 30 h aft er treatment in BM and at 50 h in PB. The clastogens (X-irradiation an d CPA) and the spindle poisons (VCR and COL) could be grouped accordin g 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 la rge (2-10%) MN. In PB the relative frequency of large MN was lower tha n in BM, indicating that they were partly eliminated before entrance i nto the peripheral circulation.