THE TIME-COURSE OF MICRONUCLEATED POLYCHROMATIC ERYTHROCYTES IN MOUSEBONE-MARROW AND PERIPHERAL-BLOOD

The time-course of micronucleated polychromatic erythrocytes (MPCE) in mouse bone marrow and peripheral blood, induced by an acute 0.1 Gy do se of X-rays, was determined using flow cytometric analysis, which mad e frequent sampling possible and allowed use of a dose low enough not to affect erythroid cell proliferation. The frequency of MPCE (fMPCE) began to increase in the bone marrow at 10 h after irradiation and rea ched a maximum at 28 h after irradiation. In the peripheral blood fMPC E began to increase at 20 h after irradiation and peaked at about 40 h after irradiation. The time-course found is discussed on the basis of data on the differentiation of erythroid cells. The results indicate that the micronuclei registered in polychromatic erythrocytes may orig inate from lesions induced not only during the last cell cycle but als o during earlier ones. After an acute dose of 1.0 Gy of X-rays the max imum fMPCE was delayed both in bone marrow and peripheral blood reflec ting an effect on the cell cycle progression of erythroblasts.