ERYTHROPOIESIS AND THE INDUCTION OF MICRONUCLEI IN MOUSE SPLEEN DETERMINED BY FLOW-CYTOMETRY

Erythrocytes from the spleen of CBA mice have been prepared for analys es by flow cytometry. About 80% of the polychromatic erythrocytes (PCE ) in the spleen originate from erythropoiesis in the spleen, while the remaining 20% come from the peripheral blood. Analyses of the RNA con tent of PCE revealed that splenic PCE do not mature into normochromati c erythrocytes (NCE) in the spleen but leave the organ at a more immat ure stage. A considerable part of the PCE from bone marrow also mature into NCE in the bone marrow. The rate of RNA breakdown in PCE follows an exponential function. Time-courses for the appearance of micronucl eated PCE (MPCE) from spleen and from bone marrow were determined by a nalysis of samples taken with short intervals after an acute dose of 0 .1 Gy X-rays. The time-courses were identical for MPCE from the spleen and the bone marrow: The frequency of MPCE (fMPCE) starts to increase at about 10 h after irradiation and reaches its maximum after about a nother 20 h, upon which fMPCE returns to control level. The first indu ced MPCE in peripheral blood appear at about 20 h after irradiation. T he effects of the carcinogen DMBA, 9,10-dimethyl-1,7-benzanthracene, a t low doses were determined in PCE from spleen and bone marrow. The se nsitivity was found to be about the same for erythroblasts in the sple en and the bone marrow. Protracted exposure to gamma-irradiation at a very low dose rate (44 mGy/day) gave a similar increase of fMPCE in bo ne marrow and spleen. The suitability of using splenic erythrocytes in the micronucleus test is discussed. (C) 1997 Elsevier Science B.V.