Effects of prenatal irradiation on fetal, neonate, and young adult murine hemopoiesis

B6D2F1 mice received cobalt-60 radiation on day 10.5 of gestation at doses of 50 to 300 rad at a dose rate of 40 rad per min. These animals were studied at four selected age periods: (a) day 14.5 of gestation, (b) neonate, (c) juvenile, and (d) 13 week-old adult. Fetal liver cellularity, morphology, and hemopoietic progenitor cell concentration reflected injury after 200 rad. The 15 day-old mouse spleen cellularity was affected more than bone marrow cellularity, but greater radiation injury was reflected by bone marrow hemopoietic progenitor cells. Fluctuations from normal hematopoietic values were greater in the 15 day-old juvenile than in the 9 day-old neonate, commencing with 50 rad. These included peripheral blood parameters and marrow- and spleen-derived erythroid-, granulocytic- and megakaryocytic-progenitor cells. The consequences of prenatal irradiation (150 rad) were evident in the 13 week-old mouse. This was manifested by a reduced spleen cellularity and perturbations in concentrations of hemopoietic progenitor cells in the bone marrow.