Effect of Low‐dose Irradiation on Pregnant Mouse Haemopoiesis

The effects of low-dose gamma radiation to haemopoietic progenitor cell compartments of the marrow and spleen of virgin female mice and pregnant mice were studied. Microplasma clot cultures were used to asses burst-forming unit-erythroid (BFU-E) and colony-forming unit-erythroid (CFU-E) activity, and double-layer agar cultures were established to evaluate granulocyte-macrophage colony-forming cell (GM-CFC) and macrophage colony-forming cell (M-CFC). The apparent shift in maternal erythropoiesis from the bone marrow to the enlarged spleen was reflected by an increase in the numbers of CFU-E and BFU-E per spleen and a concomitant decrease in CFU-E and BFU-E per femur. Whereas maternal GM-CFC values per femur increased 36%, maternal GM-CFC per spleen increased by 172% compared to virgin values. There was a greater decrease in M-CFC per spleen than per femur in the pregnant animal when values were compared to the virgin animal. Total-body irradiation to the day-10.5 pregnant mouse caused a further suppression of day-14.5 medullary erythropoiesis (i.e. decreased CFU-E values) compared to the response of the virgin female mouse. An ability of the maternal spleen to support further compensatory erythropoiesis following increasing doses of radiation was demonstrated. 4 d after 1.0 Gy exposure, maternal values for GM-CFC per femur or spleen decreased to nonirradiated virgin mice values. M-CFC per maternal femur decreased following 1.5 Gy, but M-CFC per spleen appeared to be unaffected with doses from 0.5 to 2.0 Gy.