ANALYSIS OF HEMATOPOIESIS IN MICE IRRADIATED WITH 500 MGY OF X-RAYS AT DIFFERENT STAGES OF DEVELOPMENT

We have investigated whether a relatively low dose of 500 mGy of X ray s given as a single acute irradiation at different stages of pre- and postnatal development induces significant changes in the content of fe moral hematopoietic progenitors during a 1-year period after irradiati on. Data obtained show that, in the case of 4-day-old embryos as well as in 2-day, 8-day and 12-week-old mice, this dose is below the thresh old capable of inducing a long-term impairment of hematopoiesis in the mouse. Nevertheless, in mice irradiated at the 13th or the 17th day p ostconception, a hematopoietic dysfunction consisting of a significant reduction in the proportion of femoral granulocyte-macrophage colony- forming units (CFU-GM) was manifested 1 year after irradiation. Our st udy confirms that, for most stages of development in the mouse, a sing le acute X irradiation of 500 mGy is below the threshold dose capable of inducing deterministic effects in the mouse hematopoietic system, a lthough it reveals the induction of a significant impairment in the CF U-GM population when irradiation is given at the late stages of embryo nic development. (C) 1995 by Radiation Research Society