Differential Split-dose Radiation Response of Resting and Regenerating Haemopoietic Stem Cells

Abstract

Haemopoietic stem cells are less sensitive to killing by a dose of radiation, if it is delivered in two fractions separated in time. The magnitude of this decrease in sensitivity is greater when the cells are irradiated in the normal steady state, compared with a regenerating state. However, the effect was reversed when donor mice received two radiation doses, separated in time by 24 hours, and this was due to effects (on differentiation and on proliferation) occuring between the first and second doses. These observations are discussed in relation to the therapeutic practice of daily dose treatments.