Kinetic studies of radiation damage and recovery of murine haemopoietic stem cells during and after continuous irradiation at low dose rate.

Abstract

Under continuous gamma irradiation at a low dose rate of 0.70 Gy/day, the cellularities of blood forming cells in bone marrow decrease with increasing accumulated radiation dose. The biphasic nature of the dose-response curve may be due to the following factors: an increased rate of proliferation of CFUs, different radiation sensitivities of CFUs, GM-CFC and E-CFC, an increase in the amplification potential of progenitor cells and proliferative haemopoietic cells, and a reduction in differentiation 'pressure' on CFUs. After 49 days of chronic irradiation the content of E-CFC in murine bone marrow recovers rapidly, and approaches the pre-irradiation level by 5 days. However, the number of CFUs and GM-CFC reaches a plateau value of only 40% of normal within 34 days.