Study of murin hematopoietic progenitor cells response to gamma-neutron mixed radiation of different gamma/neutron ratios

Sentivity of murin CFU-C progenitor cells was detennined in-vivo for mixed radiations fields composed of variable gamma-rays and neutron components. Five tau ratios (D-gamma/D-total) were obtained (from 0.95 to 0.09). CFU-C radiosensitivity were increased with the lower tau values (excess of neutrons). The Biological Effectiveness D-0 value varied from 3.3 +/- 0.22 to 0.85 +/- 0.04 Gy with the decrease of tau. The obtained Relative Biologic Efficiency (RBE) varied from 1.2 +/- 0.08 to 4.7 +/- 0.24. The relation between RBE and tau does not seem to be linear. A study of the radiation components combining effects showed an infra-additivity of the action of the gamma and the neutron comportent delivered simultaneously. These results indicate that variations of the quality of the mixed field in the haemopoietic local territory have great importance in tenns of lethality and damages and, accordingly, in terms of haemopoietic restoration ability.