[Mechanism of radioresistance of the hematopoietic system after treatment with diethylstilbestrol].

The effect of diethylstilbestrol on the hematopoietic system of intact animals and on dynamics of post-radiation hematopoiesis recovery was studied. The injection of diethylstilbestrol into unirradiated animals was shown to induce the decrease in CFUs and CFU-GM content in bone marrow, the increase in granulocyte-macrophage precursors number in spleen, the decrease in proliferative activity of hematopoietic precursor cells and the rise of CSF-GM levels in the sera at the period of optimal manifestation of radioprotective effect. Mice, which were protected by diethylstilbestrol, demonstrated much more powerful recovery of CFUs, CFU-GM numbers as well as myeloid and erythroid hematopoiesis series in comparison with irradiated control animals. It seems that radioprotective action of diethylstilbestrol is provided by the initial decrease of amount of early hematopoietic precursor cells as a result of suppression of their proliferative activity that causes the increase of endogenous growth and differentiation factors levels, which induce the changes in proliferation and differentiation of hematopoietic stem cells, providing the intensification of post-radiation hematopoiesis recovery.