Effect of hydrocortisone on radiosensitivity of hemopoietic stem cells

Differentiation and radiosensitivity of colony-forming units (CFU) of the bone marrow and spleen were studied in the course of one month after a single injection of hydrocortisone to mice (5 mg/mouse). The direction of differentiation of CFU from different organs was found to change drastically. CFU of the bone marrow stimulated erythropoiesis and of spleen, myelopoiesis which is different from what we have in normal mice. Study of the radiosensitivity of CFU from various organs by the ''splenic colony'' test did not show any variations in the values of D0 and the extrapolation number, whereas the ''bone marrow colony'' test exhibited considerable atleration of the CFU radiosensitivity. Radioresistance of CFU from bone marrow decreased while that of splenic CFU increased compared with controls. The phenomena described are probably due to redistribution of T-lymphocytes in response to the hydrocortisone administration