Steroids and hematopoiesis. III. The response of granulocytic and erythroid colony-forming cells to steroids of different classes.

Selected androgenic and nonandrogenic steroids enhance in vitro granulocytic and erythroid colony formation by mouse marrow cells, but do so by influencing either different target cells or cells in different states of cell cycle. Etiocholanolone, a naturally occurring nonandrogenic testosterone metabolite, permits cells not in active cycle to respond to colony-stimulating factor or erythropoietin. Fluoxymesterone, a synthetic androgen, appears to enhance colony growth by increasing the responsiveness of target cells to tropic stimuli. The majority of cells responding to this androgen are in active DNA synthesis. Direct comparison, however, of etiocholanolone-dependent erythroid or granulocytic colony-forming cells demonstrates nonidentity of the target cells. Thus colony-forming units responding to different classes of steroids are in different states of cell cycle and are physically separable. The enhancement of the in vitro response of colony-forming cells to regulating hormones by steroids such as etiocholanolane suggests a mechanism by which such agents may be therapeutically effective in certain cases of marrow failure in man.