Mechanisms of Action of Testosterone on Hemopoiesis in vivo and in Diffusion Chambers

Summary Injection of long-acting testosterone markedly enhanced bone marrow CFU-S proliferation in vivo and CFU-S recovery in a diffusion chamber (DC) system. In the DC system the enhanced CFU-S proliferation led to increased cellularity due to an increase in dividing granulocytic elements and macrophages. In vivo, no difference was observed in the tibial total nucleated cellularity between treated and control animals. Detailed marrow differential counts, however, showed a significant increase in erythroid cell precursors 1-3 days after testosterone injection. The relationship between colony-forming units and colony-forming cells is discussed and it is suggested that testosterone may act on different levels of the hemopoietic system. This steroid appears not only to enhance but also to induce proliferation of the uncommitted progenitor cells.