[The effect of growth hormone on leukopoiesis: in vivo and in vitro studies].

Growth hormone (GH), which has been extracted from the pituitary gland since early times, has become easily available by the advance of genetic engineering in recent year. Its clinical application to treatment in various fields, involving obesity, wounds, fractures, gastric ulcers and so on, is being increasingly discussed. The presence or absence of the effect of GH on leukopoiesis was studied in vivo and in vitro experiments. In the in vivo experiment, GH was administered to rats whose bone marrow production had been suppressed by the injection of mitomycin C, and time-course changes in the peripheral blood leukocyte count in these rats were compared with those in rats given physiological saline solution alone (control group). The in vitro experiment was performed by colony assay of mouse marrow cells. Insulin growth factor-1 (IGF-1) was also studied in the in vitro experiment. The in vivo experiment revealed that GH promoted recovery of leukocytes from the nadir, and in the in vitro experiments GH and IGF-1 were demonstrated to increase the number of colonies in the presence of granulocyte macrophage colony stimulating factor (GM-CSF). GH was considered to exert effects on myeloid progenitor cells and the hemopoietic microenvironment simultaneously, resulting in an increase in leukocytes.