The effect of hydrocortisone on the production and differentiation of granulocyte/macrophage progenitor cells in long-term bone marrow cultures.

In long-term murine (BDF1) marrow cultures with a 'sufficient' lot of horse serum, hydrocortisone (HC) treatment (10(-6) M) had no apparent effect on the production of granulocyte/macrophage precursor cells (CFUc) in suspension. There was, however, a remarkable increase in granulopoiesis with a corresponding decrease in monocyte-macrophage production; the mean ratio of total granulocyte to monocyte-macrophage was approximately 6.0 during HC treatment, while it was approximately 1.0 in control cultures. Although there was no biodetectable colony-stimulating activity in the cultures, colony-enhancing activity was demonstrated without differences in the activity and specificity on colony formation between cultures with and without HC supplement. Moreover cells harvested from the cultures with HC gave rise to a significantly higher incidence of granulocyte colonies and so did the freshly isolated bone marrow cells in the presence of HC in agar culture system. This effect of HC on CFUc differentiation was not affected by indomethacin treatment.