Effect of hydrocortisone on BFU-E growth and on burst-promoting activity of T lymphocytes in man

Glucocorticosteroid hormones have been reported either to stimulate or to inhibit human erythropoiesis. We have studied the in vitro effect of hydrocortisone, 10(-6) mol/l, on human BFU-E when stimulated by preconstituted burst-promoting activity (BPA) in a medium conditioned by T lymphocytes. Hydrocortisone was found to stimulate BFU-E growth, even at largely suboptimal concentrations of BPA, through hormone receptors, as the effect was blocked by preincubation of BFU-E with equimolar progesterone. The possibility that glucocorticosteroids may increase the number and/or affinity of erythropoietin receptors on BFU-E is discussed. We have also studied the effect of hydrocortisone on the production of BPA by human T lymphocytes stimulated by phytohemagglutinin. Preincubation of T lymphocytes for 1 h with hydrocortisone, 10(-6) mol/l, significantly reduced the BPA of lymphocyte-conditioned medium. Again the inhibition of BPA production was reversed by incubation of lymphocytes with equimolar doses of progesterone. The conflicting results previously reported on the effect of glucocorticosteroids on erythropoiesis may be due in part to the opposing effects of the hormones on BFU-E growth and BPA production. The role hydrocortisone plays in the physiological regulation of human erythropoiesis is at present largely unknown.