Erythropoietin Effects on Fetal Mouse Erythroid Cells

Abstract

The effect of the hormone, erythropoietin, on cultures of erythroblasts derived from the livers of fetal C57BL/6J mice was examined . An increase both in the content and in the rate of synthesis of normal adult mouse globin chains was detected in hormone-treated cultures . The rate of protein synthesis by individual erythroblasts does not increase in response to the hormone, whereas the absolute number of hemoglobin-synthesizing cells does increase and accounts for the observed stimulation of hemoglobin synthesis . The principal effect of erythropoietin appears to be upon the population of immature erythroid precursor cells which persists in the presence of the hormone, the cells maintaining their ability to replicate, and their capacity to differentiate into hemoglobinizing erythroblasts . In the absence of hormone, already committed erythroblasts continue their development, but erythropoiesis is not sustained .

Purification of Erythropoietin-Responsive Cells by Immune Hemolysis

“…The present impure state of erythropoietin does not permit us to dismiss the possible effects on the culture of contaminants in the preparation. Nevertheless, the present observations, taken together with previous studies (2,3,12), strongly suggest that the primary effect of the hormone in vitro is expressed as accelerated RNA synthesis by precursor cells, followed by cell division and the initiation of hemoglobin synthesis. Effects of erythropoietin on the viability and rate of maturation of differentiating erythroblasts were not specifically tested in these studies and, thus, cannot be definitely excluded.…”

“…In the absence of erythropoietin, immature precursors are neither triggered to replicate nor to differentiate into hemoglobinizing progeny. As a consequence, the population rapidly decreases and erythropoiesis is not sustained (2,3). The present impure state of erythropoietin does not permit us to dismiss the possible effects on the culture of contaminants in the preparation.…”

“…Timed pregnancies were obtained in hormonally primed C57BL/6J female mice (7); fetal hepatic hemopoietic cells were obtained from 12-or 13-day embryos by mechanical disaggregation of the dissected livers (3). Cells were collected in ice-cold Waymouth MB752/1 medium (GIBCO Grand Island, N.Y.), supplemented with 10% fetal-calf serum (Microbiological Associates, Bethesda, Md.…”

“…Elucidation of the cellular and molecular effects of erythropoietin has been aided by the development of several in vitro systems, including the short-term culture of bone marrow (1) and fetal hepatic erythroid cells (2,3). However, interpretation of these studies is hindered by the presence of large numbers of differentiated hemoglobin-synthesizing cells in the culture.…”

Proliferative capacity of mouse peritoneal macrophages in vitro.

“…Removal of the stimulus causes these cells to return to a nonproliferative "resting" state; a state that can be entirely reversed by the readdition of the stimulus. Other hemopoietic cells seem to be similarly regulated: for example, the formation of granulocyte and macrophage colonies by bone marrow cells in the presence of colony stimulating factor (10), and the differentiation and division of erythroid cells to hemoglobin-producing cells by erythropeietin (28). Also the lymphocyte proliferative response requires the continuous presence of mitogens (29,30).…”