The effects of erythropoietin on haem synthesis in mouse yolk sac and cultured foetal liver cells

ABSTRACT Erythropoiesis in the foetal mouse is reported to occur initially in the yolk sac, followed by the liver, the spleen and finally the bone marrow (Snell, 1956; Borghese, 1959). At 12 days of gestation 97 % of the circulating erythrocytes are nucleated (Craig & Russell, 1964) and presumably arise from the yolk sac blood islands. The cells of this generation persist in decreasing numbers until the 16th day of gestation. Haemoglobin can first be recognized by histochemical methods (O’Brien, 1961) in the yolk sac before somite formation at the early head fold stage and a network of blood islands, almost covering the embryo, rapidly develops (Plate 1, figs. A–F)’