Adult Hemoglobins Are Synthesized in Murine Fetal Hepatic

D URING NORMAL MURINE embryogenesis, erythropoiesis first occurs in the yolk sac blood islands, beginning on days 7-8 of gestation.’ These nucleated erythrocytes primarily synthesize embryonic hemoglobins El (x2y2), Eli (a2y2), and Elil (a2z,).2 5 By day I I of gestation, the fetal liven becomes the major site of red blood cell production, which persists until near birth.6 It has been generally accepted that munine fetal hepatic enythroblasts synthesize and contam only adult major (a2 m J0r) and minor (a2 ’ ) hemoglobins.2 Recently, it was found that the circulating primitive nucleated erythrocytes derived from the yolk sac blood islands produce some adult hemoglobins in addition to embryonic hemoglobins.78 Therefore, it should be of interest to determine if fetal hepatic erythropoietic cells can synthesize embryonic hemoglobins as well as adult hemoglobins. In this investigation, hemoglobins present in fetal hepatic erythroblasts were examined by both biochemical and immunocytologic techniques. Moreover, hemoglobins produced in erythroid colonies in vitro, derived from fetal hepatic hemopoietic progenitor cells, were studied. In all instances, adult hemoglobins were detected.