Effect of Hypoxia on Erythroblasts from Avian Fetal Liver: Adenosine Triphosphate Levels and Hemoglobin Synthesis

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Abstract
Extract: A system for the isolation and functional evaluation of fetal liver erythroblasts is described. Isolated erythroblasts were pre-pared from 14-day embryonic avian livers and incubated at various oxygen tensions (0, 5, 12, and 95%). The concentration of ATP in erythroblasts remained constant for at least 4 hr at 37°, but was rapidly reduced by incubation in nitrogen. Protein synthesis as measured by L-[14C]leucine incorporation into cell protein occurred at a linear rate in 5%, 12%, and 95% oxygen, whereas little protein synthesis occurred at 0% oxygen. The effect of hypoxia on the type of hemoglobin synthesized was studied in this system by isolating the hemoglobin A, hemoglobin D, and hemoglobin H fractions and determining the incorporation of L-[14C]leucine. The major fraction, hemoglobin A, contained most of the radioactivity; smaller amounts were present in hemoglobin D and hemoglobin H, respectively. The relative proportion of each hemoglobin synthesized was not altered by oxygen from 5% to 95%. These results argue against a direct effect of oxygen on the type of hemoglobin synthesized at this stage of development. Speculation: Early in fetal development nonerythropoietin mechanisms for the regulation of erythropoiesis may exist. The hypoxic stimulus to erythropoiesis is mediated through erythropoietin in definitive erythroblasts, but may have a direct effect in primitive erythroblasts.