Amino acid accumulation by human reticulocytes.

ETICULOCYTES of several species have been shown to accumulate amino acids, and incorporate them into hemoglobin.12 While the ratio of the concentration of certain amino acids in mature human red cells to the plasma concentrations of the same amino acids has been studied,1 there has been no study of this ratio in human reticulocytes. Because of the presence of large amounts of fetal hemoglobin in the red cells of patients with thalassemia major, this inherited congenital anemia has been considered to be due to defective adult hemoglobin synthesis.” The present investigation explores the possibility that this defective adult hemoglobin synthesis and the production of fetal hemoglobin is associated with an abnormality of amino acid accumulation by the thalassemic red cells. Since fetal and adult hemoglobin differ in isoleucine, valine, and histidine content,7’8 these amino acids were measured specifically, as well as certain other amino acids. The ratio of intracellular to extracellular amino acid concentration was used as an expression of the ability of red cells to accumulate amino acids. This ratio was determined in blood samples from normal adults which contain few reticulocytes and therefore do not synthesize appreciable hemoglobin, in samples from patients with hemolytic anemia with large numbers of reticulocytes, which synthesize normal adult hemoglobin,9 and from neonatal’41 and thalassemic blood capable of synthesizing both fetal and adult hemoglobin.