Human reticulocytes isolated from peripheral blood: maturation time and hemoglobin synthesis

A pure population of young reticulocytes was isolated from the blood of healthy blood donors by an immunomagnetic technique. The young reticulocytes isolated had a larger mean corpuscular volume (MCV) but lower mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) than reticulocytes in peripheral blood. The cells were incubated in vitro for 5 days with hemolysis less than 5%. Maturation of reticulocytes was studied with 4 different systems: new methylene blue-stained smears and flow cytometry after auramine O, oxazine 750, or thiazole orange staining. The maturation process from reticulocytes to erythrocytes had a half-life of 30 hours estimated by visual counting. Reticulocytes analyzed with flow cytometers had half-lives of 20, 28, and 29 hours with Coulter Epics XL, Sysmex R-1000, and Bayer H*3 devices, respectively. Total maturation time was 4 to 5 days. During maturation, the reticulocyte MCV gradually decreased with a concomitant increase in reticulocyte MCHC. The reticulocytes synthesized hemoglobin, and the MCH of the cells increased approximately 7% during the incubation period. Taking into account loss of hemoglobin-containing vesicles during reticulocyte maturation, we estimated that more than 20% of hemoglobin in erythrocytes was synthesized in reticulocytes after release from bone marrow.