Flow cytometric analysis of reticulocyte maturation after erythropoietin administration in rats.

We have proposed a technique for transforming reticulocyte (RET) flow cytometry count into the age distribution allowing for a quantitative characterization of RETs dynamics. This technique was evaluated in homeostatic and erythropoietically stimulated rats. We administered a single intravenous dose (4,050 IU/kg) of recombinant human erythropoietin to Wistar rats, then stained their RETs with thiazole orange, and measured the distribution of the fluorescent signal using flow cytometry. The RET age distribution was determined assuming an exponential decline of RET RNA. The RET distribution over time was characterized by median age, production rate of mature red blood cell in the blood, bone marrow and blood maturation times, and RET loss from the blood. Erythropoietin was found to cause complex changes not only in RET count but also in age distribution. Generally, an increase in RET count was accompanied by the presence of young RETs and a decrease with the presence of old RETs. The rate at which RETs were removed from the blood was affected considerably by erythropoietin administration, and their death was attributed to it. Flow cytometric analysis of RET age distribution expands our understanding of erythropoiesis and augments the information we can obtain from RET measurements. 2009 International Society for Advancement of Cytometry.