Red blood cell (RBC) volume can be independently determined in vivo in the sheep using ovine RBCs labeled at different densities of biotin

Abstract

BACKGROUND-To investigate the pathophysiology of anemia and responses to RBC transfusions and erythropoietin, repeated measurement of the circulating red cell volume (RCV) would be useful. Ovine erythropoiesis is similar to human erythropoiesis. Accordingly, a method for measuring RCV using either human or sheep RBCs labeled at different biotin densities has been previously validated in vitro. Here preclinical studies validating this method for in vivo measurement of circulating RCV in sheep are reported.

Post‐transfusion survival of biotin‐labeled allogeneicRBCs in adult horses

“…This may be secondary to transient pooling or sequestration of labeled cells immediately following reinfusion, which would actually result in underestimation of initial biotinylation as measured at time 0 and subsequent overestimatation of biotinylation at 24 hours. Using biotinylated RBCs to estimate blood volume in sheep, a similar result was observed with a slowly equilibrating pool of biotinylated RBCs in these sheep . Biotinylated RBCs were hypothesized to have been sequestered in the spleen or other organs of the monocyte‐macrophage phagocytic system.…”

“…Using biotinylated RBCs to estimate blood volume in sheep, a similar result was observed with a slowly equilibrating pool of biotinylated RBCs in these sheep. 28 Biotinylated RBCs were hypothesized to have been sequestered in the spleen or other organs of the monocyte-macrophage phagocytic system.…”

Red blood cell (RBC) volume can be independently determined in vivo in humans using RBCs labeled at different densities of biotin

“…To further enhance the utility of the biotin method, we refined the technique for biotin labeling to produce four separate populations of RBCs with increasing biotin density per RBC and validated the use of these RBCs to independently and simultaneously measure RCV in vitro and in vivo both in sheep 22 and human adults. Because the densities are independently enumerated and do not overlap in the histogram (see Fig.…”

“…The method utilizing biotinylated RBCs does not expose the subject to radiation and has been validated against 51 Cr-labeled RBCs (the established standard method) in animal and humans studies using RBCs labeled at a single density of biotin. [8][9][10]12,17,21 To further enhance the utility of the biotin method, we refined the technique for biotin labeling to produce four separate populations of RBCs with increasing biotin density per RBC and validated the use of these RBCs to independently and simultaneously measure RCV in vitro and in vivo both in sheep 22 and human adults. Because the densities are independently enumerated and do not overlap in the histogram (see Fig.…”

In premature infants there is no decrease in 24‐hour posttransfusion allogeneic red blood cell recovery after 42 days of storage

“…For each sample, 1 × 10 6 RBCs were counted . For the rare samples exhibiting overlap in the fluorescence histogram between the BioRBC peaks or between the unlabeled RBCs and the lowest biotin density, mixed modeling was used to calculate the proportion of RBCs in each population as previously described . The lower limit of quantitation for individual BioRBC density peaks is 0.06% of total RBCs …”