Dehydration of Transferrin Receptor -Positive Sickle Reticulocytes During Continuous or Cyclic Deoxygenation: Role

The K+ efflux that mediates sickle-cell dehydration may occur through several pathways, including two with a high capacity for mediating rapid K+ loss, KCI cotransport and the Ca2+-dependent K’ channel [K(CaZ+)I. The rate and pathway of red blood cell (RBC) dehydration most likely depends on cell age and hemoglobin (Hb) composition, with the presence of HbF playing an important role. Oxygenated sickle RBCs have relatively stable cell volume during incubation in vitro, whereas deoxygenated cells become dehydrated, and therefore more dense, due to activation of one or more K+ efflux pathways. In this investigation, sickle RBCs were deoxygenated either continuously or in 15-minute cycles for 4 hours, and the density increases of very young, transferrin receptor-positive (TfR+) cells and the remaining TfRcells were determined. The contribution of KCI cotransport was