Change in density score (DS) compared with the percentage of deoxygenation sickling for transferrin receptor-positive and transferrin receptor-negative cells in the presence and absence of extracellular calcium.

The change in DS is defined as the DS after 4 hours of oxygenation/deoxygenation cycling minus the DS of the appropriate control incubated for 4 hours under oxygenation conditions. Open symbols indicate experiments with (○) or without (⋄) calcium. Shaded symbols indicate experiments with (•) or without (▪) chloride in the presence of calcium. Symbols connected by a dotted or broken line indicate paired experiments.