Figure 4.

Effect of manipulation of intracellular Ca²⁺ on phosphatidylserine (PS) exposure in red blood cells (RBCs) from sickle cell patients. RBCs were first treated with vanadate (1 mM) to inhibit the plasma membrane Ca²⁺ pump and also the aminophospholipid translocase (flippase) before addition of bromo-A23187 (1.2 μM, 1% haematocrit) and requisite extracellular [Ca²⁺]s for 30 min. They were then treated with Co²⁺ (0.4 mM) before labelling with FITC-annexin. Intracellular [Ca²⁺] is calculated from extracellular [Ca²⁺] × r ², where r ² was taken as 2.05 [36]. Results presented are from a single experiment representative of 5 others.