Calcium-induced Damage of Haemoglobin SS and Normal Erythrocytes

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Abstract
An ionophore specific for divalent cations was used to load normal erythrocytes and erythrocytes from patients with sickle cell anemia (Hb SS disease) with small amounts of Ca. Such Ca accumulation leads to decreased cellular water, K, ATP and osmotic fragility, all characteristics of irreversibly sickled cells (ISCs). Ca loading of Hb SS, but not normal, erythrocytes causes a marked decrease of Hb oxygen affinity; another, and specific, hallmark of ISCs. Ionophore-induced accumulation of Ca by deoxygenated Hb SS erythrocytes also leads to temporary retention of sickled shape following reoxygenation, despite the absence of detectable intracellular Hb SS fibers. All these effects require Ca in the incubation medium. Increased intracellular Ca is apparently important in the formation of ISCs in patients with Hb SS disease.