The effect of cell hydration on the deformability of normal and sickle erythrocytes

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Abstract
The deformability of the erythrocyte (RBC) is greatly influenced by its state of hydration. This relationship was quantitated by measuring the deformability of an RBC population over a broad range of cell water content. By manipulation of the ion content of the RBC, all of the experiments were performed in media which were isotonic with plasma. To raise ion and water content, RBC were incubated in Li2CO3 medium. To lower cell ion and water content, RBC were exposed to the K ionophore, valinomycin. The range of cell water content achieved during the entire experiment was 900-3200 g/kg cell solid (normal in vivo cell water content being 1800-1950 g/kg cell solid). Deformability of the RBC sampled at various points along this range of cell water content was measured by using the Ektacytometer, an automated cylindrical viscometer. Optimal rheologic behavior was exhibited by normal RBC when their water content was in the normal range. A rise or a fall in cell hydration resulted in a decrease in cell deformability. The deformability of freshly drawn, well-oxygenated sickle RBC was well below that found for normal RBC. Upon volume expansion, the deformability of these sickle RBC improved markedly. Sickle RBC apparently are suboptimally hydrated; their abnormal rheology is partially a consequence of cell dehydration.