Water distribution in blood during sickling of erythrocytes.

Plasma urea and protein determinations proved suitable for measuring changes in total diffusible water and plasma volume in whole blood. Deoxygenation by saturation with carbon dioxide at 25 degrees C caused no change in plasma urea, but a significant increase in plasma protein concentration was induced with both normal and sickle-cell (HbSS) blood. Thus in HbSS blood there was no binding or trapping of water as a result of sickling and there was a normal influx of water into the cells (Bohr effect) despite the polymerization of the hemoglobin molecules with sickling. Consistent with this observation was the finding that the deoxygenation induced a similar increase in concentration of the plasma cations, sodium plus potassium. HbSS erythrocytes neither lost nor gained water under the more physiologic conditions of deoxygenation with a 95% nitrogen, 5% carbon dioxide gas mixture.