Influence of red cell water content on the morphology of sickling.

The response of sickle cells with varying water content to alterations in oxygen tension has been studied. Cells that were severely dehydrated while sickled retained the characteristic sickled morphology even after prolonged reoxygenation. When the cell water content was increased by reduction of the suspending medium osmolality, the cells unsickled. Cells that were dehydrated before deoxygenation were unable to assume the spiculated morphology typical of sicked cells. This was true both for high mean cell hemoglobin concentration (MCHC) discoid sickle cells and for irreversibly sickled cells. When such cells were resuspended in hypotonic medium before deoxygenation, they sickled with the characteristic morphology of sickle cells with normal MCHC. The morphological behavior of Ca-loaded sickled cells as well as irreversibly sickled cells showed a major influence of increased hemoglobin concentration and extremely high internal viscosity. Constraint on cell morphology by putative membrane rigidity was not observed.