Effects of abnormal cation transport on deformability of desiccytes.

We have studied the deformability of subpopulations of red cells from a patient with "desiccytosis," a disorder characterized by increased membrane permeability to potassium and associated with a probable increase in sodium-sodium exchange. Cells become increasingly dehydrated after maturation because of continued potassium loss without compensatory sodium gain, and they exhibit a progressive increase in mean cell hemoglobin concentration (MCHC). This increase in MCHC causes the cells to become underformable at shear stress values which result in extensive deformation of normal cells. Reduction of MCHC to approximately normal levels by suspending the cells in hypotonic medium restores normal deformability to all but 0.1--0.2% of the cells. These results suggest that the major factor leading to premature destruction in this disorder is whole cell rigidity conferred by increased intracellular hemoglobin concentrations, rather than any associated membrane rigidity.