Structural and dynamic aspects of the red cell membrane 1

Abstract

Treatment of intact fresh human red cells with phosphate and calcium ions, in that order, led to cell agglutination at room temperature, and hemolysis and fusion at 37°C within 30–60 minutes. During incubation, cell-associated calcium increased 70 fold, while ATP levels declined by 98%. Agglutination was much reduced after neuraminidase treatment, suggesting that surface negative charges play a role in phosphate-calcium bridging between cells. Incorporation of 10 mM EGTA into resealed ghosts increased the fusion index relative to control ghosts while the incorporation of 1 mM calcium had the opposite effect. Aggregation of membrane-associated proteins was demonstrated by freeze-fracture and by glycoprotein labeling.

In summary, phosphate and calcium ions cause agglutination of red cells and an increased permeability to cations resulting in hemolysis, an aggregation of membrane proteins and finally fusion of adjacent protein-free lipid bilayers.