Fusion of human erythrocyte ghosts promoted by the combined action of calcium and phosphate ions

CALCIUM ions are important in almost all membrane fusion systems ^1-2. Murayama and Okada³ showed that Sendai virus-induced fusion of Ehrlich ascites cells required Ca²⁺. When Ehrlich ascites cells were treated with Sendai virus in the presence of EDTA, cells agglutinated and lysed but did not fuse^3,4. Similarly, Ca²⁺ was required for the fusion of erythrocytes stimulated by chemicals such as lysolecithin⁵ or glyceryl monooleate⁶. Ca²⁺ plus the ionosphere A23187 (ref. 7) or Ca²⁺ at high pH (ref. 8) promoted the fusion of chicken erythrocytes. Fusion of phosphatidylserine-rich liposomes was absolutely dependent on the presence of Ca²⁺⁹. We describe here the fusion of human erythrocyte ghosts promoted by the combined action of Ca²⁺ and phosphate buffer. Human erythrocyte ghosts, because they lack cytoplasm and are easily filled with small or large molecules^10,11 are useful for the investigation of membrane fusion.