Hemolysis of erythrocytes as a model for membrane instability and rupture

Membrane injury of hemolyzing erythrocytes was observed under scanning electron microscopy by a method which enabled fixing of the holes at the moment of their formation. When the cells were lysed at room temperature, the injury consisted of a long, narrow tear dividing the cell in two halves. The rupture was identical in appearance when the cells were caused to lyse at 49.5 °C, in which case the cytoskeleton was denatured and the membrane consisted mainly of the lipid bilayer. If an amphipathic detergent, lysophosphatidylcholine (LPC), was present in the lysing medium, circular holes were formed in the membrane. The results show that lipids control the appearance of the hemolytic hole. The formation of the long tear can be attributed to a wavy instability that arises in the membrane after the connections between the membrane layers are damaged. These layers begin to oscillate so that the distance between them changes periodically. When the oscillation is of a squeezing wave mode, a local thinning develops, leading to a tear in the membrane. The round holes formed in the presence of LPC can be explained by globular micelles formed by the LPC along the edges of the growing hole at the moment of its formation.