It was confirmed that the lysolecithin contents of human erythrocyte membranes (stroma) can be varied remarkably depending on the plasma lysolecithin concentration in vitro and that simultaneously certain changes occur in the morphology of the whole cell as revealed by scanning electron microscopy, and also in the osmotic fragility of the membranes.
Incubation of erythrocytes in lysolecithin-rich plasma, prepared by the action of the plasma lecithin-cholesterol acyltransferase or of added phospholipase A of snake venom, resulted in remarkable increase in the lysolecithin content of the erythrocyte membranes and morphological changes in the erythrocytes from normal biconcave discs to crenated or spherical forms. The spherical cells, but not the crenated cells, showed increased osmotic fragility. After washing these lysolecithin-rich erythrocytes with serum albumin solution or with heated normal plasma, the erythrocyte lysolecithin content was restored almost to the normal level whereas the increased osmotic fragility still persisted.
Similar washes of the normal erythrocytes with albumin solution gave rise to about 43% decrease in the lysolecithin content, slight morphological change and also slight increase in the osmotic fragility. When these cells were incubated in heated normal plasma, the lysolecithin content was restored to the normal level, and at the same time both the slightly-altered shape and osmotic fragility were restored back to normal.
From these experimental findings, probable existence of two kinds of lysolecithin pools in human erythrocyte membranes and their roles in the maintenance of the membrane structure and functions were discussed.