Human Red Cell Instability and Senescence 221 



after a considerable proportion of the membrane has been 

 removed. This proportion appears to be more or less inde- 

 pendent of the concentration of alumina. 



The results suggest that the dissolution takes place in two 

 steps. First, there is a rapid loss of superficial or surplus 

 material which is not immediately harmful. Thereafter the 

 rate of loss of membrane components is closely proportional 

 to the rate of haemolysis. This suggests that any further loss 

 of material from individual cells leads to their rapid and 

 complete destruction. 



Figs. 4 and 5 show the effect of temperature upon the rate 

 of loss of lipids and the haemolysis of cells exposed to alumina. 

 Between 40° and 5° the rate of haemolysis proceeds in a 

 manner consistent with a process governed by simple diffusion, 

 that is, with an activation energy of 5500 calories. Below 

 +5° the rate of haemolysis and loss of lipoprotein begins to 

 increase, but the loss of cholesterol and phospholipid continues 

 to fall. 



Previous experiments (Lovelock, 1954) indicated that the 

 loss of components from the red cell is not reversible in a 

 simple manner. Cells which have been denuded of membrane 

 components regain very little of their lost material after one 

 hour in fresh plasma at 37°. 



The experiments just described were carried out using cells 

 stored at 4° in "acid citrate dextrose" media for from 3 to 

 10 days. During this period of storage there is little or no 

 change in the viability of the cells, as judged by their survival 

 on transfusion (Loutit, Mollison and Young, 1943). It was 

 noted, however, that the deleterious effects of both repeated 

 washing and exposure to alumina increased during this period 

 of storage. 



The experimental evidence shows that a considerable pro- 

 portion of the red cell membrane is easily detached by washing 

 or by exposure to alumina. The proportion detached does not 

 appear to be a defined superficial layer or capsule, since the 

 proportion lost varies with the temperature and duration of 

 cold storage. The removal of this layer is not immediately 



