Human Red Cell Instability and Senescence 219 



but depends upon the previous treatment of the cells. It 

 increases with the length of time the cells have been stored in 

 vitro and decreases with the number of times they have been 

 washed. 



The effect of repeated suspensions in 0-16 M-NaCl is shown 

 in Fig. 1. Even after 20 washes only 6 per cent of the cells 

 have haemolysed, and the proportion haemolysing was con- 

 stant for each washing. During the first 7 washes, however, 



10 20 30 40 50 

 TIME (MINUTES) 



60 



Fig. 2. The rate of removal of components from the red 

 cell by exposure to alumina. Cells suspended in 16 

 M-NaCl were exposed to powdered alumina (500 mg. 



A1 2 3 per ml. of packed cells) at 37° 

 Dry weight of lipids ; + Lipoprotein ; 



(J Cholesterol ; X Phospholipid ; O Haemoglobin. 



a considerable amount of the cell membrane was dispersed 

 in the medium and shrinkage of the cells took place. There- 

 after the losses of cell components proceeded at a rate equi- 

 valent to the loss of cells by haemolysis. 



Figs. 2 and 3 show that the effects of exposure to alumina 

 are closely similar to those of repeated washing. The haemo- 

 lysis of the cells is directly related to the time of exposure and 

 concentration of alumina. The loss of lipids, however, bears a 

 direct relationship to the time and intensity of exposure only 



