Age Changes in Red Blood Cells 203 



influence on the concentration of potassium in the whole 

 blood of both high potassium and low potassium sheep, and 

 thus presumably also on the concentration of potassium in the 

 cells themselves (Evans et ah, 1956). 



The study of individual differences between adult sheep thus 

 shows that the type of haemoglobin is associated with the red 

 cell electrolytes, but that other factors also play a role. 



Haemoglobin changes with age: the haemoglobin of a foetus 

 differs from that of an adult, but after the production of the 

 adult type is once established, no further changes with age are 

 known to occur. For instance, the haemoglobin of a sheep of 

 the age of 14 years showed solubility characteristics identical 

 with that of younger animals (Karvonen, unpublished.) 



The transition from foetal to adult life involves a change of 

 haemoglobin and of the red cell electrolytes. In sheep, these 

 two changes appear to start before delivery and to be com- 

 pleted some time after birth (Karvonen, 1949; Hallman and 

 Karvonen, 1949; Widdas, 1954). Whether the changes are 

 exactly parallel would be a subject of considerable theoretical 

 interest. 



Other species. The effect of age on the electrolyte concen- 

 tration of red cells has been studied in few other species. 

 Remarkably enough, a relationship just opposite to that in 

 ruminants has been found: the sodium concentration is 

 higher and the potassium concentration the same or lower in 

 foetal than in adult erythrocytes, at least in man (Hallman, 

 Osterlund and Vara, 1954; Osterlund, 1955; McCance and 

 Widdowson, 1956), pig (McCance and Widdowson, 1956), and in 

 guinea pig (Widdas, 1954, 1955; Karvonen and Leppanen, 

 unpublished). The concentration of chloride changes in the 

 same direction as that of sodium. 



Underlying mechanisms 



It has been pointed out by Conway (1957) that the smaller 

 a cell, the more work per unit cell volume a "sodium pump" 

 must do in the same environment of plasma or extracellular 

 fluid, in order to keep the intracellular sodium at constant 



