200 M. J. Karvonen 



Recently it has been claimed that other methods for study- 

 ing young or old erythrocytes might be feasible. According 

 to Borun, Figueroa and Perry (1957), after centrifugation of 

 blood the bottom layer contains the oldest cells, and the 

 surface the youngest ones. An analysis of the different layers 

 has shown that — at least in human adult blood — the packing 

 is closest and the amount of intercellular plasma lowest in the 

 bottom layer, but when the effect of different packing is 

 corrected there is no difference between the sodium and 

 potassium concentrations of the bottom and the surface 

 erythrocytes (Leppanen, personal communication). Serial 

 osmotic haemolysis has also been suggested as a means for 

 differentiating young and old erythrocytes (Simon and 

 Topper, 1957). The value of these methods is not yet clear. 

 However, the nature of the methods used suggests that 

 changes in the electrolyte metabolism of the erythrocytes 

 may be involved in their ageing, though such changes may not 

 necessarily result in differences in the concentration of sodium 

 and potassium. 



Age of the animal 



As a mixed population of different cellular ages, erythro- 

 cytes are easily available. The availability and development 

 of flame photometric analysis have been a stimulus for several 

 investigations of the electrolyte content of the red cells. It 

 has been found that in general the sodium and potassium 

 content of the erythrocytes in vivo is fairly stable, typical of 

 the species, and resistant to many physiological and pharmaco- 

 logical agents. However, in disease, particularly in febrile 

 states, erythrocytes tend to lose potassium and gain sodium: 

 in other words, the electrolyte composition of the erythro- 

 cytes moves closer to that of plasma. 



Sheep and other ruminants. It may be inferred from results 

 published by Green and Macaskill (1928), and by Wise and 

 co-workers (1947) that the intracellular potassium concen- 

 tration is higher in the blood of young calves than in that of 

 adult cattle. These two papers were the first to indicate that 



