206 Discussion 



DISCUSSION 



Davson : The most interesting thing here is the finding that these red 

 cells have a very high sodium concentration and alow potassium one. One 

 thinks of it at first as a primitive feature. On the other hand, when one 

 looks through the animal species in which it happens, it is most promi- 

 nent in the cat and dog, whilst the guinea pig, which we think of as a 

 rather primitive animal, has a very high potassium just like man. So it 

 has nothing to do with that. Then you also think of it as a failure to 

 develop a potassium-accumulation mechanism. There again, it is prob- 

 ably not to be considered as a failure at all. The red cell is derived from 

 a very highly developed nucleated cell and most likely the erythroblast 

 has the ability to concentrate potassium. Then when the cell becomes a 

 reticulocyte or an erythrocyte it loses the power of accumulation of 

 potassium. This 'loss' could be a development in the interests of eco- 

 nomy, because much less energy is required to maintain a cell with a low 

 concentration of potassium than with a high one, and the erythrocyte 

 has only an anaerobic source of metabolism. 



Your results with the foetal cells are interesting, Dr. Karvonen. With 

 sheep, you find that the foetal erythrocytes have the high potassium and 

 it looks as if as they develop they lose the power of accumulating potas- 

 sium. But then, with the other species, we get the reverse. I think a lot 

 more work on the spontaneous haemolysis is necessary. Haemolysis 

 usually has a very definite cause and is usually due to the fact that the 

 permeability of the membrane becomes abnormally high and you get 

 this Donnan difference of osmotic pressure being exerted between the 

 plasma and the contents of the cell. Therefore, the most profitable line 

 of research would be to try and get conditions in which you could prevent 

 this haemolysis from occurring. 



Milne : Is there any data available on the foetal levels in the cat and 

 the dog, which have this very high sodium content in the erythrocytes? 



Karvonen: No, we have none. 



Davson : The sheep can have as high a sodium content as the cat, yet 

 there is very little difference between foetal sheep. Would it be possible 

 to get a nucleated stage in the erythrocyte of the mammal and study its 

 potassium content? It could almost be done histochemically, just to get 

 a qualitative idea of the content. 



Karvonen: That would be a very interesting thing to do. 



Fourman : Tosteson reported a low erythrocyte potassium in sickle-cell 

 anaemia (1953. J. din. Invest., 32, 608). That confirms your view that 

 the level of potassium in the blood may be related to abnormal haemo- 

 globins ; is there any information on that, outside man? 



Karvonen: In sheep, the type of haemoglobin affects the absolute 

 level of electrolytes within the same group. If you have sheep with low 

 potassium-containing red cells, and one of the animals has a different 

 type of haemoglobin, the electrolyte level in its red cells is also slightly 

 different. 



Desaulles: Has not the same effect been described for some kind of 



