Discussion 35 



Maybe someone can furnish data which will be more convincing on 

 whether the electrolyte transfers are equally rapid and reproducible. 



Davson: I think the electrolyte transfer is very likely to be much 

 slower and to hold up the whole process. The water transfer is very 

 rapid in every cell, so I would say that what happens first is the move- 

 ment of the electrolyte and the movement of water would not require 

 much time. The evidence I am citing is largely based on work from Prof. 

 Conway's laboratory. 



Hingerty : One of the main experimental difficulties, of course, is in 

 maintaining the normal condition of the cells. When you remove tissues 

 from an animal there is a very rapid increase in molecular concentration 

 in the cells due to breakdown of molecules such as glycogen, hexose esters, 

 phosphocreatine and adenosine triphosphate (Conway, E. J., Geoghegan, 

 H., and McCormack, J. (1955). J. Physiol., 130, -427). If you remove the 

 tissue directly into liquid oxygen, grind to a frozen powder and then take 

 a series of freezing point depressions on this frozen tissue maintained at 0°, 

 extrapolation back to zero time gives a value equal to that obtained for 

 the plasma (Conway, E. J., and McCormack, J. (195S). J. Physiol., 120, 1). 

 This certainly held for liver, kidney and muscle tissue of the rat and it 

 would be interesting to see these techniques applied to other tissues. 



The swelling of the cells in anoxic conditions cannot be due to a failure 

 to pump out water, since the freezing point depressions of respiring and 

 non-respiring kidney slices are the same, and the effect of anoxia may be 

 interpreted as being due rather to cessation of the sodium pump. Break- 

 down of molecules may be partly responsible for the swelling but the main 

 effect appears to be caused by sodium and chloride entering the cell (some 

 potassium leaving), and water then entering to preserve osmotic balance 

 (Conway, E. J., and Geoghegan, H. (1955). J. Physiol., 130, 438). 



