58 



ELECTROLYTES IN BIOLOGICAL SYSTEMS 



enough to account for the observed ratio of internal to external potassium and 

 the Donnan principle cannot apply (28). 



Influence of Cold on Ulva and Valonia. One of the first suggestions that there 

 was a close association of metabolism with cation regulation was made by 

 Harris (16) on observing a reaccumulation of potassium by human erythrocytes 

 after the cells had been kept in the cold and were then returned to 38°C. A 

 study of the Qio for potassium exchange by Ponder (31), Sheppard and Martin 

 (41) and Raker et al. (32) further supported the idea of a direct influence of 

 carbohydrate metabolism on electrolyte balance. 



TRANSFERRED 



TO 



RUNNING SEA WATER 



50 100 150 200 250 300 350 400 



HOURS 



Fig. 17. Loss of potassium and gain of sodium in Valonia macro pliysa resulting from o.ooi 

 m/1. phenyl urethane. At the time indicated by the arrow the cells were transferred to running 

 sea water without the inhibitor. 



Attempts to demonstrate an influence of temperature on sodium and potas- 

 sium balance in Ulva have not been too successful since these cations in Ulva 

 undergo no significant change when the alga is maintained at 2°C for 24 hours. 

 It is possible that mechanisms operate to reduce the permeability of the cells 

 to cations so that even though the rate of metabolism (and likewise transport 

 mechanisms) is reduced, the cell maintains its normal composition at least for 

 24 hours. 



In the case of Valonia, however, when the cells are maintained at 2 to 5°C 

 for approximately 75 hours, a slight loss of potassium and gain of sodium occurs. 

 On return to a temperature of i8°C a further and striking loss of potassium and 

 gain of sodium takes place. After 75 hours at the higher temperature a reac- 

 cumulation of potassium and a secretion of sodium begin and continue for 

 about 250 hours. Within this time the cells have restored nearly the normal 

 potassium and sodium levels (fig. 18). 



