142 



ELECTROLYTES IN" BIOLOGICAL SYSTEMS 



the resistance to cation diffusion. The apparent increase in the rate of cell 

 metabolism when S-S cell are incubated in N2 rather than O2 may be corre- 

 lated with the increased rate of cation transport involving chemical reactions 

 in the sickled cell (109). 



Dog Red Cells 



Frazier et al. (23) have measured K transport in dog red cells as a function 

 of the K concentration in the medium. They found that K influx into separated 

 dog red cells (white cells discarded) could be described by the relation (fig. 4) 



'Mk = 0.028 [K],„ - .003 



This value for D'k may be compared with the value .016 derived from the 

 flux ratio analysis of their data (tables i, 2). In the calculation of "Ick it was 

 assumed that K outflux was .11 mM/(l. RBC) X (hr.) and [K]c — 8.35 mn/ 



DOG CELLS - 38° C 



Fig. 4. K influx into dog red cells is 

 plotted as a function of K concentration 



in the medium ([K™]). 



kg H2O, their mean values. These values for D'k in dog cells are not too dif- 

 ferent from the values of .011-. 018 obtained for human cells. The apparent 

 activation energy for K influx in dog cells is 12,000 cal/mole. 



Measurements of Na transport in dog cells (95) do not include the eff'ect of 

 variations of [Na],„ in Na influx. However, inspection of the rate constants 

 shown in table i shows that the ratio of the inward to outward rate constant 

 for Na transport closely approximates that predicted for diffusion. The value 

 of D'xa = 'kNa = .093 is considerably higher than the value of .021 obtained 

 for human red cells at 37°C. 



Thus, K and Na transport in dog red cells can, in large part, be accounted 

 for according to diffusion theory. Furthermore, the effective diffusion coef- 

 ficient for K in the dog cell membrane is not appreciably greater than in the 

 human cell membrane. The main difference in the cation transport apparatus 

 of the two cell types appears to be the presence of a system of chemical reac- 



