132 



ELECTROLYTES IN BIOLOGICAL SYSTEMS 



1.9 mM/(l. RBC) X (hr.). The corresponding value for c^lNa is 2.8 mM/ 

 (1. RBC) X (hr.). These values can now be compared with the values for D' 

 obtained from the variation of K and Na influx with the concentration of the 

 ions in the medium (table 2). 



Variation of fluxes with concentration. Figure i is a plot of the available 

 data on the relation of K influx to the K concentration in the medium. K influx 

 into human red cells becomes relatively independent of the K concentration 

 in the medium when the latter is above 4 mM/1. This behavior would be ex- 

 pected if most of inward transport of K in human red cells involved a chemical 

 reaction. We will assume that this non-diffusion influx is independent of 

 [K]m when the latter is greater than 5 mM/l. In this region, equation 8 will 

 describe the curve. Then the slope of the line relating ']\Ik to [K],n in the 

 region of the curve above [K]ni = 5 mM^l. represents Dk' , and the intercept 

 on the ordinate represents c^Ik • In figure i are plotted all of the presently 



Fig. I. K influx into normal 

 human red cells is plotted as func- 

 tion of K concentration in the 

 medium ([K]m). Symbols refer to 

 measurements made by different 

 authors. The symbol followed \>y 

 the reference to the work are as 

 follows: • (100), A (95), O (87), 

 A D. C. Tosteson, published here 

 for first time. 



available data relating K influx to K concentration in the medium. Included 

 are all of the previously published data (87, 95, 100) and hitherto unpublished 

 experiments made in our laboratory. All of the experiments were done at 

 37°C. The straight line portion of the curve was obtained by the least square 

 analysis of all experiments in which [K],„ > 5 mM/1. The value of D'k obtained 

 from the slope of this part of the curv^e is .011 db .29, while the value of cMr 

 is 2.14. This value of D'k is not significantly different from the value of .017 

 obtained by the flux ratio method. However, it also does not differ significantly 

 from zero. Therefore, the available data neither prove nor disprove the idea 

 that all of K outflux and a portion of K influx is by diffusion. 



All of the hitherto published measurements of K influx as a function of 

 external concentration save those of Raker el al. (87) were made at [K],„ values 

 of less than 20 mM/1. Raker et al. report single experiments at K concentrations 

 of 38 and 74 mM/1. in the medium. Their flux values were derived from meas- 

 urements of the radioactivity in the medium and whole blood as a function of 



