"K LABELLED RED COKl'USCLES IX BLOOD VOLUME MEASUREMEXTS 575 



As distribution coefficients of^-K between 1 gm fresh corpuscles and 1 

 gm fresh plasma at 37° C in three experiments, each taking 15 minutes, 

 the values of 0.200, 0.209 and 0.205 were obtained. The mean value is 

 thus 0.205. Levi (1945) found a distribution coefficient of 1 after llie 

 lapse of 1 hr, while Mullins and assoc. (1941) determined the time 

 necessary to reach a 30 per cent exchange between corpuscle potassium 

 and plasma potassium to 8.2 hr. 



Since this paper went into press we became cognizant of a paper by 

 IIakker et al. (1950) and of several papers by Sheppard ct al. (1950,, 



T 1 1 1 1 r 



5 10 20 30 40 50 60 120 



Minutes after injection 



Fig. 2. Change in ■'-K content of red corpuscles after injection of 

 washed labelled corpuscles. Value obtained for the red blood corpu- 

 scle volume 2220 g. 



1951) dealing with the in vitro exchange of potassium between red cor- 

 puscles and plasma. Rakker et al. succeeded in maintaining erythro- 

 cytes in an essentially normal state for over 48 hours and in showing 

 that after the lapse of that time the specific activity of plasma potassium 

 and red corpuscle potassium becomes equal, thus a total interchange 

 between plasma potassium and corpuscle potassium takes place within 

 that interval. They arrive at the result that at 37 °C 1.6 per cent of the 

 potassium of the erythrocytes exchange per hour. Numerous data are 

 stated by Sheppard et al. for the extent of potassium interchange be- 

 tw^een plasma and erythrocytes after different times and under different 

 experimental conditions. Their data contain also figures for an incubation 

 time of 17 — 18 min only. When calculating from their figures the ^-Iv 

 loss by the red corpuscles under that time interval, we arrive to a figure 

 of 1.0 — 1.3 per cent, a result which compares with the loss of 1.0 per 

 cent observed by us in experiments taking 15 minutes. From their results 

 obtained when incubating blood in the presence of ^H\. for 2 min only, 

 one can conclude that during 2 min an ^^K loss as large as 0.4 to 1.1 

 per cent takes place. On the other hand from the experiments of Shep- 



