512 ADVENTURES IN RADIOISOTOPE RESEARCH 



between plasma ami corpuscles did, thus, not much differ from the cor- 

 responding distribution ratio of ^sj^a as the sodium content of 1 gm 

 of corpuscle amounts to about I of the sodium content of 1 em of 

 plasma. The specific activity of the sodium of the corpuscle did, thus, 

 not much differ from the specific activity of the sodium of the plasma. 

 Hence, we have to conclude that in the course of the experiment the major 

 part or all of the corpuscle sodium interchanged with plasma sodium. 



Experiments of short duration in which labelled sodium was administer- 

 ed by intravenous injection to the rabbit showed that the rate of inter- 

 action of the plasma sodium with the corpuscle sodium is not slow. 

 After the lapse of 15 minutes, the activity of 1 gm of corpuscles was 

 found to amount to 11 per cent of that of 1 gm of plasma (Table 14). 



In another experiment, after the lapse of 11 minutes, the percentage 

 ratio was found to be 9. 



The comparison of the permeability of the wall of the corpuscles of 

 the rabbit to sodium and to chloride is made difficult by the fact that 

 the sodium content of the rabbit corpuscles is very low and amounts 

 to only about ~ of the sodium content of the plasma. The amount of 

 labelled sodium adsorbed on the corpuscle membrane may, therefore, 

 constitute quite an appreciable part of the labelled sodium found in the 



Table 14. — Distribxttion of 2*Na administered 



BY Intravenous Injection between Corpuscles 



AND Plasma of the Rabbit 



€entrifuged corpuscles. Furthermore, when only a fraction of the sodium 

 ions of the plasma have penetrated into the corpuscles a proportional 

 distribution of 24Na between plasma and corpuscles will be reached, 

 which is not the case for ^^Cl, since the concentration of chloride in the 

 plasma and the corpuscle water differs only to a minor extent. The cor- 

 puscle water of the dog contains, however, nearly as much sodium as 

 the plasma water and, therefore, the corpuscles of the dog and also the 

 corpuscles of the cat are more suitable to be used in experiments in which 

 the permeation of sodium is to be compared with the permation of chlo- 

 ride. W. E. and E.T.Cohn (1939), who where the first to determine 



