KATE OF PENETRATIOX OF IONS INTO ERYTIIKOCYTES 495 



of the plasma constituents get adsorbed on the surface of the corpuscles 

 and a very short time may suffice to replace adsorbed non-lal)elled 

 phosphate ions by labelled ones. 



Furthermore, it is seen in Fig. 1 that the rate of penetration of the 

 pliosphate ions into the corpuscles is a fairly slow process. After the 

 lapse of 1 hour, 1 gm of plasma contains about twice as much ^^p atoms 

 as 1 gm of corpuscle. From 100 ^ap atoms added to the blood, about 

 37 are found in the corpuscles, and 63 in the plasma. 



EXPERIMENTS OF LONG DURATION 



Since the composition of drawn blood changes on standing, it is not 

 advisable to cany out experiments with drawn blood lasting more than 

 a few hours. 



Information about the amount of ^'^P which penetrates into the cor- 

 puscles in the course of several hours or days can be obtained through 

 experiments carried out in vivo (Aten and Hevesy 1939). The results 

 of such experiments are seen in Table 1. The specific activity stated is 

 the ratio of the ^ap and the total P content of the sample. The specific 

 activity of the plasma inorganic P is taken to be 100. 



In the case of a complete interchange between plasma inorganic P 

 and corpuscle acid soluble P these P fractions should have the same 

 specific activity. If the ratio of the specific activity of the inorganic P 

 of the plasma and the P of the corpuscle is, for example, 10, then every, 

 tenth acid soluble corpuscle P atom got replaced by P atoms present in 

 the plasma at the start of the experiment. In all these experiments, the 

 activity level of the plasma was kept approximately constant. This state 

 was obtained by injecting labelled phosphate to the rabbit throughout 

 ihe experiment. 



In the first phase of the experiment, the rate of accumulation of ^~P 

 in the corpuscles is slower than the rate of incorporation of ^^p into the 

 easily hydrolysable organic P compounds which takes place inside the 

 corpuscles. The rate of formation of active, easily hydrolysable P com- 

 pounds is, thus, regulated by the speed of intrusion of ^^p into the cor- 

 puscles. The renewal of some of the "non-hydroly sable" organic P com- 

 pounds takes place at a comparatively slow^ rate, and the rate of for- 

 mation of active molecules of such compounds is not regulated by the 

 influx of 32p into the corpuscles but by the speed of new formation of 

 these "non-hydrolysable" acid soluble P molecules. After the lapse 

 of 9 days, we still find in the corpuscles not renewed acid soluble P 

 molecules, while practically none are present after the lapse of 50 

 days. During this interval, the major part of the corpuscles has also 

 been renewed. 



