564 



ADVEXTURES IN KADIOISOTOPE RESEARCH 



activity which penetrates into the corpuscles in the course of 25 minutes. 

 The penetration of radio-phosphorus in the corpuscles during the experi- 

 ment increases the activity of the corpuscles and, thus, makes the total 

 corpuscle content of the circulation appear too low. The error in an 

 experiment lasting 10 minutes amounts to 5 per cent. 



(C) 1.5 per cent of the radio-phosphorus content of the corpuscles 

 was found to be replaced by inactive phosphorus from the plasma in 

 the course of 10 minutes. This loss ascertained in experiments in vitro 

 makes the dilution figure and, thus, the corpuscle content of the body 

 appear too high. That the loss of radio-phosphorus by corpuscles in the 

 course of 10 minutes is markedly restricted, is not due exclusively to the 

 fact that the phosphate ions penetrate only at a moderate rate through 

 the corpuscle membrane, but also to the following. 1 gm corpuscles 

 contains about -/g as much inorganic P as 1 gm plasma and, moreover, 

 comparatively large amounts of readily exchangeable organic P present 

 in adenosintriphosphate and also in hexosemonophosphate, and some 

 other acid solul)le organic P compounds. The concentration of such 

 readily exchangeable P atoms in the corpuscles is with an order of 

 magnitude larger than the concentration of inorganic phosphorus. 

 As soon as the active P atoms enter the corpuscles, they interchange 

 with phosphorus atoms present in the organic compounds. After 2 hours 

 shaking of the blood in the presence of labelled phosphate, a large part 

 of radioactive P atoms present in the corpuscles will, thus, be found in 

 the organic fraction and, consequently, the activity of the inorganic P 

 of the corpuscles will be kept at an appreciably lower level than the 

 activity of the inorganic P of the plasma. 



An estimate of the different experimental errors in the determination 

 of the red corpuscle content is seen in Table 3. The data of this table 

 reveal that the value of the red corpuscle content obtained in experiments 

 lasting 10 minutes is 0.5 per cent too low, the error being smaller in 

 •experiments of shorter duration. 



Plasma volume determination by the means of the dye method 



In a number of cases, the plasma volume was determined by means 

 of the dye method described by Gibson and Evelyn (1938). In this 



Table 3. — Estimate of Diffeeent Errors of Experiment in the 

 Determination of the Erythron 



