518 BLOOD VOLUME DETERMINATION 



DETERMINATION OF BLOOD VOLUME BASED ON THE DILUTION 



OF LABELLED CORPUSCLES 



In this note, we wish to describe a method of blood volume deter- 

 mination based on an entirely different principle from that described 

 above. We inject into the vein of a rabbit A a known volume of labelled 

 corpuscles taken from another rabbit B and determine the extent to 

 which these labelled corpuscles are diluted in the circulation of rabbit A. 

 Labelled corpuscles of rabbit B are obtained in the following way. We 

 administer by subcutaneous injection some labelled (radioactive) sodium 

 phosphate to rabbit B. In the course of about a week, a substantial 

 fraction of the phosphatide molecules of the bone marrow and other 

 organs are renewed. As this renewal takes place in the presence of labelled 

 phosphate, the newly formed phosphatide molecules will contain labelled 

 P atoms. Corpuscles formed in a medium containing labelled phosphatide 

 molecules will necessarily incorporate some of them. Labelled phosphatide 

 molecules can also enter to some extent into the corpuscles by exchange 

 of non-active phosphatide molecules with active phosphatide molecules 

 present in the plasma. The various ways of incorporating labelledphospha- 

 tide into corpuscles are described in detail in a paper which is in 

 print (Hahn and Hevesy, 1940). 



Besides labelled phosphatides, labelled varieties of several acid-soluble 

 organic phosphorus compounds as, for example, those of glycerophos- 

 phate and adenosintriphosphate, are found in the corpuscles. Each of 

 these compounds can be used as an indicator when determining the 

 dilution of the corpuscles of rabbit B in the circulation of rabbit A. 

 It is, however, more convenient to extract the total acid-soluble P and 

 to use the mixture obtained as an indicator. 



DETERMINATION OF THE BLOOD VOLUME OF A RABBIT 



WEIGHING 2 kgm 



a) Making use of the labelled phosphatides of the corpuscles 



We administered radioactive sodium phosphate of negligible weight 

 leaving the activity of about 0.001 milliCurie to rabbit B. After the 

 lapse of a week, 1 cc. of blood of rabbit B containing 0.32 cc. cor- 

 puscles was injected into the jugularis of rabbit A. After the lapse of 

 5 min, 50 cc. blood were collected and, after the addition of heparin, 

 centrifuged. The haematocrit value of this sample was found to be 0.33. 

 The phosphatides of the corpuscles were thoroughly extracted by Bloor's 

 method. Their P was converted by wet ashing into phosphate. The 

 phosphate was precipitated as ammonium magnesium salt. Before 

 precipitation, sodium phosphate was added to the solution to obtain 

 a precipitate of about 80 mgm. The activity of the precipitate was then 

 determined by means of a Geiger counter. The comparison of the acti- 



