484 ADVENTURES IN RADIOISOTOPE RESEARCH 



the corpuscles acid-soluble P are thus in good agreement. We arrived 

 at the calculated figure by making use of the a value obtained 

 with rabbits' blood in experiments in vitro (taking a = 0.0013 for 

 rabbit I) .<i) 



ADMINISTRATION OF LABELLED HEXOSEMONOPHOSPHATE 



Labelled hexosemonophosphate containing 6 mgm. P was administered 

 to a rabbit weighing 2.7 kgm. by intravanous injection. After the lapse 

 of 1^ hours the animal was killed and the specific activity of the fractions 

 recorded in Table 5 determined. 



When interpreting the above figures we must bear in mind that the 

 greatest part of labelled inorganic P formed through the decomposition 

 of active hexosemonophosphate enters the tissues. That the specific 

 activity of the plasma inorganic P is, in spite of this fact, higher than 

 that of the plasma ester P clearly indicates that a very large part of the 

 active hexosemonophosphate injected into the blood must have been 

 decomposed in the course of the experiment. We must also take in 

 consideration that besides the 4 mgm.% hexosemonophosphate P added 

 the plasma contained also its normal ester P content of about 0.5 mgm.% 

 which became partly labelled, this being made possibly through the 

 presence of labelled inorganic P formed through the decomposition of 

 active hexosemonophosphate. But even disregarding the presence of 

 esters other than hexosemonophosphate, by comparing the activity of 

 the hexosemonophosphate introduced with that of the total plasma 

 ester present, after the lapse of l| hours, we arrived at the result 

 that more than 99.9% of the labelled hexosemonophosphate adminis- 

 tered left the circulation within 1 1 hours. In making the above cal- 

 culation we assumed the blood content of the rabbit to amount to 

 160 cc. 



In our in vitro experiments ^/^j mgm. of hexosemonophosphate was 

 added to 10 cc. blood, thus the concentration of the latter was about 

 ~ of that in the experiment in vivoS^ While in the in vitro experiment 

 in the course of 2^ hours | of the labelled hexosemonophosphate was 

 decomposed, in the in vivo experiment in the course of 1 ^ hours more 



(^) When isolating the inorganic P and the different fractions of the ester P present 

 in the corpuscles and comparing their specific activity in experiments in vitro 

 and in vivo some differences were found. The results of these experiments will 

 bo shortly published. 



