Originally published in Acta Physiol. Scand. 24, 285. (1951). 



58. APPLICATION OF ^ K LABELLED RED CORPUSCLES 

 IN BLOOD VOLUME MEASUREMENTS 



G. Hevesy and G. Nylin 



From the Cardiovascular Clinic, Soderjukhuset, Slockhohn 



Labelling of red corpuscles by making use of ^^p as an indicator is 

 made possible by the following facts. 



(a) A constant fairly slow interchange of phosphate between plasma 

 and erythrocytes takes place at body temperature. 



(b) The organic labile P content of the red corpuscles is much higher 

 than that of the plasma. 



(c) The individual P atoms, and thus also the ^^P atoms intruded into 

 the erythrocytes, participate in phosphorylation processes and reach 

 rapidly an exchange equilibrium with a part of the labile P present in 

 the red corpuscles. 



Due to these facts, some of the ^^P atoms M'hich when blood is shaken 

 with labelled phosphate penetrate into the erythrocytes in the course 

 of 1 hr, during the same time 1/10 — 1/20 only find their way into the 

 plasma, after injection of the active red corpuscles into the inactive 

 circulation. 



The potassium content of the red corpuscles is also much — about 

 20 times — higher than that of plasma of the same weight and, corre- 

 spondingly, the lifetime of an individual potassium atom in the red 

 corpuscles is about 20 times longer than in the plasma. When introducing 

 *-K atoms into the erythrocytes, we can expect them to leave the red 

 corpuscles at a slow rate only. The loss within 20 minutes, which amply 

 suffice to obtain mixing between the injected and circulating blood, can 

 be expected to be less than one per cent. This induced us to carry out 

 determinations of the circulating blood corpuscle volume by using ^-K 

 labelled red corpuscles. 



EXPERIMENTAL 



To 10 ml of freshly drawn heparinized blood 11— 15 mgm of KCl, previously 

 bombarded in the cyclotron and having an activity of 10—60 juC, were added 

 and the blood was shaken for 2 hrs at 37 °C. In some cases, a known aliquot of the 

 active blood, in others red corpuscles once washed with inactive plasma were 



