1016 



ADVENTURES IN RADIOISOTOPE RESEARCH 



measurement of the change of concentration during a definite interval 

 thus permits the output to be expressed as volume of flow per time unit. 

 By a blood volume of 6.11 litres for example, the dilution curve indi- 

 cates an output of 5.48 1/min. 



The most perfect labelling of red corpuscles is achieved by introducing 

 radioactive iron into the haemin, which however in mammalia only takes 

 place in vivo during its formation in the bone marrow. In clinical experi- 

 ments iron labelled red corpuscles cannot be applied as they necessitate 

 a donor to whom a radioiron sample of an unpermissibly high radio- 

 activity must be administered. In clinical studies in the course of the 



100 



(Polycythemia vera 

 I Secondary polycythemia 

 k Relative polycythemia 



50 60 



Hematocrit 



80 



Fi&. 15. — Haematocrit plotted against red corpuscle volume. 



first decade following the introduction of radioactive labelling of red 

 corpuscles mostly '^^p labelled red corpuscleswere applied. Occasionally 

 also such labelled with ^H^ or ThB. 



Recently labelled chromate^"^ is much used in the determination of red 

 corpuscle volume. Chromate is conserved for a long time in the erythro- 

 cytes, half of the radioactive label being lost after the lapse of 26 days 

 only. Furthermore by following the radioactivity of chromium labelled 

 red corpuscles for many days we can get information whether their life- 

 span is normal or shortened as in the latter case the half- value of the 

 loss of radiochromium is shortened as well. Important clinical information 

 can thus be obtained by following the rate of release of ^^Cr by the 

 in vitro labelled red corpuscles reinjected into the circulation. In the 

 labelling with ^^Cr, red corpuscles of all ages are involved, and this is 

 also the case when applying Ashby's differential agglutination tech- 

 nique. It is occasionally of interest to label red corpuscles built up at a 

 certain date, i.e. within an interval of some days only. This can be 

 achieved by administering i*C labelled glycine, 8 out of the 34 carbon 



