984 



ADVENTURES IN RADIOISOTOPE RESEARCH 



(a) Life-time of the Avian Red Corpuscles 



In the determination of the life-cycle of avian red corpuscles, erythro- 

 cyte samples are secured daily after injection of labelled sodium phos- 

 phate (about 15 iJLG.) to the hen, and the radioactivity of their deoxyribo- 

 nucleic acid P is determined. The specific activity of the plasma inor- 

 ganic P is determined as weh. In Fig. 5 the broken line indicates the 

 change of the specific activity of plasma inorganic P with time, and the 

 full hne shows the corresponding values of deoxyribonucleic acid P. 



36 



32- 



28- 



o 



o 



O 24 



■^ 20 



\ Plasma inorganic P 



\ Red corpuscle deoxyribonucleic acid P 



\ 

 \ 

 \ 

 \ 



-1 \ \ r 



16 20 24 28 

 Time, days. 



Fig. 5. 



Change of the specific activity of phosphorus fractions of 

 the hen's blood with time (Ottesen). 



The radioactivity of the deoxyribonucleic acid P of the red corpuscles 

 formed during the first day constitutes a very large part of the radio- 

 activity of the deoxyribonucleic acid of the total red corpuscle content 

 of the circulation. Correspondingly, as soon as the life-cycle of the red 

 corpuscles formed during the first day after injection of labelled sodium 

 phosphate is accomplished, the activity of the deoxyribonucleic acid P 

 of the total corpuscles rapidly declines, as seen in Fig. 5. The date of 

 this rapid decline indicates almost precisely the life-cycle of the avian 



red corpuscles. 



To arrive at a correct value of the life-cycle of the deoxyribonucleic 

 acid the contribution of red corpuscles formed in a later part of the 

 experiment to the activity of the total erythrocyte deoxyribonucleic 

 acid must be taken into account as weh. This can be done by making 

 use of the following consideration. The formation of lal)elled deoxyribo- 

 nucleic acid during the first day takes place with participation of 



