EFFECT OF IRRADIATION OX HEMIX FOKMATIOX 629 



Delay of the effect of irradiation on the incorporation of labelled iron 

 into hemoglobin 



Red corpuscles are very radioresistant. We need very massive doses 

 to achieve hemolysis and a dose of 4000 r for example as shown by 

 Sheppard^^*^ does not influence the rate of intrusion of ''^K in the red 

 corpuscle though it does to some extent weaken the mechanism respons- 

 ible for the concentration of potassium in the red corpuscles. Dog blood 

 exposed to a dose of 200,000 r doesnot hemolyse as observed by Nizet 



et alP^^ 



The radioresistance of circulating red corpuscles suggests that the not 

 fully completed red corpuscles in the bone marrow are radiation resistant 

 as well and continue even in the exposed animal to complete their hemo- 

 globin content. In the bone marrow of swine exposed to radiation of the 

 Bikini explosion often only fat cells and a few clumps of erythrocytes 

 were found^^^\ 



The above conclusion is supported by the observation that the uptake 

 of ^^Fe or ^^C by the hemoglobin of red corpuscles in vitro is not reduced 

 by irradiating the animal before securing the blood sample. Reticulocytes 

 and other types of incomplete red corpuscles can complete their hemo- 

 globin content in vitro. Not only is the ^^C incorporation in vitro into 

 the blood corpuscles of animals not smaller than into those of 

 controls, it is even markedly enhanced as shown by Nizet et alS^^^ 

 who investigated the uptake of "C by the dog. Rauntanan and one 

 of us made similar observations when studying incorporation of ^^Fe 

 in vitro into the red corpuscles of the hen which was found to be increased 

 in extreme cases up to 300% if the hen was 18 hours previously exposed 

 to a dose of 1000 r. Irradiation induces presumably the bone marrow 

 to release some of the red corpuscles in an earlier stage of their matura- 

 tion. Nizet et al. have furthermore shown that irradiation in vitro 

 produces changes in the plasma which are favourable to ^^Fe incorpora- 

 tion into the red corpuscles. 



These considerations support the conclusion that as far as red corpu- 

 scles in the advanced stage of their maturation are present in the bone 

 marrowy a completion of their hemoglobin content takes place even in 

 the exposed organism and that some of the ^^Fe administered shortly 

 after irradiation will be utilized by the bone marrow. With increasing 

 lime the completed red corpuscles being discharged into the circulation 

 or wiped out in the exposed organism, the utilization of ^^Fe by the bone 

 marrow will diminish and after the lapse of about 1 day may almost 

 cease. As the non-utilization of labelled plasma iron by the bone-marrow 

 leads to a depressed turnover rate of the plasma iron, this depression is 

 to be expected not to be shown to its full extent already shortly after 

 irradiation but only at a later date. That this is the case is demonstrated 

 by Fig. 1 and the data of Table 2. 



