EMBRYONAL IRON TURNOVER 66 1 



in the embryo of the exposed rabbit is seen in Fig. 8. The specific acti- 

 vity of the iron of this fraction is much smaller than that of the iron 

 of circulationg hemoglobin in the maternal organism, but appreciably 

 larger in the embryo (cf. Fig. 9). 



Presumably hemoglobin synthesis lakes place l)esides in the cyto- 

 plasm of the hemopoietic liver cells in their nuclei as well. It is of interest 

 in this connection to recall the finding of Stern, Allfrey, Mirsky 

 and Saetren (1952), according to which almost ^g of the hemoglobin 

 of the avian nucleated red corpuscles is present in the nuclei. 



In our experiments during the purification process of the nuclei, the 

 water soluble hemoglobin, present possibly in appreciable amounts, 

 may have been removed, in contrast to the small amounts of water 

 insoluble hemoglobin which amounted to not more than 4.1 mgm in our 

 maternal and 17.5 mgm in our foetal samples. It was found in a previous 

 investigation [BoNNiCHSEN, (1956)] that the radiation sensitivity of the 

 nuclear hemoglobin becomes very marked after the lapse of about 1 

 day, as does that of the circulating hemoglobin. 



Summary 



Seventeen hours after labelling the circulating iron-/Sjglobuhn with ^'Fe, 

 14_ 34 per cent of the labelled iron is found in the 21 days old foetus of the rabbit. 



Exposure of the rabbit to 500 r of X-rays increases the amount of ^*Fe passing 

 the placenta to almost twice the value in non-exposed animals. 



Seventy-three— eighty-three per cent of the ^*Fe content of the embryo is 

 found in the Uver. 



The specific activity of the hemoglobin iron present in the nuclear fraction 

 of the hver amounts to one fourth of that of the circulating hemoglobin in the 

 maternal and to about twice in the embryonal organism. 



Exposure to radiation one day prior to labelling the plasma depresses the frac- 

 tion of embryonal ^^Fe incorporated into the hemoglobin of the nuclear liver 

 fraction to about half of the value observed in non-irradiated rabbits. 



References 



K. Agner, R. Bonnichsen and G. Hevesy (1954) Scand. J. din. Lab. Inv. 6, 



261. 

 E. H. Belcher, J. G. Gilbert and Ll F. Lamerton (1954). Brit. J. Radiol. 27, 



387. 

 R. Bonnichsen and G. Hevesy (1955 a) Acta Chem. Scand. 9, 509. 

 R. Bonnichsen (1956) Acta Chem. Scand. 9, 1045. 



R. Bonnichsen, G. Ehrenstein and G. Hevesy (1956) To be published. 

 L. Heilmeyer (1956) Vortrdge aus dem Gebiet der klinischen Chemie und Cardiologie. 



Thieme Verlag, Stuttgart. 

 T. G. Hennessy and R. L. Huff (1950) Proc. Soc. exp. Biol. 73, 436. 

 R. L. Huff, W. P. Bethard, J. F. Garcia, B. M. Roberts, L. O. Jacobson 



and J. H. Lawrence (1950) /. Lab. din. Med. 36, 40. 



