The Biochemistry of Ferritin 



211 



makes it likely that some of the iron is in the ferrous state and that 

 the complex is dissociable in vivo. The iron could thus be made avail- 

 able for transport to the bone marrow for storage as ferritin. 



4. In response to lowered oxygen tensions, such as occur during 

 anoxia or at high altitudes, some ferritin iron is reduced in the marrow 

 to the ferrous state so that it can combine with protoporphyrin for 



Intestine 

 (absorption) 



X 



Placenta 



(fetal 



absorption) 



H 



''.. 7W<+r\ Aerobic 



Fet^lFe*— f Fe °) " ^ 



H 



Anaerobic 



|[- 



(reduced ferritin) 



(oxidized ferritin) 



-H- 



Fe™^ + Iron-binding protein -«- 



(GSH?) „* 



IBP 



II- 



-44— ^^^ 7FJ*6\ AerotilC - 



Fe% Fe*- L 



Anaerobic 



// H 



Fe~"~ + Protoporphyrin » Heme 



Liver 

 > (storage 

 and release) 



Plasma 

 (transport) 



Bone marrow 

 )> (storage and 

 heme synthesis) 



Fig. 1. Scheme illustrating the participation of ferritin in iron transport. 



heme synthesis. The latter reaction has been reported by Granick in 

 hemolyzates of chick red cells under anaerobic conditions, after addi- 

 tion of inorganic ferrous iron and protoporphyrin. 14 



5. The presence of ferritin in the placenta and the presence there as 

 well of lowered oxygen tensions 15 makes this tissue an ideal one for 

 storage of iron for purposes of transfer from maternal to fetal plasma. 

 Ferritin in the placenta would exist in the ferrous state, and the transfer 

 of iron would take place regularly across the placental barrier to the 

 fetal plasma iron-binding protein. This hypothesis is supported by 

 the observation 13 that in the fetus serum iron is normal or slightly 

 increased and iron-binding capacity is low, whereas in the pregnant 

 woman serum iron is somewhat low or normal and iron-binding capac- 

 ity greatly increased. 



