NONHEMATIN IRON IN TISSUES 565 



of the plasma iron by blockage of the reticuloendothelial system with thorium 

 dioxide (156,2705) may be due to the decrease of hemoglobin breakdown. 



Vahlquist (^<S'44) found the plasma iron in the fetus to increase gradually 

 to about loO ng. per 100 m., followed by a sharp drop after birth and a slow 

 gradual rise later. The plasma iron life curve thus follows closely that of the 

 hemoglobin content of blood. 



In infections, a drop of plasma iron is often accompanied by an increase 

 of copper (1222). This countermovement of iron and copper has also been 

 found by several observers, but does not occur invariably (cf. Chapter XIII, 

 Section 3.3.4.). Houghton and Doan (1350) suggest that the rapid fall of 

 plasma iron in remission from pernicious anemia may be used for measuring 

 the activity of the antipernicious anemia principle in liver extracts. 



The plasma iron is nonhematin iron, ferric (2(ilS), and is set free by tri- 

 chloroacetic acid (.9^-'<s')- Tompsett (2810) assumed that it may be iron pyro- 

 phosphate, but it is nondialyzable and bound to protein (2400. 284-^,3 152). 

 Vahlquist (284-4) found some bound to serum albumin, some to globulins; 

 even at a low pK some remained undialyzable. By using the precipitin 

 reaction for the detection of apoferritin, Granick (1032) has shown the 

 absence of this protein from plasma. Ferritin is thus of no importance in 

 iron transport. 



10.3.3. Storage Iron. The iron found in tissues is either a continu- 

 ous and essential part of the tissue, or is storage iron, which can be 

 mobilized if required for the synthesis of hemoglobin. Most of the 

 latter iron is stored in the liver, the kidney (361), and the spleen. 

 Tissue iron consists mostly of hematin iron (respiratory ferments, 

 myohemoglobin), but also apparently of some nonhematin iron, 

 while storage iron is entirely nonhematin iron, probably largely 

 ferritin (cf. below). 



Of the large number of studies on the iron content of organs we can men- 

 tion only a few. Different methods and different animals have been u.sed by 

 the investigators, which makes a short summary difficult. 



The liver is the organ in which most of the iron is stored. According to 

 Brlickmann and Zondek (3<)1) the human liver contains on the average 

 1080 mg. iron (800 mg. per kg.) of which 15% is nonhematin iron: tlie kidney 

 contains 410 mg. (1(50 mg. per kg.. 40% nonhematin iron). While the amount 

 of hematin iron in both organs is about the same, the liver contains five 

 times as much nonhematin iron, most of which is storage iron. The spleen 

 contains less iron than either of these organs (2613), but the concentration of 

 nonhematin iron in this organ equals that in the liver (2817). In rats' liver 

 Tompsett (2817) found about .50% of the iron as nonhematin iron, which 

 does not agree well with the observations of Scott and McCoy (2520), who 

 found that the storage iron of the liver contributed 75% of its total iron. 

 These workers found 80(> /ig- ''""'i i" '"at liver, 13.5 jUg. in the spleen, and about 

 20 jug. in the bone marrow. They tried to estimate the amount of storage 

 iron by studying the iron contents of these organs in normal and iron-defi- 



