566 XI. HEMOGLOBIN CATABOLISM, I 



cient rats, and concluded that 75% of the liver iron, 40% of the spleen iron, 

 and 15% of the bone marrow iron was mobilizable storage iron, while 15-25% 

 constituted tissue iron, the remainder being due to hemoglobin. 



Radioactive iron, injected intravenously as ferric ammonium citrate, is 

 readily converted into liver ferritin by the dog (Hahn and co-workers, 1089; 

 Granick and Hahn, 1036). Thirteen days after the injection, 80% of the 

 injected Fe^' could be recovered from the ferritin fraction of the dog's liver. 

 About 50% of the iron set free by destruction of hemoglobin by means of 

 phenylhydrazine was stored in the liver {1089,1729). The spleen, which 

 before the injections contained relatively large amounts of ferritin, did not 

 take up much of the injected ferric citrate iron, but took up more of the 

 broken down hemoglobin iron, although less than the liver. 



Greenberg and co-workers (100,480) studied the storage of radioactive 

 iron in the organs of young (normal and anemic) rats, after removal of blood 

 by viviperfusion. The liver is the chief storage organ, the spleen the next in 

 importance. A considerable amount is also stored in the intestinal mucosa. 

 Far more iron is stored in the liver after intravenous administration of the 

 iron than after feeding; the storage of iron by the liver is evidently con- 

 trolled by the plasma iron concentration. Only a small amount (2-6%) is 

 stored in muscles and this is not influenced by the degree of anemia; (in the 

 earlier paper of Austoni and Greenberg a much larger uptake by the muscles 

 had been claimed). After oral application the highest specific activity 

 (Fe^y total Fe) was found in the bone marrow, although the experiments 

 indicated a preliminary passing storage in liver and spleen; after intraperi- 

 toneal application, particularly in anemic rats, the specific activity in the 

 liver was higher than that of the bone marrow.* 



Under pathological conditions, large amounts of iron can })e stored in the 

 liver and spleen; in hemochromatosis the liver can contain up to 30 g. of 

 iron. The life curves of nonhematin iron in the liver and kidney and of hemo- 

 globin in the blood are closely parallel, except that little evidence was found 

 for a sex difference in storage iron {SGI). 



10.3.4. Estimation of Nonhematin and Hematin Iron. A number of 

 methods for the estimation of nonhematin iron have been worked out, some 

 of which have been discussed in the sections on nonhemoglobin iron in the 

 blood in Chapter X, Section 5. For the estimation of nonhematin iron in 

 tissues the best method available is probably the modification of tliat of 

 Tompsett {2817), by Briickmann and Zondek {S(J2). The tissue is boiled for 

 seven minutes with a mixture of trichloroacetic acid and pyrophosphate, 

 which removes the iron from ferritin, and the iron in the extract is determined 

 colorimetrically as the o-phenanthroline complex, after neutralization and 

 reduction. A small part of hemoglobin iron (probably about 2%) may be 

 split off by this procedure, but this is usually of no significance. Hematin 

 iron is found as the difference between total and nonhematin iron. 



A direct estimation of hematin iron has been suggested l)y YabusoeG^^^C*) 

 who extracts the hematin with methyl alcohol containing hydrochloric 

 acid, removes proteins by magnesium sulfate precipitation, and determines 



* Cf. also Dubach, Moore, and Minnieh {G-i5a) and Vannotti {2S0Oa). 



