PORPHYRIN METABOLISM 577 



amount of prosthetic group destroyed even in normal hemoglobin 

 catabolism. It may be of importance with regard to porphyrin 

 metaboHsm {cf. Section 3.), which is also small, but can play no sig- 

 nificant role in the balance of hemoglobin catabolism. 



If given per os hematin undergoes a partial decomposition. Of 

 100 mg. hematin given per os 10% was recovered unaltered, while 

 the rest was broken down, a small part by the stomach acid, the 

 remainder by intestinal bacteria (Bing and co-workers, 262). A 

 part of its iron became free and was absorbed, since a negative iron 

 balance was converted to a positive one; other workers, however, 

 found hematin a very inferior source of nutritional iron (cf. Chapter 

 XIII). 



2.4. Toxicity of Hematin 



In 1912 Brown and co-workers (353-356) found that intravenous 

 injections of alkaline hematin solutions into rabbits caused a paroxysm 

 similar to that observed in malaria, and concluded that hematin 

 was the cause of the malarial paroxysms. They found also similar 

 changes in the blood picture and effects on the vascular system, i.e., 

 vasoconstriction followed by vasodilation. These results have 

 I'ecently been confirmed by Anderson and co-workers (55), who found 

 the pathologic changes in the blood vessels and the kidney caused 

 by hematin injection to resemble those in malaria. The renal lesions 

 associated with hemoglobinemia are also ascribed to the toxic effects 

 of hematin on the kidney (5^).* 



Lemberg and Golds worthy {1700) confirmed the observations of 

 Kammerer (1453) that mesohematin has a powerful bactericidal 

 action in concentrations as low as 1/100,000 to 1/1,000,000. The 

 substance turned out, however, to be toxic, 80 mg. in 5 ml. 1% 

 sodium carbonate solution injected intravenously causing the death 

 of a rabbit. 



The toxicity of hematin is one more argument against assuming it 

 to be a normal breakdown product of hemoglobin. 



3. PORPHYRIN METABOLISM 



3.1. Introduction 



In this section we shall discuss porphyrin metabolism excluding the 

 synthesis of porphyrin in the animal body, which is inseparable from 



* In this connection it may he of interest that KeiUn and Hartree {1.501b) found 

 that hematin inhibits the oxidation of succinate f)y heart muscle preparations. 



