588 XII. HEMOGLOBIN CATABOLISM, II 



whicli in other instances of acuie porphyria is certainly present as such in 

 the body and in the urine (cf., e.g., Rau, 2213). 



It sliouid also be mentioned that the study of the isomerides has given 

 some contradictory results and others which are hard to explain. We have 

 mentioned in Chapter III that Fischer obtained coproporphyrin I on decar- 

 boxylation of the uroporphyrin of turacin, while Rimington obtained copro- 

 porphyrin III. Coproporphyrin I. not III, was found by Watson and co- 

 workers {2997) after perfusion of protoporphyrin through the liver {cf. 

 Section 3.^2.4.). 



3.3.3. Porphyrins in Normal Excreta. Urine. According to the 

 most reliable modern estimations, between and 120 jig. porphyrins 

 per day are normally excreted in the urine {600,603,2039). 



At first only coproporphyrin I was isolated from normal human 

 urine (771,1298); later Watson (2985) and Fink {766) suspected an 

 admixture of coproporphyrin III, and the latter was finally isolated 

 in almost equal amounts by Grotepass {1062) from 10,000 liters of 

 mixed urine. Dobriner and Rhoads (603) suspected that the mixed 

 urines may have contained some pathologic urines, but, in view of 

 the rarity of pathologic urines in which coproporphyrin III pre- 

 dominates, this can hardly explain the results of Grotepass.* 



Feces. Between 150 and 400 ixg. porphyrins per day are normally 

 excreted in human feces (367,600,603,2039,2850). The meconium 

 contains 2 fig. per 100 g. (980,2098,2099). The amount varies with 

 the diet and part of it is not derived from endogenous metabolism, 

 but is formed in the intestine from hematin compounds of the food 

 or by microbial synthesis (cf. Section 4.5.). Hence, the study of 

 fecal porphyrin excretion does not supply reliable evidence with 

 regard to endogenous porphyrin formation in health, and gives also 

 no clear indications of slightly increased porphyrin formation in 

 disease unless the diet is carefully controlled. This has so far not 

 been done, and the value of these studies on fecal porphyrin excre- 

 tion is therefore limited. Coproporphyrin and traces of protopor- 

 phyrin are excreted in the feces even on a vegetari9^n diet (Fischer 

 and Hilmer, 83^), but their excretion is increased by ingestion of 

 meat and blood (200,2506). Deuteroporphyrin occurs only after 

 ingestion of blood or after hemorrhages into the gastrointestinal tract 

 (297,298,1367). In the human feces coproporphyrin predominates, 

 but protoporphyrin (2098,2099,2986), deuteroporphyrin (2970), and 

 mesoporphyrin (1063,8170) have also been found. In normal human 



* According to Watson and co-workers {-JOOi-aa), coproporijliyriii III forms 8-35% 

 of the total coproporphyriiis. 



