Porphyrins fecal porphyrin excretion

Each laboratory should establish its own reference values. Those given here can only be interpreted as a guide. To our knowledge, the age dependence of fecal porphyrin excretion has not been studied. The following values for coproporphyrin I, coproporphyrin III, and protoporphyrin represent the meant two standard deviations ( 2SD) and were assessed in samples from adult volunteers <20, < 12, and < 80 nmol/g dry weight, respectively. 

In adults, measurement of fecal nitrogen and fat in 72-hour specimens is used to assess the severity of malabsorption measurement of fecal porphyrins is occasionaEy required to characterize the type of porphyria (see Chapter 32).UsuaEy, no preservative is added to the feces, but the container should be kept refrigerated throughout the coEection period and care should be taken to prevent contamination from urine. When the collection is complete, the container and feces are weighed, and the mass of excreted feces is calculated. The specimen is homogenized and ahquotted so that the amount of fat or nitrogen excreted per... 

In PCT, excretion and plasma porphyrin concentrations return to normal during remissionj with the proportions of individual porphyrins in urine and feces remaining abnormal for longer than total porphyrin concentrations. Thus in a patient whose skin lesions have healed, and whose total urinary and fecal porphyrin concentrations are normal, determination of individual porphyrins may reveal the diagnosis. The plasma fluorescence scan in VP and fecal coproporphyrin-III excretion in HCP remain abnormal for many years after clinical remission. 

The plasma porphyrin concentration may be increased in conditions in which porphyrin excretion is impaired, such as renal failure and cholestasis. Although plasma porphyrin concentrations are usually higher in chronic renal failure with PCT than in renal failure alone, unequivocal diagnosis of PCT in this situation is best achieved by fecal porphyrin analysis or fractionation of plasma porphyrins by HPLC. ... 

Rose IS, Young GP, St John DJ, Deacon MC, Blake D, Henderson RW. Effect of ingestion of hemoproteins on fecal excretion of hemes and porphyrins. Clin Chem 1989 35 2290-6. 

Uroporphyrinogen decarboxylase (EC 4.1.1.37). The enzyme is unstable. Increased fecal excretion of uroporphyrin, porphyrins possessing 7 carboxylic add groups, copropoiphyrin and isocoproporphyrin. Phot ennatosis. Hepatic siderosis. Risk of primary hepatocellular carcinoma greatly increased. Treatment by phlebotomy. Autosomal dominant. The condition may also be induced by exposure to halogena-ted aromatic hydrocarbons (e.g. polychlorinated biphenyls, hexachlorobenzene). 

In the normal human the excretion of porphyrins in the urine per day (Table X) may amount to 100 /tg of which COPRO-I isomer is the main component lesser amounts of COPRO-III and only traces of URO are excreted (SffO). In the feces about 0.5 mg of a mixture of COPRO, PROTO, and deuteroporphyrin are excreted per day. The traces of deuteroporphyiin (Fig. 1) are assumed to be formed by the action of the intestinal bacteria on the excreted porphyrins and heme fecal porphsrrin is due miunly to syntheffls by intestinal flora as well as to chlorophyll derivatives (e.g. phylloerythrin) from ingested vegetable material (4). 

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