Pro-mesobilifuscin (Meso-bilileukan), ein neues physiologisches Abbauprodukt des Blutfarbstoffes

Catabolism of heme in vivo: comparison of the simultaneous production of bilirubin and carbon monoxide

“…A more likely explanation is that part of the hematin was converted in the liver to labeled metabolites that differed from bilirubin and CO which subsequently were excreted in the bile. The nature of these alternate metabolites is unknown; deductive reasoning suggests that they may be di-or monopyrroles (14,17).…”

“…The existence of pathways of heme catabolism that lead to metabolites other than bilirubin is not a novel concept (14). It repeatedly has been postulated that heme compounds may be degraded to pyrrolic derivatives that are smaller and more water soluble than bilirubin (12,33), but the exact mechanisms, the chemical structure of the end products, and the functional significance of these alternate degradative routes have not been established with certainty.…”

“…It is pertinent, however, that in a number of recent experimental studies using isotopic techniques, the yield of bilirubin and of CO appears to fall short of the amount expected on the basis of stoichiometric calculations (11)(12)(13). These and other findings (14,15) suggested the possibility that part of the heme degraded in vivo may be converted to metabolites other than bilirubin and CO. The most direct experimental approach to this problem would be a search for these suspected alternate metabolites of heme.…”

Studies of the Dipyrrylmethene (“Fuscin”) Pigments. I. The Anabolic Significance of the Fecal Mesobilifuscin*

“…Nevertheless the isolation and identification of these oxidation products from the crude pigments, considered in relation to their N percentage and other characteristics, provides strong evidence that their nitrogen was mainly present in a dipyrrylmethene compound. The (3) believed that quantitative measurement of fecal mesobilifuscin might reconcile known discrepancies between the rate of hemoglobin breakdown and fecal urobilinogen excretion. A considerable amount of data collected in various types of anemia reveals that discrepancies of this type are not accounted for by proportionate increases of fecal mesobilifuscin or dipyrrylmethene.…”

Studies of the Dipyrrylmethene (“Fuscin”) Pigments. Iii. The Variable Fate of Bilirubin Depending Upon Conjugation and Other Factors*

“…It has been suggested that the failure to recover urobilinogen after tube-feeding of crystalline bilirubin might be due to conversion of the bilirubin to dipyrrylmethenes such as mesobilifuscin and, similarly, that discrepancies between urobilinogen excretion and hemoglobin destruction might be reconciled by measurement of mesobilifuscin excretion (11)(12)(13). These concepts, however, were not supported by recent studies (14, 15) which indicated that at least the majority of the naturally occurring fecal dipyrrylmethene or mesobilifuscin is anabolic in origin and reflects pyrrol synthesis on the pathway toward heme, rather than hemoglobin destruction.…”