Studies of Coproporphyrin. Ii. an Investigation of the Contribution to the Urinary Coproporphyrin of Hemoglobin and of Bacterial Metabolism in the Intestinal Tract.

Stokvis (1) advanced the idea that blood in the intestinal tract was the source of the urinary porphyrin. Schumm (2) also held this belief. Subsequent studies, notably those of Fischer and Hilmer (3), Brugsch (4, 5), and Kaunitz (6) indicated that a variable fraction of the urinary coproporphyrin was thus derived. The presence of a porphyrin in meconium (2, 7, 8), later identified by Waldenstr6m as coproporphyrin I (9), together with a number of other evidences of an endogenous formation, which are discussed in detail in recent reviews(10, 11), have made it reasonably clear that at most not more than a certain fraction of the, urinary coproporphyrin (UCP) could be regarded as originating in the intestinal tract. The purpose of the present investigation was to obtain more definite information as to the size of this fraction, under various experimental and clinical conditions. It was also determined to study the relative percentage of coproporphyrin isomers composing any increases which might be observed, since previous studies bearing on these questions had dealt only with the total coproporphyrin. It was conceivable on a priori reasoning, that any one or a combination of the following might alter the total coproporphyrin concentration or the isomer distribution in the urine: (1) A formation of coproporphyrin III from hemoglobin, by the bacterial flora of the colon, with reabsorption and excretion in the urine. Jakob (12) showed that pure cultures of E. coli produce small amounts of coproporphyrin III in the presence of hemoglobin. Snapper (13-15)