The conversion of hematin to bile pigment.

The role of hem&in in hemoglobin and bile pigment metabolism is not clearly defined. Opinion has been divided over the questions of whether or not hematin is a normal degradation product of hemoglobin and whether or not it is converted to bile pigment. Bingold observed that the occurrence of hen&in in the plasma is associated with a variety of pathologic conditions (1). The conditions in which hematinemia has been observed by him and others include hemolytic anemias, hemoglobinuria, pernicious anemia, severe liver disease, and large blood extravasations. It has been noted in the fetus during the second half of gestation and in umbilical cord blood (2). Duesberg (3) claiied that under normal conditions hemoglobin is quantitatively converted to bile pigment and that hematin appears only in pathologic conditions. The studies of Fairley (4) indicate that hematin in the plasma unites immediately with albumin to form methemalbumin. This substance is not found normally; it occurs, according to Fairley, as a result of intravascular hemolysis, whereas normally hemoglobin degradation occurs in the reticula-endothelial system and is converted to bile pigment without an intermediate stage of methemalbumin. Attempts to determine whether hematin is converted to bile pigment have consisted for the most part in injections of hematin and measurements of bile pigment excretion. Brugsch and Kawashima (5) and B&rard et al. (6) found increased excretion of biirubm in dogs, and Pass, Schwartz, and Watson (7) found increased excretion of urobilmogen in man following intravenous injection of hematin. On the other hand, no increase in bilirubin excretion in man was found by Duesberg (3), and Gitter and Heilmeyer (8) observed an increase in urobilinogen excretion in but one of two men following injection of hematin intravenously. The conclusion, on the basis of this type of experiment, that bile pigment has been derived from hematin is subject to the criticism that the increased bile pigment excretion may not represent actual conversion of hematin to bile pigment but may be an indirect effect of the injection of hematin. Studies of