Occurrence of the Three Bile Pigments in Biological Material

Occurrence of the Three Bile Pigments in Biological Material 

Pigment II is the main pigment found in bile. In gall bladder bile, up to 30 % of the pigments may occur as pigment I, but in fistula bile not more than 10 % is found in this form. Unconjugated bilirubin appears to be an artifact and can only be detected in grossly infected specimens of bile or in specimens that have been left at room temperature for several hours. 

Verschure et al. (VI) have demonstrated by paper electrophoresis that in gall bladder bile the pigments form part of a lipoprotein complex to which cholesterol and bile acids are also bound. In hepatic bile this complex is not found in appreciable amounts, and the bile pigments are bound to two separate proteins. 

It is generally accepted that in normal subjects, most, but not necessarily all, of the bilirubin formed results from the breakdown of hemoglobin in the reticuloendothelial system. The bilirubin is then conjugated in the liver and excreted into the bile as a water-soluble pigment. The capacity of the liver to conjugate bilirubin is limited (W6), so that in cases of overproduction (e.g., hemolytic jaundice) free bilirubin will appear in the plasma. A similar result will be obtained if the ability of the liver to conjugate bilirubin is diminished (e.g., in the newborn infant). On the other hand, if the excretion of the bile is for some reason 

Electrophoretic studies (G2, M2) have shown that both types of bilirubin are bound to albumin and sometimes a-globulin. Klatskin and Bungards (K6) found that this binding occurs between pH 6 and pH 9 and that below pH 5 separation occurs almost completely with respect to bilirubin but only partially with the conjugated pigment. This suggests that bilirubin and conjugated bilirubin are attached in different ways to plasma proteins. 

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