J.Jpn. Surg. Soc.. 57(10): 1643-1662, 1957

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STUDIES ON BILE PROTEINS

Concentrated human bile was studied by means of filter paper electrophoresis with the author's apparatus. Protein detectable in human bile by filter paper electrophoresis may divided into two fractions, namely Fraction-I. and Fraction-II. Normal human bile as well as that of pathological consisted of these components. The component with highest mobility in Fraction-I. was identified as serum albumin, from the fact that it migrated with birilubin, conjugated with brom phenol blue at pH 8.6, and also that it was identical with serum albumin in its position by filter paper electrophoresis of serum albumin- and serum-bile mixture. The remaining constituents of Fraction-I. were confirmed to be composed of α-, β- and γ-globulin.
Fraction-II. of human bile contained mucoprotein, migrating with bilirubin, much higher in its mobility than serum albumin, not conjugating with brom phenol blue at pH 8.6, having amino acids and carbohydrates in its constituents, and coagulating with acetic acid but was not heat coagulable. By ultracentrifuge, it was estimated that mucoprotein was slightly smaller in molecular weight than serum albumin. It was demonstrated on ultracentrifugal patterns that Fraction-II. of pathological bile contained a faster component than mucoprotein. Fraction-II. of pathological bile easily became turbid or was precipitated while kept in the refrigerator. These information might contribute to the further understanding of colloid-chemical explanation of galistone formation.
Lipids stainable with sudan black were detected in Fraction-II. These lipids were easily extracted with anhydrous ethanol, however extraction was difficult with ethyl ether alone, indicating presumably that lipids were combined with proteins in the form of lipoproteins.
Ultracentrifuge have demonstrated that bilirubin migrated with mucoprotein. The absorption maxima of bilirubin in native bile and Fraction-II. indicated 405mμ, however that of dialyzed bilirubin indicated 390mμ. These metachromasy pointed out that bilirubin in bile conjugated reversibly with some high molecular substances such as albumin, mucoprotein and lipoprotein.
Approximately 70% in quantity of bile salts in bile was found to be contained in Fraction-II. Crystal bile salts migrated with the mobility like that of Fraction-II, but they were distributed widely by diffusions during the electrophoresis on filter paper. Accordingly, the fact that bile salts existed in such a high concentration in Fraction-II. might be explained by assuming that the bile salts in Fraction-II. appear there chiefly due to the presumable interaction of bile salts with some high molecular substances such as mucoprotein or lipoprotein, and only in a small proportions, if any, by their own mobility.
Usually, bile salts injure tissues severely, but these bile salts did not injure mucosa of the bile bladder in spite of its high concentration, indicating presumably that the activities of bile salts were decreased due to the conjugation with Fraction-II, and these conjugation might have prevented the absorption through the bile bladder wall of bile salts, too.
Bilirubin and cholesterol are not soluble in water but the main constituent of bile is water , therefore bilirubin and cholesterol in bile were presumably dispersed with certain dispersive substances in a colloidal state. Bile salts, fatty acids and lecithins have usually been regarded as the components in bile with the power to dissolve cholesterol, and recently it was also shown that the lecithin formed a water soluble system with part of the bile salts and that this system could dissolve cholesterol. The β-lipoprotein contained lecithin and cholesterol in its constituents and it was found that the bile includes lecithin and cholesterol, therefore it is presumed that lipoproteins in bile also contain these substances in its constituents. If the lipoprotein in bile is hypothecally similar to β-lipoprotein surface formation, the lipoprotein would absorb and/or conjugate cholesterol, bilirubin, bile salts and other substances, and would be possible to dissolve and contain these substances in a stable condition in bile. Moreover, mucoprotein could also have the same role in the stability of thes substances in bile. Most of gallstones except cholesterin- and bilirubinstone contained proteins, which were presumably the conjugated protein such as albumin, fibrin or mucin conjugated with bilirubin. The author supposes that these proteins in gallstone are Fraction-II. Therefore, it might be sure that Fraction-II. in bile not only have important effects upon the colloid-chemical stability of bile, but also Fraction-II. themselves could be constituents of gallstones.
(author's abstract)

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