Analysis of bilirubins in biological fluids by extraction and thin-layer chromatography of the intact tetrapyrroles: application to bile of patients with Gilbert's syndrome, hemolysis, or cholelithiasis

Isomers of bilirubin glucuronide in serum and bile before and after relief of common duct obstruction

Isomers of bilirubin glucuronide with the bilirubin acyl group attached to the C1-, C2-, C3- and C4-positions of the glucuronyl residue are present in bile of patients with extrahepatic cholestasis, whereas in normal bile only C1-isomers are found. In the present study, these bilirubin glucuronide isomers, and the fractions of unconjugated bilirubin, and bilirubin mono- and diconjugates were determined in serum and bile of 8 patients before and after relief of common duct obstruction by endoscopic papillotomy. Before papillotomy we found 39.6% C1-isomers (median value), 22.2% C2-isomers, 19.3% C3-isomers and 11.4% C4-isomers in the bile. The values in serum before papillotomy were comparable. Twenty-four hours after papillotomy, the level of C1-isomers in bile increased significantly to 56.3% (P less than 0.05) with a concomitant decrease of the non-C1-isomers. In contrast, in serum the isomers of bilirubin glucuronide did not change significantly at 24 h after papillotomy. Before papillotomy, the fraction of unconjugated bilirubin in bile was 3.6% of the total, with 15.8% bilirubin monoconjugates and 75.5% bilirubin disconjugates. After papillotomy, unconjugated bilirubin decreased to 1.6% (n.s.) and bilirubin monoconjugates to 11.9% (n.s.), while bilirubin diconjugates increased to 86.1% (P less than 0.05). In serum, the elevated fractions of bilirubin diconjugates and monoconjugates decreased from 38.4 to 32.2% (P less than 0.05) and from 29.6 to 23.4% (n.s.), respectively. In parallel, the fraction of unconjugated bilirubin in serum increased from 24.1 to 37.0% (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of gallbladder mucin-bilirubin complex in human cholesterol gallstone matrix. Effects of reducing agents on in vitro dissolution of matrix and intact gallstones

The goals of this study were to isolate and characterize the nonlipid matrix of human cholesterol gallstones. The lipid portion of gallstones was dissolved in ethanol/ether, leaving an insoluble, granular, brown-black matrix that constituted 12.5% of solitary large stones and 3.5% of multiple small stones. The matrix was partially solubilized by sonication and studied by exclusion gel chromatography and density gradient ultracentrifugation. On Sepharose 2B column chromatography, bile pigment eluted with glycoprotein in the void volume, suggesting the presence of a high molecular weight complex (Mr greater than 2 X 10(6)). The identity of mucin in this complex was confirmed by its typical buoyant density during ultracentrifugation. The major bile pigments in the matrix were identified as bilirubin (84%) and bilirubin monoglucuronide (15%) by thin-layer chromatography. Because of their ability to solubilize mucin-type glycoproteins, we tested the ability of the reducing agents 2-mercaptoethanol (2ME) and N-acetylcysteine (NAcCys) to solubilize gallstone matrix. Both reducing agents caused a two- to threefold enhancement of matrix dissolution after 4 d compared to aqueous buffer alone (P less than 0.01). Sepharose 2B chromatography revealed that 2ME released a high molecular weight mucin-bilirubin complex as well as unbound pigment from the insoluble matrix. We also tested the effect of reducing agents on dissolution of matched cholesterol gallstones by monooctanoin, a cholesterol solvent. Both 2ME and NAcCys significantly accelerated gallstone dissolution in monooctanoin. Matched human cholesterol stones (n = 10) incubated for 4 d in monooctanoin plus either 2ME or NAcCys (1 M final concentration) weighed approximately half as much (P less than 0.01 for each) as stones incubated in monooctanoin alone. This study describes, for the first time, the isolation of a bilirubin-mucin complex in the insoluble matrix of human cholesterol gallstones. The ability of reducing agents to dissolve the matrix and thereby accelerate gallstone dissolution by monooctanoin in vitro may be relevant to gallstone dissolution in humans.

Urinary excretion of isomers of biliverdin after destruction in vivo of haemoproteins and haemin

The amount and isomeric composition of urinary biliverdin in rabbits were analysed by h.p.l.c. Physiological values were maintained after the injection of haemin. On the other hand, when haemoglobins from several mammalian species were injected into rabbits, the excretion of biliverdin-IX alpha and biliverdin-IX beta were increased 6-18-fold and 32-66-fold respectively over physiological excretion. Injection of myoglobin resulted in a 44-fold increase in excretion of the IX alpha-isomer. Coupled oxidation with ascorbate of haemoglobin and myoglobin by oxygen produced mainly the IX alpha- and IX beta-isomers from haemoglobin and the IX alpha-isomer from myoglobin. The destruction of part of the haem from injected haemoproteins by non-enzymic chemical degradation would account for the observed respective increases in the excretion of biliverdin isomers. The excretion of biliverdin isomers after the injection of phenylhydrazine into rabbits was similar to that after the injection of haemoglobin.

Effects of ioglycamide on the hepatic transport of bilirubin and its mono- and diconjugates in the rat

Bilirubin seems to share the biliary excretion pathway with other organic anions, but not with bile acids. We studied the effects of the organic anion ioglycamide, an iodinated contrast agent, on bilirubin metabolism in Wistar rats. This compound does not undergo conjugation and is characterized by a maximal biliary secretory rate (Tm). The results show that in spite of producing a 3-fold increase in bile flow, ioglycamide excretion under Tm conditions decreased the output of unconjugated bilirubin and its monoconjugate by approximately 90%. Diconjugated bilirubin decreased by only 50% and became by far the predominant pigment in bile (86.5 +/- 6.0% of total pigment vs. 61.0 +/- 4.0% in basal conditions, n = 12). Unconjugated and monoconjugated bilirubins changed in parallel suggesting that the former arises from the monoconjugates. In serum, diconjugated bilirubin augmented from trace amounts to 1.15 +/- 0.17 mumole per liter. Total conjugated pigments in serum increased from 5 to 85% of total bilirubin. Bile acid output remained unchanged. Pretreatment of rats with ioglycamide altered neither the activity of bilirubin UDP-glucuronyltransferase nor the ratio of diconjugate to monoconjugate formed at both low (25 microM) and high (164 microM) bilirubin concentrations. The observed biological effects of ioglycamide were dose-dependent and fully reversible. We suggest that ioglycamide interferes with the excretion of conjugated bilirubins ("bilirubinostasis"). The monoconjugates retained in the hepatocyte might then undergo more efficient transformation to diconjugates, the latter thus becoming the most important bile pigments in serum and bile.

An unusual case of Crigler-Najjar disease in the adult. Classification into types I and II revisited

We present the case of a 25-year-old man with Crigler-Najjar disease who had since birth a marked unconjugated hyperbilirubinemia without bilirubin overproduction, without any neurological involvement and in whom phenobarbital administration failed to produce any effect. Analysis of his biliary bile pigments on two occasions showed (i) a decrease excretion of bilirubin, as indirectly suggested by a high ratio of biliary bile acids over total bilirubin; (ii) an increase in unconjugated bilirubin IX alpha quantitated by thin-layer chromatography (TLC) following alkaline methanolysis and by direct extraction and TLC of the tetrapyrroles; (iii) a high proportion of bilirubin monoconjugates whereas the excretion of diconjugates was very low. Classification of the present patient into Crigler-Najjar disease type I or II was not possible. The most striking and practical difference among the various cases of Crigler-Najjar disease remains the response to phenobarbital. Among cases of Crigler-Najjar disease which respond to enzyme induction and Gilbert's syndrome, the continuous spectrum suggests a common defect.

The etiology of pigment gallstones

Pigment gallstones are of two major types, black and earthy brown, each consisting of calcium salts of bilirubin and other anions, along with an unmeasured residue that is largely mucin glycoproteins. Studies in model systems indicate that the small proportion of unconjugated bilirubin in bile is solubilized by bile salts and that the ionized bilirubin is more soluble than the protonated diacid. Solubility is decreased by added lecithin but is unaffected by cholesterol. At the pH of bile, unconjugated bilirubin exists mainly as a monoanion with sufficient solubility in mixed micelles not to precipitate, were it not for the presence of calcium, which forms highly insoluble salts with unconjugated bilirubin anions. Supersaturation of bile with calcium bilirubinates is inhibited by bile salts, which bind calcium, reducing the activity of free calcium ions. When supersaturation occurs, usually due to increased concentrations of bilirubinate anion, nucleation may be initiated by binding of calcium bilirubinate to mucin glycoproteins in bile. In earthy brown stones, which form mainly in the bile ducts, the pigment is mostly calcium bilirubinate, combined with calcium palmitate. These components form due to hydrolysis, by enzymes in infecting bacteria, of conjugated bilirubin and lecithin, respectively. In black stones, which form mainly in the gallbladder, the pigment is mostly a highly cross-linked network polymer of bilirubin, which is insoluble in all solvents. Concomitant polymerization and oxidation of calcium bilirubinate probably occur in the solid state, after precipitation of the pigment due to hydrolysis of conjugated bilirubin by endogenous beta-glucuronidase from the biliary tract and/or liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitation of bilirubin conjugates with high-performance liquid chromatography in patients with low total serum bilirubin levels

Bilirubin mono- and diconjugates were determined by alkaline methanolysis and high-performance liquid chromatography (HPLC) in serum from patients with metastatic liver disease and liver cirrhosis. Conjugates could be detected and quantitated at normal or low total bilirubin levels. Comparison with serum alkaline phosphatase activity revealed that in cirrhosis bilirubin conjugates were sometimes detectable at normal or slightly elevated alkaline phosphatase activities. In patients with metastatic liver disease alkaline phosphatase activity was a more sensitive indicator. In normal controls and in patients with Gilbert's syndrome no bilirubin conjugates were detected whereas serum of patients with haemolysis contained conjugated bilirubin. Therefore HPLC appears to be an excellent method to diagnose Gilbert's syndrome. In liver cirrhosis HPLC is a useful liver function test.

Irreversible binding of conjugated bilirubin to albumin in cholestatic rats

A diazo-positive fraction of serum bilirubin that is irreversibly bound to albumin has been shown to accumulate in serum of patients with cholestasis. In the present study, a cholestatic animal model was used to determine the chemical nature of the bilirubin species involved in its formation. The data indicate that conjugated bilirubin is the precursor of "albumin-bound bilirubin" and that the presence or absence of light does not affect its formation. An albumin-bound bilirubin-complex indistinguishable from the complex detected in cholestatic sera from patients or in bile duct-ligated Sprague-Dawley rats can be formed in vitro in sera enriched in conjugated bilirubin at 37 degrees C, pH 7.4.