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

Abstract

A method was developed to extract quantitatively the bilirubins from bile, urine, serum, stool, and preparations from liver with a chloroform-ethanol mixture at pH 1.8 in the presence of ascorbic acid and NaCl. Extracted pigment was submitted to thin-layer chromatography, and the separated bilirubins were either immediately eluted and determined spectrophotometrically or individually converted to ethyl anthranilate azo derivatives for thin-layer chromatographic analysis of each isolated pigment band. Bilirubins in duodenal bile of eight healthy adults comprised 1.5 ± 1.3% unconjugated bilirubin-IXα, 69 ± 6% bilirubin diglucuronide, and 16 ± 4% bilirubin monoglucuronides. Mixed diconjugates containing one glucuronosyl moiety and either one xylosyl or one glucosyl group amounted to 10 ± 3%. Most samples (6 of 8) contained trace amounts (0.6 ± 0.6%) of unconjugated bilirubin-IXβ, in agreement with nearly exclusive cleavage of heme at the α-meso position. The composition of the bilirubins in bile was normal in 6 patients with cholesterol gallstones, 4 with chronic hepatitis, and 3 with hemolysis. In duodenal bile of individuals with Gilbert's syndrome (n = 10), the concentration of bttirubin conjugates was comparable to that in healthy adults, but the proportion of bilirubin diglucuronides (52 ± 8%) was decreased. The concentration of unconjugated bilirubin-IXα showed a fair positive correlation with that of bilirubin monoglucuronide and was increased in half of the patients with Gilbert's syndrome.