Bilirubin

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Related to Conjugated bilirubin: Unconjugated bilirubin

Bilirubin

The predominant orange pigment of bile. It is the major metabolic breakdown product of heme, the prosthetic group of hemoglobin in red blood cells, and other chromoproteins such as myoglobin, cytochrome, and catalase. The breakdown of hemoglobin from the old red cells takes place at a rapid rate in the reticuloendothelial cells of the liver, spleen, and bone marrow. The steps in this breakdown process include denaturation and removal of the protein globin, oxidation and opening of the tetrapyrrole ring, and the removal of iron to form the green pigment biliverdin, which is then reduced to bilirubin by the addition of hydrogen. The formed bilirubin is transported to the liver, probably bound to albumin, where it is conjugated into water-soluble mono- and diglucuronides and to a lesser extent with sulfate. See Liver

In mammalian bile essentially all of the bilirubin is present as a glucuronide conjugate. Bilirubin glucuronide is passed through the liver cells into the bile caniculi and then into the intestine. The bacterial flora further reduces the bilirubin to colorless urobilinogen. Most of the urobilinogen is either reduced to stercobilinogen or oxidized to urobilin. These two compounds are then converted to stercobilin, which is excreted in the feces and gives the stool its brown color. See Hemoglobin

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Bilirubin

 

C33H36O6N4, a bile pigment; molecular mass 584.68. Brown crystals. Bilirubin is an intermediate product of the decomposition of hemoglobin that takes place in the macrophages of the spleen, liver, and bone marrow. It is formed by the enzymatic reduction of biliverdin. It is present in small quantities in the plasma of vertebrate animals and man (0.2–1.4 mg percent in a healthy person). When the outflow of bile is made difficult (obstruction of the bile ducts), and in some liver diseases, the bilirubin concentration increases in the blood (causing jaundice), and it appears in the urine. Hence, the presence of bilirubin in blood or urine is a diagnostic test.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

bilirubin

[‚bil·ə′rü·bən]
(biochemistry)
C33H36N4O6 An orange, crystalline pigment occurring in bile; the major metabolic breakdown product of heme.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The incidence of immunoglobulin interfering with the Olympus conjugated bilirubin assay appears to be very low.
Conjugated bilirubin is water soluble and therefore maybe detected in the urinalysis, while unconjugated bilirubin, insoluble, cannot pass through the renal glomerulus and cannot be detected in the test [12].
Cholestasis can also be assessed by using serum biochemical markers such as liver function tests (total and conjugated bilirubin) and liver enzymes (alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and gamma glutamyl transferase (GGT)).
Surprisingly, we found that conjugated bilirubin slightly prolonged aPTT in citrated plasma, and more prominent prolongation was observed in heparinized samples.
Furthermore, the elevation in total and conjugated bilirubin levels observed in the present study indicates posthepatic toxicity possibly caused by an interruption to the drainage of bile in the biliary system following exposure to 2,5-HD.
McIntosh and Stenson (2008) outline that conjugated bilirubin is excreted into bile and then transported to the small intestine where it is then broken down by bacteria in the intestine.
Direct bilirubin is a measure of the amount of conjugated bilirubin, and is determined directly.
Patients who were found to have a conjugated bilirubin level above 50 [micro]mol/L were classified as the cholestasis group.
The term cholestasis refers to a group of disorders associated with bilirubin excretion and accompanied by a rise in serum conjugated bilirubin levels and often, bile salts and phospholipids.
Laboratory investigations revealed evidence of obstructive jaundice with serum total bilirubin of 16 mg/dL and conjugated bilirubin 8.2 mg/dL.
The complex that is secreted in bile is called conjugated bilirubin. The conjugated bilirubin is eliminated in the feces.