Bilirubin


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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

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.

bilirubin

[‚bil·ə′rü·bən]
(biochemistry)
C33H36N4O6 An orange, crystalline pigment occurring in bile; the major metabolic breakdown product of heme.
References in periodicals archive ?
Bilirubin industry import/export consumption, supply and demand figures and cost price and production value gross margins are also provided.
Increased serum bilirubin level without jaundice in patients with monoclonal gammopathy.
Hepatic crisis is another common complication of sickle cell disease, characterized by short disease duration (2-3 weeks) with a serum bilirubin level that seldom exceeds 15 mg/dL (1).
The Clinical and Laboratory Standards Institute has stated that many of the historical confirmatory chemical urinalysis tests such as the sulfosalicylic acid (SSA) test for protein, the tablet test for ketones, and the tablet test for bilirubin may not be relevant to current laboratory practice.
Conjugated bilirubin is gold in colour and when mixed with bile is responsible for the colouration of stools and urine (England, 2010).
Bilirubin makes sense as a protective agent because of its anti-oxidant, anti-inflammatory and anti-proliferative effects.
The form of bilirubin most toxic to the developing neonatal brain is freely circulating (unconjugated) bilirubin.
From the 17th week of gestation her bilirubin level was stable and remained within the normal range.
Jaundice occurs when the blood cannot cope with all the bilirubin being produced
EBV hepatitis usually presents with a two to three-fold elevation in transaminases, elevation of LDH, alkaline phosphatase and bilirubin levels.
Bu calismada farkli nedenlere bagli olarak ortaya cikabilen uzamis sarilik olgularinda etyolojik nedenlerin belirlenmesi, etyoloji ile bilirubin duzeyleri arasinda bir iliski olup olmadigini saptanmasi amaclandi.
It would be helpful if a separate section were included for the evaluation of patients with elevated LFTs at baseline," the firms comments state In particular, Wyeth requested that that section "emphasize the need to differentiate the presence of direct bilirubin elevations from indirect bilirubin elevations, by obtaining both total and direct bilirubin levels.