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

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 ?
The total and conjugated bilirubin levels were high in all the groups and were not significantly different (p>0.
Unfortunately, as highlighted by this case, practitioners face a number of challenges in interpreting newborn conjugated bilirubin concentrations correctly.
A child experiencing biliary atresia may display prolonged jaundice, raised conjugated bilirubin levels, dark urine and pale stools as a result of loss of bile pigment (Hockenberry and Wilson, 2007).
Abnormally high levels of serum conjugated bilirubin will exceed the ability of the kidneys to handle them, and can be detected in the urine on dipstick and visually: the urine becomes very dark ("tea"-coloured).
The biochemical parameters evaluated at the time of diagnosis were aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin, unconjugated bilirubin, conjugated bilirubin, lactate dehydrogenase, hemoglobin, and hematocrit.
In 2005, Nauti et al (2) reported that serum from 3 patients with a monoclonal protein interfered with the Beckman Coulter AU2700 (Beckman Coulter, Brea, California; formerly Olympus Diagnostics, Melville, New York) conjugated bilirubin assay and produced falsely increased values, exceeding the total bilirubin concentration.
This will include measurements of total and conjugated bilirubin, urine screening, assessment for G6PD deficiency if appropriate, ensuring the Guthrie test has been performed to exclude congenital hypothyroidism, (6) and investigations to determine other possible causes.
Conjugated bilirubin is non-toxic bilirubin that has been detached from albumin, become conjugated with glucuronic acid, and rendered water-soluble.
An increase in conjugated bilirubin suggests decreased secretion or bile duct obstruction.
d] = 16 nmol/L), it binds ditaurobilirubin, a model for conjugated bilirubin (17), with a [K.
A blood test is performed and Kyle is found to have a high conjugated bilirubin level.