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

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 It might be outdated or ideologically biased.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 ?
Moreover, CPB time had a direct and significant relationship with the mean direct and indirect bilirubin and AST (P<0.05), whereas it had no significant correlation with the changes in the ALT and ALP levels.
* Elevated serum indirect bilirubin with increased reticulocyte count is indicative of increased hemolysis seen with ABO/Rh incompatibility and red blood cell abnormalities.
It requires immediate hospitalization.4,5 In patients suspected with viral hepatitis along with unexplained anaemia, intravascular haemolysis, high direct and indirect bilirubin levels require prompt medical attention.
Indirect bilirubin 0.23[+ or -]0.04 1.0[+ or -]0.13 (*) (mg/dl) (**) Significant (P< 0.1) (*) Significant (P< 0.5) NS - Non-significant Table 3: Comparative hemato-biochemical values in goats treated for babesiosis S.
In our case group, we found a significantly lower level of haemoglobin (Table 1) in our case group with raised values of indirect bilirubin indicating increased haemolysis in partial HELLP also.
Total and indirect bilirubin levels were measured at the beginning of treatment and then 12, 24, 36, and 48 hours later.
When the elevation is predominantly indirect bilirubin, consider drug cholestasis or when very elevated, a biliary obstruction, including the possibility of a biliary or pancreatic neoplasm.
In each subject, after an overnight fast, plasma concentrations of total and direct-reacting bilirubin were determined by a diazo method at least three times within 6 months before the study; indirect bilirubin was calculated as total minus direct bilirubin.
Routine blood investigations (Total Count: 7000 cells/cu.mm; Total Bilirubin: 1 mg/dL; Indirect bilirubin: 0.2 mg/dL; Direct bilirubin: 0.8 mg/dL; Total Protein: 8 g/dL; Albumin 5 g/dL) and lipid profile (Total Cholesterol: 160 mg/dL; LDL: 90 mg/dL; HDL: 45 mg/dL) were within normal limits.
Both direct bilirubin (5.3mg/dl) and indirect bilirubin (6.6 mg/dl) were also found to be elevated.
Liver Function Tests showed a total Bilirubin of 11.27mg/dl, with Direct Bilirubin as 9.76 mg/dl and Indirect Bilirubin as 1.51mg/dl with normal liver enzymes.
Serum biochemistry revealed elevated bilirubin level (9.4mg/dl) against normal level of 0.1-0.5 mg/dl, direct bilirubin level (4mg/dl) and indirect bilirubin level (5.4mg/dl) were also found to be elevated.