Bilirubin

Structural formula
deprotonated form of bilirubin (under physiological conditions)
General
Surname	Bilirubin
other names	3- (2 - ((3- (2-carboxyethyl) -4-methyl-5 - (( E ) - (3-methyl-5-oxo-4-vinyl-1 H -pyrrole-2 (5 H ) - ylidene) methyl) -1 H -pyrrole-2-yl) methyl) -4-methyl-5 - (( e ) - (4-methyl-5-oxo-3-vinyl-1 H -pyrrole-2 (5 H ) -ylidene) methyl) -1 H -pyrrol-3-yl) propanoic acid
Molecular formula	C 33 H 36 N 4 O 6
Brief description	red solid
External identifiers / databases
CAS number 635-65-4 18422-02-1 (calcium salt) 93891-87-3 (di hydrochloride ) PubChem 5280352 Wikidata Q104219
properties
Molar mass	584.66 g mol −1
Physical state	firmly
solubility	almost insoluble in water moderately in ethanol and diethyl ether good in benzene , chloroform , chlorobenzene , carbon disulfide , acids and bases
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

The bilirubin ( Latin bilis "bile" and ruber "red") is a yellow breakdown product of heme stake of the red blood pigment hemoglobin and thus a bile pigment . The pigment occurs naturally not only in animals, but also in plants; It was first detected in the seeds of tree strelitzia in 2009 . Bilirubin was first successfully synthesized in 1942 by Hans Fischer .

metabolism

Red blood cells live for about 120 days, after which they are broken down in the liver and spleen . The yellowish substance bilirubin is formed from heme b , the red blood pigment that is produced when it is broken down. About 300 mg of bilirubin are produced daily in the human organism, around 70 percent of which comes from the breakdown of aged erythrocytes (red blood cells), the rest from the metabolism of other hemoproteins, excess hemoglobin or from precursor cells in the bone marrow. Bilirubin is good in fat ( lipophilic ), but very poorly soluble in water. In order to be transported in the blood, it must therefore be linked to albumin , a blood protein, through a loose, non-covalent bond and is then called unconjugated bilirubin (synonym: indirect bilirubin). Bilirubin can also form a covalent, i.e. firm bond with albumin. This form is then known as delta bilirubin.

Unconjugated bilirubin is then coupled ( conjugated ) to glucuronic acid in the liver by the enzyme UDP-glucuronosyltransferase and is called "conjugated bilirubin" in this water-soluble form. Conjugated bilirubin and delta bilirubin are collectively referred to as "direct bilirubin". Direct bilirubin can be excreted into the intestine with the bile . In the intestine, conjugated bilirubin is then through the intermediate stages Mesobilirubinogen and stercobilinogen ( latin stercus "chair") to stercobilin transferred. About 20 percent of the bilirubin released into the intestine is subject to an enterohepatic cycle as urobilinogen and stercobilinogen , so it is absorbed again. The majority, however, is excreted with the stool. A small part of the absorbed urobilinogen is eliminated via the urinary tract . In the case of liver dysfunction, these products are increasingly excreted in the urine ( bilirubinuria ). High concentrations of bilirubin are toxic.

Causes of abnormal bilirubin levels

The normal value of total bilirubin in serum is below 21 µ mol / l (1.2 mg / dl). If the serum bilirubin level is increased (hyperbilirubinemia), jaundice (deposit of bilirubin in the skin, Greek jaundice) occurs, whereby from a double normal value first the sclera (the white skin of the eyes) and later the rest of the skin turn yellow. With pronounced hyperbilirubinemia, almost all organs turn yellow due to the massive deposition in the tissue . Depending on the cause and type of the increased bilirubin, there are also other symptoms, such as skin itching (Latin pruritus).

In Meulengracht's disease , jaundice can occur with almost no disease value due to a breakdown of bilirubin. The Rotor syndrome and Dubin-Johnson syndrome is a rare hereditary disorder of bilirubin metabolism.

A cholestasis (backflow of bile by gallstones or other obstructions in or on the bile ducts) can lead to an increase in the Bilirubinwerts.

In newborns , an increased bilirubin level is normal because the fetal hemoglobin is broken down, the liver is not yet working fully and there is not enough excretion (by the 30th week of pregnancy, the activity of the enzyme glucuronyltransferase, which catalyzes the conversion into direct bilirubin, reaches 0 , 1 percent of the adult value, at the due date approx. 1 percent). Newborn jaundice occurs in around 60 percent . Due to the not yet fully developed blood-brain barrier , if age- and weight-dependent limit values ​​are exceeded, developmental disorders due to kernicterus (deposits in the basal ganglia in the cerebrum ) can occur. The bilirubin deposited in the skin can be converted to water-soluble lumirubin by means of phototherapy and thus excreted.

But the breakdown of the ingredients of drugs in the liver can also lead to increases in bilirubin levels.

literature

• Gerd Herold: Internal Medicine . 2005.
• Georg Löffler, Petro E. Petrides, Peter C. Heinrich: Biochemistry & Pathobiochemistry. 8th edition. Springer-Verlag, Heidelberg 2007, ISBN 978-3-540-32680-9 .
• Stefan Silbernagl, Agamemnon Despopoulos: Color Atlas of Physiology. 6th edition. Thieme, 2009, ISBN 978-3-13-545006-3 .

Web links

Wikibooks: Biochemistry and Pathobiochemistry: Porphyrin Breakdown  - Learning and Teaching Materials

Individual evidence

1. ↑ ^{a b} data sheet bilirubin from Sigma-Aldrich , accessed on May 25, 2011 ( PDF ).
2. ↑ ^{a b c} Entry on bilirubin. In: Römpp Online . Georg Thieme Verlag, accessed on May 29, 2014.
3. ↑ C. Pirone et al. a .: Animal Pigment Bilirubin Discovered in Plants. In: J. Am. Chem. Soc. Volume 131 (8), 2009, p. 2830 f. doi: 10.1021 / ja809065g .
4. ^ Henryk Dancygier: Clinical hepatology: Basics, diagnostics and therapy of hepatobiliary diseases . Springer-Verlag, March 8, 2013, ISBN 978-3-642-55902-0 , p. 347.
5. ↑ Karen Marc Dante, Robert M. Kliegman: Nelson Essentials of Pediatrics . Elsevier Health Sciences, February 25, 2014, ISBN 978-0-323-22698-1 , p. 219.
6. ↑ Gabriele Halwachs-Baumann: Laboratory Medicine. Clinic - practice - case studies. Springer-Verlag, Vienna 2006, ISBN 3-211-25291-6 .
7. ↑ Melanie Königshoff, Timo Brandenburger: Short textbook biochemistry. 2nd Edition. Georg-Thieme-Verlag, Stuttgart / New York 2007, ISBN 978-3-13-136412-8 .
8. ↑ Guido Majno: Cells, Tissues, and Disease. Oxford University Press, 2004, ISBN 978-0-19-974892-1 , p. 118.
9. ↑ Hilmar Burchardi: The intensive care medicine. Springer-Verlag, 2011, ISBN 978-3-642-16929-8 , p. 568 ( limited preview in the Google book search).
10. ↑ C. Bührer et al. a .: Hyperbilirubinemia of the newborn - diagnosis and therapy. AWMF guideline. AWMF, Düsseldorf 2015.

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !