Bilirubin Chemistry and Metabolism; Harmful and Protective Aspects

Author(s): Libor Vitek, J. Donald Ostrow

Journal Name: Current Pharmaceutical Design

Volume 15 , Issue 25 , 2009

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Unconjugated bilirubin (UCB), the principal mammalian bile pigment, is the end product of heme catabolism. Both belong to the superfamily of tetrapyrrolic compounds that serve multiple biological functions in animals and plants. Its six internal hydrogen bonds give UCB a unique structure responsible for its physico-chemical properties and biological effects. Like many weakly-polar, poorly-soluble compounds, UCB is transported in blood tightly bound to albumin, with less than 0.01% of total bilirubin circulating in an unbound form (free bilirubin, Bf). This fraction governs the diffusion of UCB into tissues, and therefore Bf is responsible for both its beneficial and toxic effects on cells. Although, UCB was long thought to be a non-functional waste product, recent studies have shown that the antioxidant effects of mildly elevated serum bilirubin levels, as well as activation of heme oxygenase, may protect against diseases associated with oxidative stress, such as atherosclerosis. By contrast, markedly elevated serum UCB levels may cause severe neurological damage, especially in neonates. The regulation of cellular UCB content, by its conjugation, oxidation, and export, are, therefore of paramount importance to cellular health.

Keywords: Bilirubin, bile pigments, bilirubin chemistry, bilirubin structure, heme oxygenase, oxidative stress, carbon monoxide, heme catabolic pathway

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Article Details

Year: 2009
Published on: 01 March, 2012
Page: [2869 - 2883]
Pages: 15
DOI: 10.2174/138161209789058237
Price: $65

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