- A yellow bile pigment found as sodium bilirubinate (soluble), or as an insoluble calcium salt in gallstones; formed from hemoglobin during normal and abnormal destruction of erythrocytes by the reticuloendothelial system; a bilin with substituents on the 2, 3, 7, 8, 12, 13, 17, and 18 carbon atoms and with oxygens on carbons 1 and 19. Excess b. is associated with jaundice. [bili- + L. ruber, red]- conjugated b. SYN: direct reacting b..- delta b. the fraction of b. covalently bound to albumin; in conventional methods it is measured as part of conjugated b.. Because of its covalent bond during the recovery phase of hepatocellular jaundice it may persist in the blood for a week or more after urine clears.- direct reacting b. the fraction of serum b. which has been conjugated with glucuronic acid in the liver cell to form b. diglucuronide; so called because it reacts directly with the Ehrlich diazo reagent; increased levels are found in hepatobiliary diseases, especially of the obstructive variety. SYN: conjugated b..- indirect reacting b. the fraction of serum b. which has not been conjugated with glucuronic acid in the liver cell; so called because it reacts with the Ehrlich diazo reagent only when alcohol is added; increased levels are found in hepatic disease and hemolytic conditions. SYN: unconjugated b..- b. UDPglucuronyltransferase (gloo-koo′ron-il-trans′fer-as) an enzyme that catalyzes the reaction of UDPglucuronate and b. forming UDP and b.-glucuronoside; a deficiency of this enzyme is associated with Crigler-Najjar syndrome.- unconjugated b. SYN: indirect reacting b..
* * *bil·i·ru·bin .bil-i-'rü-bən, 'bil-i-. n a reddish yellow pigment C33H36N4O6 that occurs esp. in bile and blood and causes jaundice if accumulated in excess
* * *n.
* * *bil·i·ru·bin (bil″ĭ-rooґbin) [bili- + ruber] a yellow bile pigment that is a breakdown product of heme mainly formed from the degradation of erythrocyte hemoglobin in reticuloendothelial cells; it is also formed by breakdown of other heme pigments, such as cytochromes. Bilirubin normally circulates in plasma as a complex with albumin, and is taken up by the liver cells and conjugated to form water-soluble bilirubin diglucuronide for excretion in the bile. In patients with cholestasis, this latter form accumulates in the blood and tissues and is excreted in the urine. (Unconjugated bilirubin is not excreted in the urine.) High concentrations of bilirubin may result in jaundice. bilirubinic adj
Medical dictionary. 2011.