bilirubin

Physiology

,Bilirubin is a waste product of heme metabolism, produced largely in the spleen where senescent erythrocytes are phagocytosed. However, it is also produced in the brain where it may serve a constituent role as an antioxidant.

Bilirubin is formed from heme by sequential actions of heme oxygease in association with cyt P450 reductase & bilirubin reductase

                    heme oxygenase
                  cyt P450 reductase
heme[Fe+2] + O2   ------------------>   biliverdin + CO + Fe+2
+ NADPH + H+                            + NADP+  + H2O

                biliverdin reductase
    biliverdin  -------------------->   bilirubin + NADP+
  + NADPH + H+

Biliverdin reductase rapidly reduces biliverdin to bilirubin.

Bilirubin binds non-covalently to albumin (unconjugated bilirubin) for transport to the liver, where it is conjugated with glucuronic acid (conjugated bilirubin), then excreted in the bile. In certain conditions, bilirubin may also bind covalently to albumin to form delta-bilirubin.

Bilirubin has the capacity to reduce 10,000 higher fold concentrations of H2O2 through the biliverdin reductase cycle

Laboratory

• bilirubin in specimen
  • bilirubin in skin
  • bilirubin in stone
  • bilirubin in body fluid
    • bilirubin in amniotic fluid
    • bilirubin in CSF
    • bilirubin in pericardial fluid
    • bilirubin in peritoneal fluid
    • bilirubin in serum
    • bilirubin in stool
    • bilirubin in synovial fluid
    • bilirubin in urine
• bilirubin direct in body fluid
  • bilirubin direct in blood
  • bilirubin direct in serum/plasma
  • bilirubin direct in peritoneal fluid
  • bilirubin direct in pleural fluid
• bilirubin indirect in body fluid
  • bilirubin indirect in blood
  • bilirubin indirect in peritoneal fluid
• bilirubin conjugated in body fluid
  • bilirubin conjugated in dialysis fluid
  • bilirubin conjugated in peritoneal fluid
  • bilirubin conjugated in serum
• bilirubin unconjugated in serum
• bilirubin crystals in urine

More general terms

• heme metabolite
• pigment

More specific terms

• bilirubin diglucuronide; conjugated bilirubin; direct bilirubin
• delta bilirubin

Additional terms

• bilirubin conjugated in serum
• bilirubin in urine (Ictotest)
• bilirubin metabolism, inborn error
• bilirubin unconjugated in serum (indirect bilirubin)
• heme catabolism

Database

• PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=250
• PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=5315454
• PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=457804
• PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=5280352
• PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=8235