[Hepatic metabolism and transport of bilirubin and other organic anions].
Most of bilirubin, bile acids and other organic anions are preferentially taken up by the liver and excreted into bile. Recently many transporters on the sinusoidal and canalicular membranes of the hepatocytes have been reported for each ligand. complementary DNA was cloned for human Na+/taurocholate cotransporting polypeptide (NTCP) which mediates sodium dependent secondary active hepatic uptake of bile acids. For the hepatic uptake of non-bile acid-organic anions such as bilirubin, at least 4 transporters are postulated, i.e., bilirubin/BSP binding protein (BBBP), organic anion binding protein (OABP), bilitranslocase, and organic anion transporting polypeptide (OATP). In the hepatocytes, bilirubin is glucuronidated in the endoplasmic reticulum. The gene for UDP-glucuronosyltransferase (UGT) 1 family has been elucidated and differential splicing from several exons 1 (A to J) results in forming isozymes of UGT 1 including bilirubin UGT. At the canalicular membranes, two main ATP-dependent organic anion transporters have been reported, i.e., canalicular bile salt transporter (cBST) for bile acids and canalicular multispecific organic anion transporter (cMOAT) for non-bile acid organic anions. Recently multidrug resistance protein (MRP) is reported closely related to or identical to cMOAT. These canalicular ATP-dependent transporters are called ABC (ATP-binding cassette) transporters.
Adachi
Y
Y
Second Department of Internal Medicine, Kinki University School of Medicine.
Kamisako
T
T
Okuyama
Y
Y
Miya
H
H
D000818:Animals; D027321:Anion Transport Proteins; D001647:Bile Acids and Salts / Q000378:metabolism; D001663:Bilirubin / Q000378:metabolism*; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology; D005227:Fatty Acids / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000235:genetics / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D011453:Prostaglandins / Q000378:metabolism
D027321:Anion Transport Proteins; D001647:Bile Acids and Salts; D002352:Carrier Proteins; D005227:Fatty Acids; D011453:Prostaglandins; D014453:Glucuronosyltransferase; D005978:Glutathione; D001663:Bilirubin