ABSTRACT
This review focuses on oatp, a rat liver protein that has been cloned on the basis
of its ability to transport organic anions such as bilirubin and sulfobromophthalein
(BSP). Although other proteins have been suggested as having bilirubin or BSP transport
activity, these data have primarily been indirect, and their cloning and expression
have not yet been accomplished. Although preliminary data suggest that organic anion
transporting polypeptide (oatp) accounts for a significant amount of BSP transport
into the hepatocyte, there is certainly the possibility that other transporters exist.
In addition, oatp appears to be a member of a new family of integral membrane transport
proteins that may have overlapping substrate specificities.
Organic anions such as bilirubin and sulfobromophthalein (BSP) circulate bound tightly
to albumin from which they are rapidly extracted by hepatocytes. This process of organic
anion uptake has been the subject of extensive investigation over many years. Although
details remain unresolved, much has been learned recently regarding the mechanisms
of organic anion transport. This article will examine the history and current status
of this field.
KEY WORDS
anion transport - oatp - BSP
