The glutathione S-transferases: their role in the transport of organic anions from blood to bile.

The glutathione transferases are abundant multifunctional proteins of liver cytosol. In addition to their catalytic activity, they also bind as nonsubstrate ligands a variety of compounds that contain a hydrophobic nucleus. Included among these ligands are organic anions such as bilirubin. The abundance of these proteins and their avid binding of bilirubin and its conjugates have encouraged investigation into their potential role in hepatic transport and metabolism of organic anions. These studies suggest that the glutathione transferases perform a binding function within the cell analogous to that of albumin extracellularly. Although there is no evidence that these proteins are responsible for recognition and uptake of organic anions from the vascular space, they influence net uptake by binding these substances within the cell, reducing their efflux into plasma. The relationship of intracellular binding of bilirubin to the conjugation and excretory mechanisms is the subject of investigation at the present time.