Role of chloride and intracellular pH on the activity of the rat hepatocyte organic anion transporter

J Clin Invest. 1991 May;87(5):1496-502. doi: 10.1172/JCI115159.

Abstract

Previous studies in cultured rat hepatocytes revealed that initial uptake of sulfobromophthalein (BSP) was markedly reduced upon removal of Cl- from the medium. In the present study, unidirectional Cl- gradients were established in short-term cultured rat hepatocytes and their effect on BSP uptake was determined. These investigations revealed that BSP uptake requires external Cl- and is not stimulated by unidirectional Cl- gradients, suggesting that BSP transport is not coupled to Cl- transport. In contrast, BSP transport is stimulated by an inside-to-outside OH- gradient, consistent with OH- exchange or H+ cotransport. As the presence of Cl- is essential for but not directly coupled to BSP transport, binding of 35S-BSP to hepatocytes was determined at 4 degrees C. This revealed an approximately 10-fold higher affinity of cells for BSP in the presence as compared to the absence of Cl- (Ka = 3.2 +/- 0.8 vs. 0.42 +/- 0.09 microM-1; P less than 0.02). Affinity of BSP for albumin was Cl(-)-independent, and was approximately 10% of its affinity for cells in the presence of Cl-. These results indicate that extracellular Cl- modulates the affinity of BSP for its hepatocyte transporter.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Anion Transport Proteins
  • Biological Transport
  • Carrier Proteins / metabolism*
  • Cells, Cultured
  • Chlorides / metabolism*
  • Hydrogen-Ion Concentration
  • Liver / metabolism*
  • Male
  • Protein Binding
  • Rats
  • Rats, Inbred Strains
  • Serum Albumin, Bovine / metabolism
  • Sulfobromophthalein / pharmacokinetics

Substances

  • Anion Transport Proteins
  • Carrier Proteins
  • Chlorides
  • Sulfobromophthalein
  • Serum Albumin, Bovine