Role of multidrug resistance protein 2 (MRP2) in glutathione‐bimane efflux from Caco‐2 and rat renal proximal tubule cells

• Published in: British journal of pharmacology Vol. 134; no. 5; pp. 931 - 938
• Main Authors: Terlouw, Sylvie A, Masereeuw, Rosalinde, Van Den Broek, Petra H H, Notenboom, Sylvia, Russel, Frans G M
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.11.2001; Nature Publishing
• Subjects: Adenosine Triphosphate - pharmacology; Animals; ATP-Binding Cassette Transporters; Biological and medical sciences; Biological Transport - drug effects; Biological Transport - genetics; Caco-2 Cells; Carrier Proteins - genetics; Carrier Proteins - physiology; Cell physiology; Cells, Cultured; Dinitrochlorobenzene - pharmacology; Dose-Response Relationship, Drug; Fundamental and applied biological sciences. Psychology; Glutathione - chemistry; Glutathione - pharmacokinetics; glutathione conjugates; Humans; Kidney Tubules, Proximal - cytology; Kidney Tubules, Proximal - metabolism; Kidney Tubules, Proximal - ultrastructure; Leukotriene C4 - pharmacokinetics; Male; Membrane and intracellular transports; Membranes - drug effects; Membranes - metabolism; Microvilli - drug effects; Microvilli - metabolism; Molecular and cellular biology; monochlorobimane; Multidrug resistance protein 2; organic anions; Pyrazoles - chemistry; Rats; Rats, Mutant Strains; renal proximal tubular cells; Temperature; Time Factors; Human; Excretion; Rat; Digestive system; Gene product; Biological transport; Rodentia; Gut; Strain specificity; In vitro; Protein; Kidney; Vertebrata; Organic anion; Mammalia; Urinary system; Animal; Conjugated compound; Mechanism of action; Proximal tube; Glutathione
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0704284

The multidrug resistance protein 2 (MRP2) has been shown to play an important role in the transport of glutathione conjugates in the liver. Its importance in renal excretion, however, is still uncertain and other organic anion transporters may be involved. The objective of the present study was to characterize glutathione conjugate efflux from rat kidney proximal tubule cells (PTC), and to determine the contribution of Mrp2. We used isolated PTC in suspension, as well as grown to monolayer density. For comparison, transport characteristics were also determined in the human intestinal epithelial cell line Caco‐2, an established model to study MRP2‐mediated transport. The cells were loaded with monochlorobimane (MCB) at 10°C. MCB enters the cells by simple diffusion and is conjugated with glutathione to form the fluorescent glutathione‐bimane (GS‐B). In primary cultures of rat PTC, no indications for a transporter‐mediated mechanism were found. The efflux of GS‐B from Caco‐2 cells and freshly isolated PTC was time‐ and temperature‐dependent. Furthermore, GS‐B transport in both models was inhibited by chlorodinitrobenzene (CDNB), with an inhibitory constant of 46.8±0.9 μM in freshly isolated PTC. In Caco‐2 cells, the inhibitory potency of CDNB was approximately 20 fold higher. Finally, efflux of GS‐B from freshly isolated PTC from Mrp2‐deficient (TR−) rats was studied. As compared to normal rat PTC, transport characteristics were not different. We conclude that in freshly isolated rat PTC glutathione conjugate excretion is mediated by other organic anion transporters rather than by Mrp2. British Journal of Pharmacology (2001) 134, 931–938; doi:10.1038/sj.bjp.0704284