Uptake of the thioether S-(2,4-dinitrophenyl)glutathione (DNPSG) in canalicular plasma membrane vesicles from rat liver is enhanced in the presence of ATP and exhibits an overshoot with a transient 5.5-fold accumulation of DNPSG. Stimulation by ATP is not caused by the generation of a membrane potential, based on responses of the indicator dye oxonol V. ATP-dependent uptake has an apparent Km of 71 microM for DNPSG and a Vmax of 0.34 nmol.min-1.mg of vesicle protein-1. Protein thiol groups are essential for transport activity as indicated by the sensitivity of DNPSG transport to sulfhydryl reagents. There is competitive inhibition with other thioethers, S-hexylglutathione (Ki = 66 microM), the photoaffinity label S-(4-azidophenacyl)glutathione (Ki = 56 microM), as well as with glutathione disulfide (Ki = 0.44 mM) and with the bile acid taurocholate (Ki = 0.61 mM). GSH (2 mM) or cholate (0.4 mM) does not inhibit. Both glutathione disulfide and taurocholate show ATP-dependent transport in the canalicular membrane vesicles which is inhibited by DNPSG. No ATP-dependent transport is found for GSH. Transport of DNPSG is also inhibited competitively by alpha-naphthyl-beta-D-glucuronide (Ki = 0.42 mM) but not by alpha-naphthylsulfate (2 mM), and there is substantial inhibition with the glucuronides from ebselen and p-nitrophenol. The results indicate that the canalicular transport system for DNPSG is directly driven by ATP and that the biliary transport of other classes of compounds may also proceed via this system.
ATP-dependent S-(2,4-dinitrophenyl)glutathione transport in canalicular plasma membrane vesicles from rat liver.
T. Akerboom,V. Narayanaswami,Manuel Kunst,Helmut Sies
Published 1991 in Journal of Biological Chemistry
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- Publication year
1991
- Venue
Journal of Biological Chemistry
- Publication date
1991-07-15
- Fields of study
Biology, Medicine, Chemistry
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Semantic Scholar, PubMed
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