Abstract
The present study examined how the multidrug resistance protein (MRP) 2, which is an ATP-dependent anionic conjugate transporter, also mediates transport of the chemotherapeutic cationic drug vinblastine (VBL). We show that ATP-dependent [3H]VBL (0.2 μM) uptake into membrane vesicles from Sf9 cells infected with a baculovirus encoding rabbit Mrp2 (Sf9-Mrp2) was similar to vesicles from mock-infected Sf9 cells (Sf9-mock) but could be stimulated by reduced glutathione (GSH) with a half-maximum stimulation of 1.9 ± 0.1 mM. At 5 mM GSH, initial ATP-dependent [3H]VBL uptake rates were saturable with an apparentKm of 1.5 ± 0.3 μM. The inhibitory effect of VBL on Mrp2-mediated ATP-dependent transport of the anionic conjugate [3H]leukotriene C4 was potentiated by increasing GSH concentrations. Membrane vesicles from Sf9-Mrp2 cells exhibited a ∼7-fold increase in initial GSH uptake rates compared with membrane vesicles from Sf9-mock cells. Uptake of [3H]GSH was osmotically sensitive, independent of ATP, and was trans-inhibited by GSH. The anionic conjugates estradiol-17β-d-glucuronide and leukotriene C4cis-inhibited [3H]GSH uptake but only in the presence of ATP. Whereas ATP-dependent [3H]VBL uptake was stimulated by GSH, VBL did not affect [3H]GSH uptake. Our results show that GSH is required for Mrp2-mediated ATP-dependent VBL transport and that Mrp2 transports GSH independent of VBL.
Footnotes
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Send reprint requests to: Dr. F. G. M. Russel, University of Nijmegen, Department of Pharmacology and Toxicology 233, P.O. Box 9101, 6500 HB Nijmegen, the Netherlands. E-mail:F.Russel{at}farm.kun.nl
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J.B.K. is supported by the Netherlands Organization for Scientific Research through Grant 805-05.041.
- Abbreviations:
- MRP
- multidrug resistance protein
- LTC4
- leukotriene C4
- VBL
- vinblastine
- VCR
- vincristine
- GSH
- reduced glutathione
- E217βG
- estradiol-17β-d-glucuronide
- DNP-SG
- S-dinitrophenyl-glutathione
- EHBR
- Eisai hyperbilirubinemic rat strain
- DTT
- dithiothreitol
- MK571
- 3-([{3-(2-[7-chloro-2-quinolinyl]ethenyl)phenyl}-{(3-dimethyl-amino-3-oxopropyl)-thio}-methyl]thio)propanoic acid
- YCF1
- yeast cadmium factor-1
- Received January 20, 1999.
- Accepted May 21, 1999.
- The American Society for Pharmacology and Experimental Therapeutics