Abstract
Multidrug resistance protein (MRP) 2 (MRP2; ABCC2), an organic anion transporter apically expressed in liver, kidney, and intestine, plays an important protective role through facilitating the efflux of potentially toxic compounds. We hypothesized that upon a toxic insult, MRP2 is up-regulated in mammalian kidney, thereby protecting the tissue from damage. We studied the effects of the nephrotoxicant gentamicin on the functional expression of MRP2 in transfected Madin-Darby canine kidney type II (MDCKII) cells and rat kidney. Transport of glutathionemethyl fluorescein by cells or calcein by isolated perfused rat kidney was measured to monitor MRP2 activity. MDCKII cells were exposed to gentamicin (0-1000 μM) for either 1 h, 24 h, or for 1 h followed by 24-h recovery. No effect was observed on MRP2 after 1-h exposure. After 24-h gentamicin exposure or after a 24-h recovery period following 1-h exposure, an increase in MRP2-mediated transport was seen. This up-regulation was accompanied by a 2-fold increase in MRP2 protein expression in the apical membrane, whereas the expression in total cell lysates remained unchanged. In perfused kidneys of rats exposed to gentamicin (100 mg/kg) for seven consecutive days, an increase in Mrp2 function and expression was found, which was prevented by addition of a dual endothelin-receptor antagonist, bosentan. We conclude that an increased shuttling of the transporter to the apical membrane takes place in response to gentamicin exposure, which is triggered by endothelin. Up-regulation of MRP2 in the kidney may be interpreted as part of a protective mechanism.
Footnotes
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This study was supported by the Dutch Kidney Foundation.
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doi:10.1124/jpet.106.104547.
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ABBREVIATIONS: MRP/Mrp, multidrug resistance protein; ABC, ATP-binding cassette; DMEM, Dulbecco's modified Eagle's medium; HBSS, Hanks' balanced salt solution; AM, acetoxymethylester; CMFDA, 5-chloromethylfluorescein diacetate; MK-571, (3-([{3-(2-[7-chloro-2-quinolinyl]ethenyl)phenyl}-{(3-dimethyl-amino-3-oxopropyl)-thio}-methyl]thio)propanoic acid); CDNB, 1-chloro-3,4-nitrobenzene; ET, endothelin; MD-CKII, Madin-Darby canine kidney type II; wt, wild type/wild-type; OK, opossum kidney; GS-MF, glutathione-methylfluorescein; LDH, lactate dehydrogenase; WH, Wistar-Hannover; PBS, phosphate-buffered saline; NFDM, nonfat dried milk; E-64, N-(trans-epoxysuccinyl)-l-leucine 4-guanidinobutylamide; PCR, polymerase chain reaction; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; Gent, gentamicin; WT, wild type.
- Received March 14, 2006.
- Accepted June 2, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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