Abstract
We previously showed that the function of renal multidrug resistance protein (Mrp) 2 (Abcc2) is reduced by endothelin (ET)-1 signaling through an ETB receptor, nitric-oxide synthase (NOS), cGMP, and protein kinase C and that this pathway was activated by several nephrotoxicants (Masereeuw et al., 2000; Terlouw et al., 2001; Notenboom et al., 2002, 2004). Here, we determined the long-term effects on Mrp2-mediated transport (luminal fluorescein methotrexate accumulation) of short-term (30 min) exposure to ET-1 and the aminoglycoside antibiotic, gentamicin. Our data show that over the 3 h following exposure, proximal tubules recovered fully from the initial decrease in Mrp2-mediated transport and that transport activity was not changed 9 h later. However, 24 h after exposure, luminal accumulation of an Mrp2 substrate had increased by 50%. Increased transport at 24 h was accompanied by an increased transporter protein content of the luminal plasma membrane as measured by immunostaining. Blocking ET-1 signaling at the ETB receptor or downstream at NOS or guanylyl cyclase abolished both stimulation of transport and increased transporter expression. Thus, regardless of whether signaling was initiated by a short exposure to ET-1 or to a nephrotoxicant, the time course of Mrp2 response to ETB signaling was the same and was multiphasic. Finally, when tubules were exposed to gentamicin for 30 min and removed to gentamicin-free medium for 24 h, they were less sensitive to acute gentamicin toxicity than paired controls not initially exposed to the drug. Thus, short-term exposure to ET-1 or gentamicin resulted in long-term protection against a second insult.
Footnotes
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This study was supported by the Dutch Kidney Foundation and by the Mount Desert Island Biological Laboratory Center for Membrane Toxicity Studies. Data were presented at the American Society of Nephrology (ASN) Renal Week 2003 (Nov 12-17; San Diego, CA) SU-PO137 and ASN Renal Week 2004 (Oct 27-Nov 1; St. Louis, MO) F-PO130.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.105.089094.
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ABBREVIATIONS: Mrp, multidrug resistance protein; MTX, methotrexate; FL, fluorescein; ET, endothelin; NOS, nitric-oxide synthase; PKC, protein kinase C; l-NMMA, NG-methyl-l-arginine acetate salt; RES701-1, cyclo(-Gly-Asn-Trp-His-Gly-Thr-Ala-Pro-Asp)-Trp-Phe-Phe-Asn-Tyr-Tyr-Trp-OH; ODQ, oxadiazole quinoxalin; PXR, pregnane X nuclear receptor.
- Received May 4, 2005.
- Accepted August 4, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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