Abstract
The effect of spironolactone (SL) administration on 17α-ethynylestradiol (EE)-induced cholestasis was studied, with emphasis on expression and activity of Mrps. Adult male Wistar rats were divided into the following groups: EE (5 mg/kg daily for 5 days, s.c.), SL (200 μmol/kg daily for 3 days, i.p.), EE+SL (same doses, SL administered the last 3 days of EE treatment), and controls. SL prevented the decrease in bile salt-independent fraction of bile flow induced by EE, in association with normalization of biliary excretion of glutathione. Western blot studies indicate that EE decreased the expression of multidrug resistance-associated protein 2 (Mrp2) by 41% and increased that of Mrp3 by 200%, whereas SL only affected Mrp2 expression (+60%) with respect to controls. The EE+SL group showed increased levels of Mrp2 and Mrp3 to the same extent as that registered for the individual treatments. Real-time polymerase chain reaction studies indicated that up-regulation of Mrp2 and Mrp3 by SL and EE, respectively, was at the transcriptional level. To estimate Mrp2 and Mrp3 activities, apical and basolateral excretion of acetaminophen glucuronide (APAP-glu), a common substrate for both transporters, was measured in the recirculating isolated perfused liver model. Biliary/perfusate excretion ratio was decreased in EE (-88%) and increased in SL (+36%) with respect to controls. Coadministration of rats with SL partially prevented (-53%) impairment induced by EE in this ratio. In conclusion, SL administration to EE-induced cholestatic rats counteracted the decrease in bile flow and biliary excretion of glutathione and APAP-glu, a model Mrp substrate, findings associated with up-regulation of Mrp2 expression.
Footnotes
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This work was supported by grants from Agencia Nacional de Promoción Científica y Tecnológica, Consejo Nacional de Investigaciones Científicas y Técnicas and Universidad Nacional de Rosario.
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doi:10.1124/dmd.107.016519.
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ABBREVIATIONS: Bsep, bile salt export pump; BSDF, bile salt-dependent component of bile flow; BSIF, bile salt-independent flow; AE2, anion exchanger 2; APAP, acetaminophen; APAP-glu, acetaminophen glucuronide; EE, ethynylestradiol; GSH, glutathione; MPM, mixed plasma membrane; IPL, isolated perfused liver; Mrp2, multidrug resistance-associated protein 2; Mrp3, multidrug resistance-associated protein 3; SL, spironolactone; UGT, UDP-glucuronosyltransferase; PCR, polymerase chain reaction; PXR, pregnane X receptor.
- Received May 8, 2007.
- Accepted August 6, 2007.
- The American Society for Pharmacology and Experimental Therapeutics
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