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Beneficial Effect of Spironolactone Administration on Ethynylestradiol-Induced Cholestasis in the Rat: Involvement of Up-Regulation of Multidrug Resistance-Associated Protein 2

Instituto de Fisiología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina (M.L.R., S.S.M.V., M.G.L., A.D.M., V.A.C.); and Toyama Prefectural University, Toyama, Japan (S.I.)

The effect of spironolactone (SL) administration on 17-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.

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				A. Arias, S. S. M. Villanueva, M. L. Ruiz, M. G. Luquita, L. M. Veggi, J. M. Pellegrino, M. Vore, V. A. Catania, and A. D. Mottino Regulation of Expression and Activity of Rat Intestinal Multidrug Resistance-Associated Protein 2 by Cholestatic Estrogens Drug Metab. Dispos., June 1, 2009; 37(6): 1277 - 1285. [Abstract] [Full Text] [PDF]