Basic Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Aug 7, 2015; 21(29): 8817-8825
Published online Aug 7, 2015. doi: 10.3748/wjg.v21.i29.8817
Expression of renal Oat5 and NaDC1 transporters in rats with acute biliary obstruction
Anabel Brandoni, Adriana Mónica Torres
Anabel Brandoni, Adriana Mónica Torres, Pharmacology, Department of Physiological Sciences, Faculty of Biochemical and Pharmaceutical Sciences, National University of Rosario, CONICET, Rosario 2000, Argentine
Author contributions: Brandoni A has designed research, performed research, contributed new reagents, analyzed data, wrote the paper; Torres AM has designed research, performed research, contributed new reagents, analyzed data, wrote the paper.
Supported by Grants from Fondo para la Investigación Científica y Tecnológica (FONCyT), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Rosario (UNR).
Institutional review board statement: The study was reviewed and approved by the National University of Rosario Institutional Review Board (Resol. C.S., No. 823/2013).
Institutional animal care and use committee statement: All procedures involving animals were reviewed and approved by the Institutional Animal Care and Use Committee of the Faculty of Biochemical and Pharmaceutical Sciences-UNR (Resol., No, 637/2012).
Conflict-of-interest statement: Both authors have no conflict of interest.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Adriana Mónica Torres, PhD, Professor of Pharmacology, Pharmacology, Department of Physiological Sciences, Faculty of Biochemical and Pharmaceutical Sciences, National University of Rosario, CONICET, Suipacha 531, Rosario 2000, Argentina. admotorres@yahoo.com.ar
Telephone: +54-341-4393400
Received: January 21, 2015
Peer-review started: January 29, 2015
First decision: June 2, 2015
Revised: June 18, 2015
Accepted: July 3, 2015
Article in press: July 3, 2015
Published online: August 7, 2015
Processing time: 198 Days and 18.1 Hours
Abstract

AIM: To examine renal expression of organic anion transporter 5 (Oat5) and sodium-dicarboxylate cotransporter 1 (NaDC1), and excretion of citrate in rats with acute extrahepatic cholestasis.

METHODS: Obstructive jaundice was induced in rats by double ligation and division of the common bile duct (BDL group). Controls underwent sham operation that consisted of exposure, but not ligation, of the common bile duct (Sham group). Studies were performed 21 h after surgery. During this period, animals were maintained in metabolic cages in order to collect urine. The urinary volume was determined by gravimetry. The day of the experiment, blood samples were withdrawn and used to measure total and direct bilirubin as indicative parameters of hepatic function. Serum and urine samples were used for biochemical determinations. Immunoblotting for Oat5 and NaDC1 were performed in renal homogenates and brush border membranes from Sham and BDL rats. Immunohistochemistry studies were performed in kidneys from both experimental groups. Total RNA was extracted from rat renal tissue in order to perform reverse transcription polymerase chain reaction. Another set of experimental animals were used to evaluate medullar renal blood flow (mRBF) using fluorescent microspheres.

RESULTS: Total and direct bilirubin levels were significantly higher in BDL animals, attesting to the adequacy of biliary obstruction. An important increase in mRBF was determined in BDL group (Sham: 0.53 ± 0.12 mL/min per 100 g body weight vs BDL: 1.58 ± 0.24 mL/min per 100 g body weight, P < 0.05). An increase in the urinary volume was observed in BDL animals. An important decrease in urinary levels of citrate was seen in BDL group. Besides, a decrease in urinary citrate excretion (Sham: 0.53 ± 0.11 g/g creatinine vs BDL: 0.07 ± 0.02 g/g creatinine, P < 0.05) and an increase in urinary excretion of H+ (Sham: 0.082 ± 0.03 μmol/g creatinine vs BDL: 0.21 ± 0.04 μmol/g creatinine, P < 0.05) were observed in BDL animals. We found upregulations of both proteins Oat5 and NaDC1 in brush border membranes where they are functional. Immunohistochemistry technique corroborated these results for both proteins. No modifications were observed in Oat5 mRNA and in NaDC1 mRNA levels in kidney from BDL group as compared with Sham ones.

CONCLUSION: Citrate excretion is decreased in BDL rats, at least in part, because of the higher NaDC1 expression. Using the outward gradient of citrate generated by NaDC1, Oat5 can reabsorb/eliminate different organic anions of pathophysiological importance.

Keywords: Cholestasis; Kidney; Transporters; Organic anions

Core tip: Organic anion transporter 5 (Oat5) is an organic anion/dicarboxylate exchanger which has impact on renal excretion of hormones, drugs and xenobiotics. The primary function of sodium-dicarboxylate cotransporter 1 (NaDC1) is to reabsorb filtered Krebs cycle intermediates, such as citrate. We found upregulations of both transporters and a decrease in urinary citrate excretion in bile duct-ligated rats. Citrate excretion is decreased at least in part, because of the higher NaDC1 expression. Using the outward gradient of citrate generated by NaDC1, Oat5 can reabsorb/eliminate different organic anions of pathophysiological importance. Attention might be paid for those drugs transported by this protein because their pharmacokinetics may be altered during cholestasis.