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Biliary
Impaired localisation and transport function of canalicular Bsep in taurolithocholate induced cholestasis in the rat
  1. F A Crocenzi1,
  2. A D Mottino1,
  3. E J Sánchez Pozzi1,
  4. J M Pellegrino1,
  5. E A Rodríguez Garay1,
  6. P Milkiewicz2,
  7. M Vore3,
  8. R Coleman4,
  9. M G Roma1
  1. 1Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas (CONICET-UNR), Rosario, Argentina
  2. 2Department of Gastroenterology, Pomeranian Medical School, Szczecin, Poland
  3. 3Graduate Center for Toxicology, University of Kentucky, Lexington, USA
  4. 4School of Biosciences, University of Birmingham, Birmingham, UK
  1. Correspondence to:
    Dr M G Roma, Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas, Suipacha 570, S2002LRL-Rosario, Argentina;
    ifise1{at}citynet.net.ar

Abstract

Background: Taurolithocholate induced cholestasis is a well established model of drug induced cholestasis with potential clinical relevance. This compound impairs bile salt secretion by an as yet unclear mechanism.

Aims: To evaluate which step/s of the hepatocellular bile salt transport are impaired by taurolithocholate, focusing on changes in localisation of the canalicular bile salt transporter, Bsep, as a potential pathomechanism.

Methods: The steps in bile salt hepatic transport were evaluated in rats in vivo by performing pharmacokinetic analysis of 14C taurocholate plasma disappearance. Bsep transport activity was determined by assessing secretion of 14C taurocholate and cholyl-lysylfluorescein in vivo and in isolated rat hepatocyte couplets (IRHC), respectively. Localisation of Bsep and F-actin were assessed both in vivo and in IRHC by specific fluorescent staining.

Results: In vivo pharmacokinetic studies revealed that taurolithocholate (3 μmol/100 g body weight) diminished by 58% canalicular excretion and increased by 96% plasma reflux of 14C taurocholate. Analysis of confocal images showed that taurolithocholate induced internalisation of Bsep into a cytosolic vesicular compartment, without affecting F-actin cytoskeletal organisation. These effects were reproduced in IRHC exposed to taurolithocholate (2.5 μM). Preadministration of dibutyryl-cAMP, which counteracts taurolithocholate induced impairment in bile salt secretory function in IRHC, restored Bsep localisation in this model. Furthermore, when preadministered in vivo, dibutyryl-cAMP accelerated recovery of both bile flow and bile salt output, and improved by 106% the cumulative output of 14C taurocholate.

Conclusions: Taurolithocholate impairs bile salt secretion at the canalicular level. Bsep internalisation may be a causal factor which can be prevented by dibutyryl-cAMP.

  • cholestasis
  • taurolithocholate
  • Bsep
  • actin cytoskeleton
  • dibutyryl-cAMP
  • TLC, taurolithocholate
  • BS, bile salts
  • BF, bile flow
  • CM, canalicular membrane
  • Bsep, bile salt export pump
  • ABC, ATP binding cassette
  • IRHC, isolated rat hepatocyte couplet
  • DB-cAMP, dibutyryl- cAMP
  • TC, taurocholate
  • CLF, cholyl-lysylfluorescein
  • PBS, phosphate buffered saline
  • cVA, canalicular vacuolar accumulation

https://doi.org/10.1136/gut.52.8.1170

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    Footnotes

    • This article is dedicated to the memory of Professor Roger Coleman, 13 August 1938–14 January 2003.

    • Presented in part at the Biennial Meeting of the International Association for the Study of the Liver (IASL), Madrid, Spain, April 2002, and published in abstract form ( J Hepatol2002;(Suppl 1): ).