Identification and Functional Characterization of Bilitranslocase in Sea-Bass (Dicentrarchus labrax) Hepatopancreas

A. Delneri, R. Franca, M. Terdoslavich, S. Montanič, V. Čurin Šerbec, F. Tramer, M. Francese, S. Passamonti

Research output: Contribution to journalArticlepeer-review


The mammalian bilirubin transporter bilitranslocase (BTL, T.C.#2.A.65.1.1) is found in both absorptive (intestine) and excretory epithelia (liver, kidney) and in the vascular endothelium. The aim of this work was to investigate whether a BTL homologue is expressed also in fish hepatopancreas. Immunochemistry based on an antisequence antibody specific for rat liver BTL demonstrated the presence of such homologue in sea-bass (Dicentrarchus labrax) hepatopancreas. Furthermore the transport activity of such a carrier, measured as electrogenic bromosulphophthalein (BSP) uptake, was assayed in sea-bass microsomes, where it was inhibited by the same antibody. Transport activity in fish showed numerous kinetic similarities with rat, such as BSP K m(about 5 μM in both), bilirubin K i (about 0.1 μM), quercetin competitive K i (about 20 μM), and noncompetitive K i (about 85 μM). Biliverdin K i was instead nearly 10-fold higher in fish than in rat (0.97 ± 0.06 μM and 0.11 ± 0.01 μM, respectively). Fish BTL was found to exist in two different allosteric forms with different affinities for the substrate, similarly to rat liver BTL. It was found that sea-bass BTL is very sensitive to inhibition by HgCl 2, a major water pollutant, making it reasonable to exploit fish BTL activity as an ecotoxicological biosensor.

Original languageEnglish
Pages (from-to)2887-2900
Number of pages14
JournalAnalytical Letters
Issue number18
Publication statusPublished - Dec 2011


  • Bilitranslocase
  • Fish
  • Hepatopancreas
  • Hg inhibition

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Clinical Biochemistry
  • Biochemistry, medical
  • Electrochemistry
  • Spectroscopy


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