ATP-dependent transport of unconjugated bilirubin by rat liver canalicular plasma membrane vesicles

L. Pascolo, E. J. Bayon, F. Cupelli, J. D. Ostrow, C. Tribelli

Research output: Contribution to journalArticle

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Abstract

The transport of highly purified 3H-labelled unconjugated bilirubin (UCB) was investigated in rat liver plasma membrane vesicles enriched in the canalicular domain and found to be stimulated (more than 5-fold) by the addition of ATP. Other nucleotides, such as AMP, ADP, GTP and a non-hydrolysable ATP analogue (adenosine 5'-[α,β-methylene] triphosphate), did not stimulate [3H]UCB transport, indicating that ATP hydrolysis was necessary for the stimulatory effect. [3H]UCB uptake occurred into an osmotically sensitive space. At an unbound bilirubin concentration ([Bf]) below saturation of the aqueous phase (no more than 70 nM UCB), the ATP-dependent transport followed saturation kinetics with respect to [Bf], with a K(m) of 26 ± 8 nM and a V(max) of 117 ± 11 pmol per 15 s per mg of protein. Unlabelled UCB inhibited the uptake of [3H]UCB, indicating that UCB was the transported species. Inhibitors of ATPase activity such as vanadate or diethyl pyrocarbonate decreased the ATP effect (59 ± 11% and 100% respectively). Daunomycin, a known substrate for multidrug resistance protein-1, and taurocholate did not inhibit the ATP-dependent [3H]UCB transport, suggesting that neither mdr-1 nor the canalicular bile acid transporter is involved in the canalicular transport of UCB. [3H]UCB uptake (both with and without ATP) in canalicular vesicles obtained from TR- rats was comparable to that in vesicles obtained from Wistar rats, indicating that the canalicular multispecific organic anion transporter, cMOAT, does not account for UCB transport. These results indicate that UCB is transported across the canalicular membrane of the liver cell by an ATP-dependent mechanism involving an as yet unidentified transporter.

Original languageEnglish
Pages (from-to)99-103
Number of pages5
JournalBiochemical Journal
Volume331
Issue number1
Publication statusPublished - Apr 1 1998

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Cell membranes
Bilirubin
Liver
Rats
Adenosine Triphosphate
Cell Membrane
Diethyl Pyrocarbonate
Taurocholic Acid
Daunorubicin
Vanadates
P-Glycoprotein
Adenosine Monophosphate
Guanosine Triphosphate
Adenosine
Adenosine Diphosphate
Adenosine Triphosphatases
Wistar Rats
Hydrolysis
Nucleotides

ASJC Scopus subject areas

  • Biochemistry

Cite this

Pascolo, L., Bayon, E. J., Cupelli, F., Ostrow, J. D., & Tribelli, C. (1998). ATP-dependent transport of unconjugated bilirubin by rat liver canalicular plasma membrane vesicles. Biochemical Journal, 331(1), 99-103.

ATP-dependent transport of unconjugated bilirubin by rat liver canalicular plasma membrane vesicles. / Pascolo, L.; Bayon, E. J.; Cupelli, F.; Ostrow, J. D.; Tribelli, C.

In: Biochemical Journal, Vol. 331, No. 1, 01.04.1998, p. 99-103.

Research output: Contribution to journalArticle

Pascolo, L, Bayon, EJ, Cupelli, F, Ostrow, JD & Tribelli, C 1998, 'ATP-dependent transport of unconjugated bilirubin by rat liver canalicular plasma membrane vesicles', Biochemical Journal, vol. 331, no. 1, pp. 99-103.
Pascolo, L. ; Bayon, E. J. ; Cupelli, F. ; Ostrow, J. D. ; Tribelli, C. / ATP-dependent transport of unconjugated bilirubin by rat liver canalicular plasma membrane vesicles. In: Biochemical Journal. 1998 ; Vol. 331, No. 1. pp. 99-103.
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