Functional reconstitution of the canalicular bile salt transport system of rat liver.

Ruetz, Stephan; Hugentobler, Gabriel; Meier, Peter J.

doi:10.1073/pnas.85.16.6147

Cited by 64 publications

(42 citation statements)

References 33 publications

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“…In the liver, the transport from the portal blood into bile requires distinct systems for uptake [2] and export across the apical membrane [3]. Also, different systems for transport across the basolateral and apical membrane [4] of intestinal cells operate.…”

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confidence: 99%

Hepatic uptake and intestinal absorption of bile acids in the rabbit

Aldini

Roda

Montagnani

et al. 1994

Eur J Clin Investigation

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Abstract. The existence of transoorters for bile acidsIntroduction (BA) in liver and intestine has been well documented, but information is still needed as to their respective transport capacity. In the present investigation, we compared the hepatic and intestinal transport rates for BA, using perfused livers and intestines. The livers and intestines were separately perfused and doseresponse curves (0.25-10 mM) for tauroursodeoxycholate, taurocholate and taurodeoxycholate were obtained. The intestinal and mesenteric concentration and bile acid pattern were also evaluated in six non-fasting rabbits. Taurocholic, tauroursodeoxycholic and taurodeoxycholic acid ileal absorption showed saturation kinetics in the intestine as in the liver; the maximal uptake velocity for each bile acid in the liver was tenfold higher than the respective maximal transport velocity in the intestine; the Km values obtained in the liver were of the same order of magnitude, i.e. in the millimolar range. Taurocholic, tauroursodeoxycholic and taurodeoxycholic acid transport differences in the liver paralleled those in the intestine. Although the intestine was not homogeneously filled, the bile acid concentration in the ileal content fell into the range of the Km for the three studied bile acids, while the portal blood total bile acid concentration was inferior to the observed Kms of liver uptake. Therefore, both the hepatic and intestinal systems do not operate at their maximal transport rates at the prevailing concentrations in portal blood and luminal content, and the hepatic transport occurs at its highest efficiency (below the Km values) in physiological conditions. Both the liver and the intestine have been considered as main steps in the conservation of the enterohepatic circulation (EHC) of bile acids [l]. In the liver, the transport from the portal blood into bile requires distinct systems for uptake [2] and export across the apical membrane [3]. Also, different systems for transport across the basolateral and apical membrane [4] of intestinal cells operate. Therefore, the overall rate of bile acids (BA) extraction is the resultant of many processes. The kinetic parameters of the hepatic uptake of bile acids have been measured [5,6] and several systems have been identified and described in the liver [7-1 I], while an active absorption system for BA localized in the terminal ileum has been identified [12-191. It has been pointed out that besides active absorption in the ileum, passive diffusion in the jejunum helps maintain the EHC of BA [20]. Recent studies from our laboratory [21], moreover, have stressed the relative contribution of the active and passive route in the intestinal absorption of BA. These studies demonstrated that the passive component is limited mostly to dihydroxy unconjugated BA, while the transfer rates of conjugated bile acids from the lumen to the intestinal blood are largely dependent on active processes. Thus, in normal physiological conditions, where little amounts of unconjugated BA are present in the intes...

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confidence: 99%

Hepatic uptake and intestinal absorption of bile acids in the rabbit

Aldini

Roda

Montagnani

et al. 1994

Eur J Clin Investigation

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“…In the experiments described in this paper, comparable results were obtained with both methods. Adapting exactly the reconstitution conditions described by Ruetz et al [24] to the intestinal peptide transport system from rabbit jejunum with a lipid/ protein ratio of 1 : 1 did not result in the formation of liposomes with a significant intravesicular volume. We therefore could not confirm the claims of Ruetz et al [24] that their method may be universally applicable to transport systems.…”

Section: Discussionmentioning

confidence: 99%

“…Functional reconstitution of the uptake system for p-lactam antibiotics and oligopeptides in proteoliposomes prepared from brush border membrane proteins For reconstitution of the transport system for 8-lactam antibiotics and oligopeptides, brush border membrane vesicles were solubilized with the nonionic detergents Triton X-100 or n-octyl glucoside in the presence of lipids and subsequently liposomes were prepared by a gel filtration method [24]. The proteinllipid ratio was varied between 1 : 1 and 1 :40.…”

Section: Resultsmentioning

confidence: 99%

“…For reconstitution of membrane proteins and transport systems a variety of different methods has been described [27 -291. For the functional reconstitution of the intestinal peptide transport system we have chosen the method of liposome formation by gel filtration, successfully used for the functional reconstitution of a variety of transporters and receptors [30-361 including the rat liver canalicular bile salt transport system [24].…”

Section: Discussionmentioning

confidence: 99%

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Intestinal absorption of β‐lactam antibiotics and oligopeptides

Kramer

Girbig

Gutjahr

et al. 1992

European Journal of Biochemistry

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The H+‐dependent uptake system responsible for the enteral absorption of oligopeptides and orally active β‐lactam antibiotics was functionally reconstituted into liposomes. Membrane proteins from rabbit small intestinal brush border membrane vesicles were solubilized with n‐octyl glucoside and incorporated into liposomes using a gel filtration method. At protein/lipid ratios of 1:10 and 1:40, the uptake of the orally active α‐amino‐cephalosporin, D‐cephalexin into proteoliposomes was stimulated by an inwardly directed H+ gradient and was protein‐dependent. In these proteoliposomes the binding protein for oligopeptides and β‐lactam antibiotics of Mr 127000 could be labeled by direct photoaffinity labeling with [3H]benzylpenicillin revealing an identical binding specificity as in the original brush border membrane vesicles. The uptake system for β‐lactam antibiotics and oligopeptides showed a remarkable stereospecificity; only D‐cephalexin was taken up by intact brush border membrane vesicles, whereas the L‐enantiomer was not taken up to a significant extent. This stereospecificity for uptake was also seen after reconstitution of solubilized brush border membrane proteins into liposomes demonstrating a functional reconstitution of the peptide transporter. Both enantiomers however, bound to the 127‐kDa binding protein as was shown by a decrease in the extent of photoaffinity labeling of the 127‐kDa protein in the presence of both enantiomers. After reconstitution of subfractions of brush border membrane proteins obtained by wheat germ lectin affinity chromatography into proteoliposomes, only liposomes containing the 127‐kDa binding protein showed a significant uptake of D‐cephalexin whereas the L‐enantiomer was not transported. The uptake rates for D‐cephalexin into proteoliposomes correlated with the content of 127‐kDa binding protein in these liposomes as was determined by specific photoaffinity labeling with [3H]benzylpenicillin. The purified 127‐kDa binding protein was also reconstituted into liposomes and its ability for specific binding of substrates as well as stereospecific uptake of cephalexin could be restored. These results indicate that the binding protein for oligopeptides and β‐lactam antibiotics of Mr 127000 mediates the stereospecific and H+‐dependent transport of orally active β‐lactam antibiotics across the enterocyte brush border membrane. We therefore suggest that this 127‐kDa binding protein is the intestinal peptide transport system (or a component thereof).

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“…Canalicular transport of bile salt organic anions in rat Canalicular bile salt transport was initially characterized as a membrane potential driven process [19][20][21]. The high bile salt gradient, however, could not be achieved solely by a single membrane potential driven transporter.…”

Section: Hepatobiliary Transport Of Bile Salt and Nonbile Salt Organimentioning

confidence: 99%

The canalicular multispecific organic anion transporter and conjugated hyperbilirubinemia in rat and man

Paulusma

Elferink

1997

Journal of Molecular Medicine

104

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The canalicular multispecific organic anion transporter and conjugated hyperbilirubinemia in rat and man Paulusma, C.C.; Oude Elferink, R.P.J. Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Download date: 22 Mar 2019& p . 1 : Abstract The human Dubin-Johnson syndrome is an autosomal recessive liver disease characterized by a chronic conjugated hyperbilirubinemia. Patients have impaired hepatobiliary transport of many endogenous and xenobiotic compounds. A similar disease phenotype has been described for a naturally occurring mutant Wistar rat strain, the TR -rat, which is defective in the, functionally defined, canalicular multispecific organic anion transporter (cMOAT). The complementary DNA encoding this protein has been cloned from rat and recently from human liver. cMOAT is a new member of the ATPbinding cassette transporter family, and homologous to the multidrug resistance-associated protein 1. A mutation in the cMOAT gene is responsible for the phenotype observed in TR -rats. This information should soon lead to a complete genetic characterization of the human DubinJohnson syndrome.

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Functional reconstitution of the canalicular bile salt transport system of rat liver.

Cited by 64 publications

References 33 publications

Hepatic uptake and intestinal absorption of bile acids in the rabbit

Hepatic uptake and intestinal absorption of bile acids in the rabbit

Intestinal absorption of β‐lactam antibiotics and oligopeptides

The canalicular multispecific organic anion transporter and conjugated hyperbilirubinemia in rat and man

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