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Goutam K, Ielasi FS, Pardon E, Steyaert J, Reyes N. Structural basis of sodium-dependent bile salt uptake into the liver. Nature 2022; 606:1015-1020. [PMID: 35545671 PMCID: PMC9242856 DOI: 10.1038/s41586-022-04723-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Accepted: 04/04/2022] [Indexed: 02/08/2023]
Abstract
The liver takes up bile salts from blood to generate bile, enabling absorption of lipophilic nutrients and excretion of metabolites and drugs1. Human Na+–taurocholate co-transporting polypeptide (NTCP) is the main bile salt uptake system in liver. NTCP is also the cellular entry receptor of human hepatitis B and D viruses2,3 (HBV/HDV), and has emerged as an important target for antiviral drugs4. However, the molecular mechanisms underlying NTCP transport and viral receptor functions remain incompletely understood. Here we present cryo-electron microscopy structures of human NTCP in complexes with nanobodies, revealing key conformations of its transport cycle. NTCP undergoes a conformational transition opening a wide transmembrane pore that serves as the transport pathway for bile salts, and exposes key determinant residues for HBV/HDV binding to the outside of the cell. A nanobody that stabilizes pore closure and inward-facing states impairs recognition of the HBV/HDV receptor-binding domain preS1, demonstrating binding selectivity of the viruses for open-to-outside over inward-facing conformations of the NTCP transport cycle. These results provide molecular insights into NTCP ‘gated-pore’ transport and HBV/HDV receptor recognition mechanisms, and are expected to help with development of liver disease therapies targeting NTCP. Structural studies of human Na+–taurocholate co-transporting polypeptide in complex with nanobodies reveal mechanisms for bile salts transport and HBV recognition involving an open-pore intermediate state.
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Affiliation(s)
- Kapil Goutam
- Membrane Protein Mechanisms Group, European Institute of Chemistry and Biology, University of Bordeaux, CNRS-UMR5234, Pessac, France.,Membrane Protein Mechanisms Unit, Institut Pasteur, Paris, France
| | | | - Els Pardon
- Structural Biology Brussels, Vrije Universiteit Brussel, VUB, Brussels, Belgium.,VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Jan Steyaert
- Structural Biology Brussels, Vrije Universiteit Brussel, VUB, Brussels, Belgium.,VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Nicolas Reyes
- Membrane Protein Mechanisms Group, European Institute of Chemistry and Biology, University of Bordeaux, CNRS-UMR5234, Pessac, France. .,Membrane Protein Mechanisms Unit, Institut Pasteur, Paris, France.
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2
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Dabur R. Identification of molecular pathways affected by treatment with heartwood water extract of Pterocarpus marsupium in MCF 7 cancer cell line. J Herb Med 2017. [DOI: 10.1016/j.hermed.2017.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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3
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Masuda M, Ichikawa Y, Shimono K, Shimizu M, Tanaka Y, Nara T, Miyauchi S. Electrophysiological characterization of human Na+/taurocholate cotransporting polypeptide (hNTCP) heterologously expressed in Xenopus laevis oocytes. Arch Biochem Biophys 2014; 562:115-21. [DOI: 10.1016/j.abb.2014.08.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 08/12/2014] [Accepted: 08/14/2014] [Indexed: 12/27/2022]
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4
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Döring B, Lütteke T, Geyer J, Petzinger E. The SLC10 carrier family: transport functions and molecular structure. CURRENT TOPICS IN MEMBRANES 2013. [PMID: 23177985 DOI: 10.1016/b978-0-12-394316-3.00004-1] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The SLC10 family represents seven genes containing 1-12 exons that encode proteins in humans with sequence lengths of 348-477 amino acids. Although termed solute carriers (SLCs), only three out of seven (i.e. SLC10A1, SLC10A2, and SLC10A6) show sodium-dependent uptake of organic substrates across the cell membrane. These include the uptake of bile salts, sulfated steroids, sulfated thyroidal hormones, and certain statin drugs by SLC10A1 (Na(+)-taurocholate cotransporting polypeptide (NTCP)), the uptake of bile salts by SLC10A2 (apical sodium-dependent bile acid transporter (ASBT)), and uptake of sulfated steroids and sulfated taurolithocholate by SLC10A6 (sodium-dependent organic anion transporter (SOAT)). The other members of the family are orphan carriers not all localized in the cell membrane. The name "bile acid transporter family" arose because the first two SLC10 members (NTCP and ASBT) are carriers for bile salts that establish their enterohepatic circulation. In recent years, information has been obtained on their 2D and 3D membrane topology, structure-transport relationships, and on the ligand and sodium-binding sites. For SLC10A2, the putative 3D morphology was deduced from the crystal structure of a bacterial SLC10A2 analog, ASBT(NM). This information was used in this chapter to calculate the putative 3D structure of NTCP. This review provides first an introduction to recent knowledge about bile acid synthesis and newly found bile acid hormonal functions, and then describes step-by-step each individual member of the family in terms of expression, localization, substrate pattern, as well as protein topology with emphasis on the three functional SLC10 carrier members.
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Affiliation(s)
- Barbara Döring
- SLC10 family research group, Institute of Pharmacology and Toxicology, Justus Liebig University Giessen, Biomedical Research Center (BFS), Giessen, Germany
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Stieger B. The role of the sodium-taurocholate cotransporting polypeptide (NTCP) and of the bile salt export pump (BSEP) in physiology and pathophysiology of bile formation. Handb Exp Pharmacol 2011:205-59. [PMID: 21103971 DOI: 10.1007/978-3-642-14541-4_5] [Citation(s) in RCA: 200] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Bile formation is an important function of the liver. Bile salts are a major constituent of bile and are secreted by hepatocytes into bile and delivered into the small intestine, where they assist in fat digestion. In the small intestine, bile salts are almost quantitatively reclaimed and transported back via the portal circulation to the liver. In the liver, hepatocytes take up bile salts and secrete them again into bile for ongoing enterohepatic circulation. Uptake of bile salts into hepatocytes occurs largely in a sodium-dependent manner by the sodium taurocholate cotransporting polypeptide NTCP. The transport properties of NTCP have been extensively characterized. It is an electrogenic member of the solute carrier family of transporters (SLC10A1) and transports predominantly bile salts and sulfated compounds, but is also able to mediate transport of additional substrates, such as thyroid hormones, drugs and toxins. It is highly regulated under physiologic and pathophysiologic conditions. Regulation of NTCP copes with changes of bile salt load to hepatocytes and prevents entry of cytotoxic bile salts during liver disease. Canalicular export of bile salts is mediated by the ATP-binding cassette transporter bile salt export pump BSEP (ABCB11). BSEP constitutes the rate limiting step of hepatocellular bile salt transport and drives enterohepatic circulation of bile salts. It is extensively regulated to keep intracellular bile salt levels low under normal and pathophysiologic situations. Mutations in the BSEP gene lead to severe progressive familial intrahepatic cholestasis. The substrates of BSEP are practically restricted to bile salts and their metabolites. It is, however, subject to inhibition by endogenous metabolites or by drugs. A sustained inhibition will lead to acquired cholestasis, which can end in liver injury.
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Affiliation(s)
- Bruno Stieger
- Division of Clinical Pharmacology and Toxicology, University Hospital, 8091, Zurich, Switzerland.
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6
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Mita S, Suzuki H, Akita H, Hayashi H, Onuki R, Hofmann AF, Sugiyama Y. Vectorial transport of unconjugated and conjugated bile salts by monolayers of LLC-PK1 cells doubly transfected with human NTCP and BSEP or with rat Ntcp and Bsep. Am J Physiol Gastrointest Liver Physiol 2006; 290:G550-6. [PMID: 16474011 DOI: 10.1152/ajpgi.00364.2005] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Na(+)-taurocholate-cotransporting peptide (NTCP)/SLC10A1 and bile salt export pump (BSEP)/ABCB11 synergistically play an important role in the transport of bile salts by the hepatocyte. In this study, we transfected human NTCP and BSEP or rat Ntcp and Bsep into LLC-PK1 cells, a cell line devoid of bile salts transporters. Transport by these cells was characterized with a focus on substrate specificity between rats and humans. The basal to apical flux of taurocholate across NTCP- and BSEP-expressing LLC-PK1 monolayers was 10 times higher than that in the opposite direction, whereas the flux across the monolayer of control and NTCP or BSEP single-expressing cells did not show any vectorial transport. The basal to apical flux of taurocholate was saturated with a K(m) value of 20 microM. Vectorial transcellular transport was also observed for cholate, chenodeoxycholate, ursodeoxycholate, their taurine and glycine conjugates, and taurodeoxycholate and glycodeoxycholate, whereas no transport of lithocholate was detected. To evaluate the respective functions of NTCP and BSEP and to compare them with those of rat Ntcp and Bsep, we calculated the clearance by each transporter in this system. A good correlation in the clearance of the examined bile salts (cholate, chenodeoxycholate, ursodeoxycholate, and their taurine or glycine conjugates) was observed between transport by human and that of rat transporters in terms of their rank order: for NTCP, taurine conjugates > glycine conjugates > unconjugated bile salts, and for BSEP, unconjugated bile salts and glycine conjugates > taurine conjugates. In conclusion, the substrate specificity of human and rat NTCP and BSEP appear to be very similar at least for monovalent bile salts under physiological conditions.
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Affiliation(s)
- Sachiko Mita
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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Bonkobara M, Thongsong B, Ohmori T, Matsuki N, Inaba M, Ono K. Effects of epidermal growth factor on placental amino acids uptake in pregnant rats. J Vet Med Sci 2002; 64:689-92. [PMID: 12237513 DOI: 10.1292/jvms.64.689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To evaluate the effects of epidermal growth factor (EGF) on placental amino acids uptake, transport activities for L-proline, L-leucine, and L-alanine were kinetically examined in placental microvillous vesicles(PMV) obtained from pregnant rats administered with EGF(100 and 200 microg/kg/day) from day 18 to 21 of pregnancy. The Vmax of Na(+)-dependent proline uptake remarkably increased with a dose-dependent manner of EGF, while Km did not change. In contrast, Vmax and Km values of Na(+)-dependent and -independent alanine, and Na(+)-independent leucine uptake were not affected. These results suggested that EGF enhanced proline transport activity in placental microvillous membranes, resulting in an increase of proline concentration in the fetal blood. The selective up-regulation of proline uptake was considered to contribute to fetal growth by EGF.
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Affiliation(s)
- Makoto Bonkobara
- Department of Veterinary Clinical Pathobiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan
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Cramer S, Beveridge M, Kilberg M, Novak D. Physiological importance of system A-mediated amino acid transport to rat fetal development. Am J Physiol Cell Physiol 2002; 282:C153-60. [PMID: 11742808 DOI: 10.1152/ajpcell.2002.282.1.c153] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fetal growth and development are dependent on the delivery of amino acids from maternal amino acid pools to the fetal blood. This is accomplished via transfer across the apical and basal plasma membrane of the placental syncytiotrophoblast. The aim of this study was to determine whether inhibition of system A (amino acid transporter) was associated with a decrease in fetal weight in the rat. System A is a ubiquitous Na(+)-dependent amino acid transporter that actively transports small zwitterionic amino acids. In brief, system A was inhibited by infusing a nonmetabolizable synthetic amino acid analog, 2-(methylamino)isobutyric acid from days 7-20 of gestation. On day 20, the rats were killed and tissues (maternal liver, fetuses, and placentas) were collected for analysis. The degree of system A inhibition was determined, as was the impact of said inhibition on fetal and maternal weights, system A-mediated placental transport, and placental system A-mediated transporter expression. Our results suggest that when system A is inhibited, fetal weight is diminished [control group: -3.55 +/- 0.04 g (n = 113), experimental group: -3.29 +/- 0.04 g (n = 128)], implying an integral role for system A transport in fetal growth and development in the rat.
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Affiliation(s)
- Stuart Cramer
- Department of Pediatrics, University of Florida College of Medicine, Gainesville, Florida 32610, USA
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Shoda J, Kano M, Oda K, Kamiya J, Nimura Y, Suzuki H, Sugiyama Y, Miyazaki H, Todoroki T, Stengelin S, Kramer W, Matsuzaki Y, Tanaka N. The expression levels of plasma membrane transporters in the cholestatic liver of patients undergoing biliary drainage and their association with the impairment of biliary secretory function. Am J Gastroenterol 2001; 96:3368-78. [PMID: 11774951 DOI: 10.1111/j.1572-0241.2001.05339.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVES Percutaneous transhepatic biliary drainage (PTBD) has been believed to reduce hyperbilirubinemia in patients with obstructive cholestasis and to lessen liver injury through bile acid retention. The efficacy may be closely related to the capability of cholestatic liver to produce and secrete bile, which in turn depends on the expressions and functional activities of plasma membrane transporters in the liver. The aim of the present study was to determine the expression levels of these transporters in the cholestatic liver of patients undergoing PTBD. METHODS A total of 24 patients who had experienced obstructive cholestasis and had undergone preoperative PTBD were included in the study. Liver biopsy specimens were analyzed to determine the expression levels of the multidrug resistance-associated proteins (MRP) MRP2 and MRP3 and the canalicular bile salt export pump BSEP in the liver. RESULTS The messenger RNA (mRNA) levels of MRP2, the canalicular bilirubin conjugate export pump, and bile salt export pump (BSEP) were unchanged in liver specimens from the 14 patients well drained by PTBD but were reduced in specimens from the 10 patients poorly drained, compared to the levels of control subjects. Immunostainings of MRP2 and BSEP outlined the canalicular membrane domain but seemed fuzzy to varying degrees in specimens obtained from cholestatic liver, especially in specimens from liver that had been poorly drained, in contrast to the linear and intense localization in the liver of control subjects, correlating with the impaired bilirubin conjugate and bile acid secretion. The mRNA of MRP3, functioning as an inducible export pump for bilirubin conjugate and bile acid, was expressed not only in the cholestatic liver but also in the liver of control subjects, and the mRNA level was increased in specimens from both the cholestatic liver that had been well drained and from the liver that had been poorly drained. Immunostaining of MRP3 was observed in the epithelia of intrahepatic bile ducts in the liver of both control subjects and cholestatic patients, and in the epithelia of proliferated bile ductules and the hepatocytes surrounding the portal tracts in the cholestatic liver. CONCLUSIONS From the results of the present study, it is concluded that 1) the mRNA and immunohistochemical expression levels of MRP2 and BSEP may be altered in the cholestatic liver of patients undergoing PTBD; 2) both the decreased mRNA levels and the diminished canalicular membrane localization may be associated with the impairment of bile formation and secretion, i.e., the efficacy of PTBD; and 3) upregulated MRP3 in the cholangiocytes and hepatocytes may play a significant role in bile acid transport in the cholestatic hepatobiliary system.
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Affiliation(s)
- J Shoda
- Department of Gastroenterology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan
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10
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Shiao T, Iwahashi M, Fortune J, Quattrochi L, Bowman S, Wick M, Qadri I, Simon FR. Structural and functional characterization of liver cell-specific activity of the human sodium/taurocholate cotransporter. Genomics 2000; 69:203-13. [PMID: 11031103 DOI: 10.1006/geno.2000.6329] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Bile salts are rapidly removed from the circulation by the liver-specific sodium/taurocholate cotransporter (SLC10A1). To understand factors controlling its liver-specific expression, we isolated human SLC10A1 from a YAC chromosomal clone. SLC10A1 spans approximately 23 kb distributed over five exons. The major transcription start site is at 299 bp, and a minor start site is at 395 bp from the translational start site. A 1.2-kb portion of the 5' flanking region was sequenced and shown to contain a number of liver-enriched elements, but no TATA box. Using secreted alkaline phosphatase reporter constructs liver-specific expression was examined. Transient transfection demonstrated that SLC10A1 promoter expression was selectively expressed eightfold in FAO and rat hepatocytes, while deletion mutants demonstrated liver-specific expression in a region extending from -5 to +198 bp, which contained putative sites for C/EBP and HNF3. Mutations of the C/EBP site resulted in loss of 77% of transcriptional activity. Cotransfection of C/EBP, but not other putative liver-enriched binding factors, increased SLC10A1 promoter activity. Electrophoretic mobility shift assays demonstrated specific protein-DNA interactions that involved C/EBPalpha and beta. These studies demonstrate that the TATA-less human SLC10A1 promoter exhibits liver-specific activity and its regulatory elements contain binding sites for C/EBP, which contributes specifically to its transcriptional regulation.
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Affiliation(s)
- T Shiao
- Department of Medicine, University of Colorado Health Sciences Center and Denver Veterans Affairs Medical Center, 4200 East Ninth Avenue, Denver, Colorado 80262, USA
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Abstract
Benign recurrent intrahepatic cholestasis is a rare autosomal recessive disorder characterized by repeated episodes of intense pruritus and jaundice. Each attack lasts from several weeks to months before resolving spontaneously. Patients are completely asymptomatic for months to years between symptomatic periods. The disorder does not lead to progressive liver disease. Although attacks seem to be associated with a viral prodrome, an inciting viral agent or toxin has not been defined. Genetic studies have mapped the defect of this disorder to the long arm of chromosome 18 and a gene that codes for a P-type ATPase, which appears to be involved in aminophospholipid transport. Therapy during symptomatic periods is supportive and aimed at relief of severe pruritus until the episode resolves spontaneously.
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Affiliation(s)
- V A Luketic
- Department of Medicine, Hepatology Section, Medical College of Virginia Commonwealth University, Richmond, Virginia, USA
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THONGSONG B, MUKAI K, BONKOBARA M, UCHIDE T, OGAWA H, MIYAZAWA K, TAGUCHI K, YAMADA H, SATOH K, ONO K. Proline Uptake into Equine Placental Microvillous Membrane Vesicles. J Equine Sci 1999. [DOI: 10.1294/jes.10.21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Affiliation(s)
- Boonrit THONGSONG
- Faculty of Veterinary Science, Chulalongkorn University, Bangkok THAILAND, and Laboratory of Veterinary Clinical Pathobiology Department of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
- Laboratory of Veterinary Clinical Pathobiology Department of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Kazutaka MUKAI
- Laboratory of Veterinary Clinical Pathobiology Department of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Makoto BONKOBARA
- Laboratory of Veterinary Clinical Pathobiology Department of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Tsuyoshi UCHIDE
- Laboratory of Veterinary Clinical Pathobiology Department of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Hiroyuki OGAWA
- Laboratory of Veterinary Emergency Medicine, Department of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Kiyoshi MIYAZAWA
- Department of Veterinary Reproduction Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro 080-8555, Japan
| | - Kiyoshi TAGUCHI
- Department of Veterinary Surgery, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro 080-8555, Japan
| | - Haruo YAMADA
- Department of Veterinary Surgery, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro 080-8555, Japan
| | - Kunitada SATOH
- Department of Veterinary Reproduction Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro 080-8555, Japan
| | - Kenichiro ONO
- Laboratory of Veterinary Clinical Pathobiology Department of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
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Bonkobara M, Thongsong B, Matsuki N, Inaba M, Ono K. Proline, leucine, and alanine transport in placental microvillous membrane vesicles prepared from late gestational rats. J Vet Med Sci 1998; 60:1081-5. [PMID: 9819760 DOI: 10.1292/jvms.60.1081] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To characterize the active transport of amino acids across the placenta, uptakes of proline, leucine, and alanine were kinetically examined in placental microvillous membrane vesicles (PMV) prepared from rats in the late gestational period. Uptake rates of these amino acids in PMV showed saturable hyperbolic curves that obeyed Michaelis-Menten kinetics. Proline, leucine, and alanine transport were demonstrated to be carrier mediated systems with sodium-dependent, -independent, and both manner, respectively. In addition, sodium-dependent L-alanine transport showed two different systems, and new sodium-independent alanine transport system (K(m) of 1.12 mM) was observed in rat placenta. From these results, rat placenta has carrier mediated amino acid transport systems, and possesses at least three different transport systems for alanine.
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Affiliation(s)
- M Bonkobara
- Department of Veterinary Medical Science, Graduate School of Agricultural and Life Sciences, University of Tokyo, Japan
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Olinga P, Merema M, Sandker GW, Slooff MJ, Meijer DK, Groothuis GM. Uptake of taurocholic acid in human hepatocytes isolated from livers of donors of different age. J Pediatr Gastroenterol Nutr 1998; 27:366-8. [PMID: 9740216 DOI: 10.1097/00005176-199809000-00021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Affiliation(s)
- P Olinga
- Groningen Institute for Drug Studies, Department of Pharmacokinetics and Drug Delivery, University Centre for Pharmacy, The Netherlands
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15
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Konieczko EM, Ralston AK, Crawford AR, Karpen SJ, Crawford JM. Enhanced Na+-dependent bile salt uptake by WIF-B cells, a rat hepatoma hybrid cell line, following growth in the presence of a physiological bile salt. Hepatology 1998; 27:191-9. [PMID: 9425937 DOI: 10.1002/hep.510270130] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Although bile salts are toxic to the liver at high plasma concentrations, the effects of physiological concentrations of bile salts on normal hepatic function are poorly understood. We examined the effect of taurocholate (TC) on the basolateral uptake of [3H]TC in WIF-B cells, a hybrid cell line stably exhibiting in vitro the structural and functional polarity of hepatocytes. Cells were grown in the absence or presence of TC (50 micromol/L) over 12 days, and then incubated with [3H]TC concentrations ranging from 1 to 250 micromol/L. For both control and TC-grown cells, uptake of [3H]TC was linear over 2 minutes. In control cells, the Km for [3H]TC Na+-dependent uptake over 1 minute was 6 +/- 5 micromol/L, and the Vmax was 45 +/- 6 pmol TC/mg protein/min (+/- SEM). TC-grown cells exhibited no significant change in Km but showed a doubling of Vmax to 87 +/- 6 pmol TC/mg protein/min (P < .005). In both control and TC-grown cells, maximal uptake of [3H]TC occurred following 10 to 12 days in culture, with TC-grown cells consistently showing greater rates of [3H]TC uptake from 4 to 14 days in culture. Western blots immunostained for the basolateral Na+-dependent plasma membrane protein, ntcp, revealed the appropriate approximately 50-kd band in control and TC-grown cells, and confocal immunofluorescence microscopy demonstrated staining along the basolateral plasma membrane. Northern blots hybridized with a cDNA probe directed against ntcp indicated a modest TC-induced increase in mRNA levels. Reverse-transcriptase polymerase chain reaction (RT-PCR) using RNA isolated from WIF-B cells and oligonucleotide primers specific for rat ntcp or human NTCP transcripts revealed only the presence of the rat ntcp transcript. We conclude that bile salts, at concentrations normally found in mammalian portal blood, may be capable of promoting enhanced hepatocellular bile salt uptake via an increase in basolateral Na+-dependent plasma membrane transport capacity.
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Affiliation(s)
- E M Konieczko
- Department of Pathology, Yale University School of Medicine, New Haven, CT 06520-8023, USA
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Abstract
Glutamine plays an important role in fetal nutrition. This study explored the transport of [3H]glutamine into apical and basal predominant membrane vesicles derived from rat and human placenta. Na+-dependent glutamine transport was present in both apical and basal predominant vesicles derived from 20- and, to a lesser degree, 14-day gestation rat placenta. Amino-acid transport systems A, ASC-like, B(o,+) (in apical membrane vesicles) and, perhaps, y+L were involved in Na+-dependent glutamine transport. Na+-dependent glutamine uptake into human placental microvillus and basolateral membrane vesicles also occurred via several distinct transport activities. Glutamine transport via system N was not detected in either rat or human placental preparations. Na+-dependent glutamine transport in the rat was more pronounced in basal as compared to apical membrane vesicles. Conversely, in the human preparations, activity was significantly higher in microvillus as compared to basolateral membrane vesicles. It is concluded that Na+-dependent glutamine transport occurs through a variety of transport agencies in both the rat and human placenta. Transport varies with ontogeny and between species.
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Affiliation(s)
- D A Novak
- Department of Pediatrics, University of Florida College of Medicine, Gainesville, USA
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17
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Stieger B, Zhang J, O'Neill B, Sjövall J, Meier PJ. Differential interaction of bile acids from patients with inborn errors of bile acid synthesis with hepatocellular bile acid transporters. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 244:39-44. [PMID: 9063443 DOI: 10.1111/j.1432-1033.1997.00039.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
People with genetic or acquired defects in the biosynthesis of bile acids may suffer from cholestasis. Patients with a deficiency of 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase from 3 beta, 7 alpha-dihydroxy- and 3 beta, 7 alpha, 12 alpha-trihydroxy-5-cholenoic acids, the sulfated and partially glycine-conjugated forms of which are found in their urine and bile. 3-Oxo-delta 4 bile acids are detected in the urine of patients with a deficiency of 5 beta-reductase. It has been postulated that these unusual bile acids might act as cholestatic agents in these patients. The aim of the present study was to test this hypothesis in an in vitro system, since the abnormal bile acids would be metabolized in in vivo experiments. Basolateral (sinusoidal) and canalicular plasma membrane vesicles were isolated from rat liver. A rapid filtration method was used to determine transport of cholyltaurine in the presence of model bile acids into the isolated vesicles. It was found that 3 beta, 7 alpha-dihydroxy-5-cholenoic acid and 7 alpha-hydroxy-3-oxo-4-cholenoic acid both inhibited the apical, ATP-dependent transport system for cholyltaurine in a competitive manner with K(m) values of 15 microM and 16 microM, respectively. Radioactively labeled 3 beta, 7 alpha-dihydroxy-5-cholenoyltaurine and 7 alpha-hydroxy-3-oxo-4-cholenoyltaurine were not transported by the same transport system. The same types of experiments were performed with basolateral plasma membrane vesicles. It was found that, in contrast to the canalicular ATP-dependent bile acid transport system, only 7 alpha-hydroxy-3-oxo-4-cholenoyltaurine was a competitive inhibitor of the sodium-dependent transport system for cholyltaurine with a K(m) of 16 microM. Studies with radioactively labeled 7 alpha-hydroxy-3-oxo-4-cholenoyltaurine and 3 beta, 7 alpha-dihydroxy-5-cholenoyltaurine revealed that 7 alpha-hydroxy-3-oxo-4-cholenoyltaurine was transported in a sodium-dependent manner into basolateral rat liver plasma membrane vesicles, whereas 3 beta, 7 alpha-dihydroxy-5-cholenoyltaurine was not transported in a sodium-dependent way. These results support the hypothesis that the unusual bile acids found in patients with defects in bile acid biosynthesis might act as cholestatic agents by inhibiting the canalicular ATP-dependent transport system for bile acids which constitutes the rate-limiting step in the overall process of bile acid transport across hepatocytes. Furthermore, the experiments demonstrated that, despite similar substrate specificities, the basolateral sodium-dependent and the apical ATP-dependent transport system for cholyltaurine might have different recognition sites for bile acids.
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Affiliation(s)
- B Stieger
- University Hospital, Department of Medicine, Zürich, Switzerland
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18
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Malandro MS, Beveridge MJ, Kilberg MS, Novak DA. Effect of low-protein diet-induced intrauterine growth retardation on rat placental amino acid transport. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 271:C295-303. [PMID: 8760058 DOI: 10.1152/ajpcell.1996.271.1.c295] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Given the central role of the placenta in nutrient transport to the fetus, one might propose that maternal nutrition would have a regulatory effect on this nutrient delivery. We have examined the effect of a low-protein adequate-calorie diet on specific amino acid transport processes by the rat placenta. Maternal weight, fetal weight, and placental weight were all significantly reduced in dams fed a low-protein (5% casein), isocaloric diet when compared with dams pair-fed a control (20% casein) diet. Even though maternal serum amino acid levels were maintained in the low-protein animals, fetomaternal serum amino acid ratios were significantly reduced, suggesting a reduction in nutrient transfer to the fetus. Apical and basal membrane vesicles were isolated from the placental trophoblast and were used to examine the amino acid transport capacity of both maternal-facing and fetal-facing membranes, respectively. Na+-dependent neutral amino acid transport mediated by system A was decreased in both membrane preparations, while transport mediated by system ASC was unaffected. The Na+-dependent anionic amino acid uptake by system X(-)AG (EAAC1) was reduced on the basal membrane, while the Na+-independent component was similar between the low-protein and control diet-fed dams. Cationic amino acid uptake was also reduced on both membrane surfaces. A decreased steady-state mRNA content for EAAC1 and CAT1 (system y+) suggests that reduced synthesis of the transporter proteins is responsible for the decrease in transport activity. Taken together, these data support the hypothesis that maternal protein malnutrition affects nutrient delivery to the fetus by downregulation of specific amino acid transport proteins.
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Affiliation(s)
- M S Malandro
- Department of Biochemistry, University of Florida College of Medicine, Gainesville 32610, USA
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19
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Oude Elferink RP, Meijer DK, Kuipers F, Jansen PL, Groen AK, Groothuis GM. Hepatobiliary secretion of organic compounds; molecular mechanisms of membrane transport. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1241:215-68. [PMID: 7640297 DOI: 10.1016/0304-4157(95)00006-d] [Citation(s) in RCA: 249] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- R P Oude Elferink
- Department of Gastrointestinal and Liver Diseases, Academic Medical Center, AZ Amsterdam, The Netherlands
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20
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Novak DA, Beveridge MJ, Salhab AS, Tebbett IR, Shiverick KT. Effect of chronic cocaine administration on amino acid uptake in rat placental membrane vesicles. Life Sci 1995; 56:1779-87. [PMID: 7739352 DOI: 10.1016/0024-3205(95)00149-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This study evaluated the effects of chronic exposure to cocaine during pregnancy on amino acid uptake in placental membrane vesicles. Pregnant rats received 62 mg/kg of cocaine hydrochloride by intraperitoneal (IP) injection as a divided daily dose on gestation days 8-19 inclusive. Fetal body weights were significantly decreased by 19% in the cocaine group, while placental weights were unchanged. Placental apical membrane vesicles were prepared from control and cocaine-treated animals, and marker enzyme enrichments for alkaline phosphatase and [3H]-dihydroalprenolol binding did not differ between cocaine and control groups. Rates of uptake (10 sec) of selected radiolabeled amino acids were measured utilizing a rapid filtration technique. Na(+)-dependent apical membrane [3H]-glutamine transport (50 microM) was reduced by 95% (p < 0.05) in cocaine-treated compared to control placentas. Uptake of 50 microM [3H]-methyl aminoisobutyric acid (MeAIB) into apical membranes was also decreased by 43% (p < 0.05) in cocaine membranes. Na(+)-independent [3H]-arginine transport (10 microM), however, did not differ between control or cocaine-treated groups. In summary, chronic cocaine administration selectively inhibited the transport of glutamine and MeAIB into apical membrane vesicles, but had minimal effect on arginine transport. We postulate that this diminution in uptake may contribute to the fetal growth retardation noted in our model.
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Affiliation(s)
- D A Novak
- Department of Pediatrics, University of Florida, Gainesville 32610, USA
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21
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Malandro MS, Beveridge MJ, Kilberg MS, Novak DA. Ontogeny of cationic amino acid transport systems in rat placenta. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 267:C804-11. [PMID: 7943209 DOI: 10.1152/ajpcell.1994.267.3.c804] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Gestational regulation of the placental transfer of amino acids from maternal to fetal circulations is essential for the proper development of the fetus. The cationic amino acid transport systems of the microvillous (maternal facing) and basal (fetal facing) membranes of the rat placental syncytiotrophoblast were examined. Inhibition analysis documented the presence of three kinetically distinct cationic amino acid transport mechanisms: a single Na(+)-dependent mechanism in the microvillous membrane, which increased in activity from 14 to 20 days gestation but was absent from the basal membrane throughout the entire gestational period (system Bo,+), and two Na(+)-independent transport systems in both membrane domains, one that is completely inhibited by leucine, which increased in activity in both the microvillous and basal membrane domains, and the other that is leucine insensitive, which remained fairly constant in the basal membrane and increased throughout gestation in the microvillous membrane (system y1+). Northern analysis with the system y1+ cDNA revealed a specific band of approximately 7.4-7.9 kb, which increased with increasing gestational age.
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Affiliation(s)
- M S Malandro
- Department of Biochemistry, University of Florida College of Medicine, Gainesville 32610-0296
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22
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Sandker GW, Weert B, Olinga P, Wolters H, Slooff MJ, Meijer DK, Groothuis GM. Characterization of transport in isolated human hepatocytes. A study with the bile acid taurocholic acid, the uncharged ouabain and the organic cations vecuronium and rocuronium. Biochem Pharmacol 1994; 47:2193-200. [PMID: 7913319 DOI: 10.1016/0006-2952(94)90255-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The uptake and efflux of three categories of substrates were measured in isolated human hepatocytes and compared to those in rat hepatocytes. In addition, the extent to which the in vitro experiments quantitatively reflect liver function in vivo in both species was investigated. The anionic bile acid taurocholic acid was taken up by isolated human hepatocytes at a considerably lower rate than observed in isolated rat hepatocytes. Taurocholic acid uptake both in human hepatocytes and in liver plasma membrane vesicles showed sodium dependency. The uptake rate of taurocholic acid in isolated hepatocytes of both species was quantitatively compatible with the reported liver clearance of the bile acid in vivo. Ouabain uptake rate in isolated human hepatocytes was lower than in rat hepatocytes. This species difference was in accordance with pharmacokinetic studies in vivo on hepatic clearance of ouabain in man and rat. Uptake of vecuronium into human hepatocytes was about a factor of 10 lower than that in rat hepatocytes. Uptake into and efflux from human hepatocytes was comparable for the two short acting muscle relaxants vecuronium and rocuronium. Since distribution to the liver is considered to be a major factor in termination of action of vecuronium and rocuronium these observations were in line with the human pharmacokinetic profiles. In conclusion, the uptake rate of the studied model compounds in human hepatocytes appeared to be lower than that in rat hepatocytes. These observed transport rates reflected the relative hepatic transport rates observed in these species in the intact organism, but the absolute values in both species for some substrates may have been somewhat lower than calculated from in vivo data. It is concluded that transport studies in isolated hepatocytes are suitable for comparative drug transport studies, but are less precise in the prediction of quantitative membrane transport.
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Affiliation(s)
- G W Sandker
- Department of Pharmacology, University of Groningen, The Netherlands
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23
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Isolation of sinusoidal and canalicular liver plasma membranes: Effects of frozen storage of human material. Toxicol In Vitro 1994; 8:173-80. [DOI: 10.1016/0887-2333(94)90180-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/1993] [Revised: 07/23/1993] [Indexed: 11/21/2022]
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24
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Hagenbuch B, Meier PJ. Molecular cloning, chromosomal localization, and functional characterization of a human liver Na+/bile acid cotransporter. J Clin Invest 1994; 93:1326-31. [PMID: 8132774 PMCID: PMC294097 DOI: 10.1172/jci117091] [Citation(s) in RCA: 325] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
We have used a cDNA probe from a cloned rat liver Na+/taurocholate cotransporting polypeptide (Ntcp) to screen a human liver cDNA library. A 1,599-bp cDNA clone that encodes a human Na+/taurocholate cotransporting polypeptide (NTCP) was isolated. The human NTCP consists of 349 amino acids (calculated molecular mass of 38 kD) and exhibits 77% amino acid homology with the rat Ntcp. In vitro translation experiments indicate that the protein is glycosylated and has a molecular weight similar to the rat Ntcp. Injection of in vitro transcribed cRNA into Xenopus laevis oocytes resulted in the expression of Na(+)-dependent taurocholate uptake. Saturation kinetics indicated that the human NTCP has a higher affinity for taurocholate (apparent Km = 6 microM) than the previously cloned rat protein (apparent Km = 25 microM). NTCP-mediated taurocholate uptake into oocytes was inhibited by all major bile acid derivatives (100 microM), bumetanide (500 microM), and bromosulphophthalein (100 microM). Southern blot analysis of genomic DNA from a panel of human/hamster somatic cell hybrids mapped the human NTCP gene to chromosome 14.
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Affiliation(s)
- B Hagenbuch
- Department of Medicine, University Hospital, Zürich, Switzerland
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25
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Petzinger E. Transport of organic anions in the liver. An update on bile acid, fatty acid, monocarboxylate, anionic amino acid, cholephilic organic anion, and anionic drug transport. Rev Physiol Biochem Pharmacol 1994; 123:47-211. [PMID: 8209137 DOI: 10.1007/bfb0030903] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- E Petzinger
- Institute of Pharmacology and Toxicology, University Giessen, Germany
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26
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Affiliation(s)
- W Hardikar
- Department of Pediatric Gastroenterology/Hepatology, Yale University, New Haven, Connecticut 05610
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27
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Boyer JL, Hagenbuch B, Ananthanarayanan M, Suchy F, Stieger B, Meier PJ. Phylogenic and ontogenic expression of hepatocellular bile acid transport. Proc Natl Acad Sci U S A 1993; 90:435-8. [PMID: 8421672 PMCID: PMC45677 DOI: 10.1073/pnas.90.2.435] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The phylogenic and ontogenic expression of mRNA for the Na+/bile acid cotransporter was determined by Northern analysis utilizing a full-length cDNA probe recently cloned from rat liver. mRNA was detected in several mammalian species, including rat, mouse, and man, but could not be found in livers from nonmammalian species, including chicken, turtle, frog, and small skate. When expression of the bile acid transporter in developing rat liver was studied, mRNA was detected between 18 and 21 days of gestation, at the time when Na(+)-dependent bile acid transport is first detected. Two hepatoma cell lines (HTC and HepG2), the latter of which is known to have lost the Na+/bile acid cotransport system, also did not express mRNA for this transporter. Finally, when mRNA from the lower vertebrate (the small skate) was injected into Xenopus oocytes, only a sodium-independent, chloride-dependent transport system for bile acids was expressed, confirming the integrity of the mRNA and consistent with prior functional studies of bile acid transport in this species. These findings establish that the Na+/bile acid cotransport mRNA is first transcribed in mammalian species, a process that is recapitulated late during mammalian fetal development in rat liver, and that this mRNA is lost in dedifferentiated hepatocytes. In contrast, the mRNA for a multispecific Na+/independent organic anion transport system is transcribed earlier in vertebrate evolution.
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Affiliation(s)
- J L Boyer
- Mt. Desert Island Biological Laboratory, Salsbury Cove, ME 04672
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28
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Wolters H, Kuipers F, Slooff MJ, Vonk RJ. Adenosine triphosphate-dependent taurocholate transport in human liver plasma membranes. J Clin Invest 1992; 90:2321-6. [PMID: 1469089 PMCID: PMC443385 DOI: 10.1172/jci116120] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Transport systems involved in uptake and biliary secretion of bile salts have been extensively studied in rat liver; however, little is known about these systems in the human liver. In this study, we investigated taurocholate (TC) transport in canalicular and basolateral plasma membrane vesicles isolated from 15 human livers (donor age 6-64 yr). ATP stimulated the uptake of TC into both canalicular and basolateral human liver plasma membrane vesicles (cLPM and blLPM, respectively). Considerable interindividual variations in the transport velocity were observed in the different membrane preparations used: 9.0 +/- 1.3 (mean +/- SEM, n = 17; range 1.6-18.0) and 9.3 +/- 2.0 (range 1.1-29.8) pmol TC.mg protein-1.min-1 at 1.0 microM TC for cLPM and blLPM, respectively. TC transport was temperature sensitive and showed saturation kinetics with a high affinity for TC (Km 4.2 +/- 0.7 microM and 3.7 +/- 0.5 microM for cLPM and blLPM, respectively). Transport was dependent on the ATP concentration and saturable (Km 0.25 +/- 0.03 mM, n = 3). Neither nitrate, which reduces membrane potential, nor the protonophore FCCP strongly inhibited ATP-dependent TC transport, indicating that membrane potential and proton gradient are not involved in this process. TC transport was significantly inhibited by the classical anion transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonate (250 microM) and the glutathione conjugate S-(2,4-dinitrophenyl)glutathione (100 microM). In conclusion, high affinity ATP-dependent TC transport is present in human liver at both the canalicular and the basolateral sides of the hepatocyte.
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Affiliation(s)
- H Wolters
- Department of Pediatrics, University of Groningen, The Netherlands
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29
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Novak D, Ray W, Carver J, Grossman S. Developmental changes in hepatic basolateral membrane lipid composition and fluidity. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1111:59-64. [PMID: 1390865 DOI: 10.1016/0005-2736(92)90274-p] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Membrane fluidity and lipid composition influence the activity of a variety of membrane proteins. Decreased rates of hepatic ion clearance are associated with the neonatal period. We postulated that hepatic basolateral membranes derived from suckling animals might be less fluid than those from adult animals. Basolateral membrane vesicles were prepared from the livers of 1-week-old (SBLMV) and adult (ABLMV) rats by a Percoll gradient method. Na+/K(+)-ATPase activities were similar in the two groups. Double bond index, cholesterol and cholesterol/phosphorus ratios were significantly higher in SBLMV compared with ABLMV, while lipid phosphorus and relative percentages of phospholipid subclasses did not differ. Fluorescence anisotropy measured using diphenylhexatriene as well as 2-(9-anthroyloxy)stearate was significantly greater in SBLMV compared with ABLMV, while measurements made with 12-(9-anthroyloxy)stearate were similar in both age groups. Mean excited state lifetimes, lifetime distributions, and rotational correlation times were similar in both groups. These data suggest that hepatic basolateral membranes derived from suckling rats are less fluid than those from adult animals and further suggest that this difference may be due to increased cholesterol in hepatic basolateral membranes derived from suckling animals.
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Affiliation(s)
- D Novak
- Department of Pediatrics, University of South Florida College of Medicine, Tampa
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30
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Said HM, Hoefs J, Mohammadkhani R, Horne DW. Biotin transport in human liver basolateral membrane vesicles: a carrier-mediated, Na+ gradient-dependent process. Gastroenterology 1992; 102:2120-5. [PMID: 1587433 DOI: 10.1016/0016-5085(92)90341-u] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The characteristics of biotin transport into human liver were examined using purified liver basolateral membrane vesicle (BLMV) preparations. Biotin uptake by BLMVs was mostly due to transport of the vitamin into the inside of vesicles. In the presence of an Na+ gradient (out greater than in), biotin transport with time was significantly higher than that in the presence of a K+ gradient and showed transient accumulation (overshoot). High concentrations of unlabeled biotin and related compounds caused significant cis inhibition in biotin transport in the presence of an Na+ (but not a K+) gradient. Transport of biotin as a function of concentration in the presence of an Na+ gradient included a saturable component, while it was lower and linear in the presence of a K+ gradient. Apparent Km and Vmax of the saturable Na+ gradient-dependent component were 1.22 mumol/L and 4.76 pmol.mg protein-1 x 10 s-1, respectively. Induction of a negative or positive intravascular potential using valinomycin-K diffusion methodology did not affect biotin transport into BLMVs. Also, neither the anion-exchange inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid nor 4-acetamido-4-isothiocyanostilbene-2,2'-disulfonic acid caused significant inhibition in biotin transport. These results indicate that biotin transport into human liver occurs via a specialized, carrier-mediated transport system. This system is Na(+)-gradient dependent and transports the vitamin via an electroneutral process.
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Affiliation(s)
- H M Said
- Veterans Administration Medical Center, Long Beach, California
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31
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Burwen SJ, Schmucker DL, Jones AL. Subcellular and molecular mechanisms of bile secretion. INTERNATIONAL REVIEW OF CYTOLOGY 1992; 135:269-313. [PMID: 1618608 DOI: 10.1016/s0074-7696(08)62043-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
One of the liver's principal functions is the formation of bile, which is requisite for digestion of fat and elimination of detoxified drugs and metabolites. Bile is a complex fluid made up of water, electrolytes, bile acids, pigments, proteins, lipids, and a multitude of chemical breakdown products. In this review, we have summarized the source of various biliary components, the route by which they end up in bile, including the underlying subcellular and molecular mechanisms, and their contribution to bile formation. One of the reasons why bile formation is so complex is that there are many mechanisms with overlapping substrate specificities, i.e., many biochemically unrelated biliary constituents share common transport mechanisms. Additionally, biliary constituents may reach bile by more than one pathway. Some biliary components are critical for bile formation; others are of minor significance for bile formation but play a major physiological role. The major driving force for bile formation is the uptake and transcellular transport of bile salts by hepatocytes. The energy for bile formation comes from the sodium gradient created by the basolateral Na+/K(+)-ATPase, to which bile salt transport is coupled. The secretory pathway for bile salts involves uptake at the basolateral surface of the hepatocyte, vectorial transcellular movement, and transport across the canalicular membrane into the canalicular lumen. Hydrophilic bile salts are taken up via a sodium-dependent, saturable, carrier-mediated process coupled to the Na+/K(+)-ATPase. This uptake mechanism is also shared by other substrates, such as electroneutral lipids, cyclic oligopeptides, and a wide variety of drugs. Hydrophobic bile acids are taken up by a sodium-independent facilitated carrier-mediated mechanism in common with other organic ions, including sulfated bile acids, sulfobromophthalein, bilirubin, glutathione, and glucuronides, or by nonsaturable passive diffusion. Two major carrier proteins have been identified on the hepatocyte basolateral membrane: a 48-kDa protein that appears to be involved with Na(+)-dependent bile salt uptake, and a 54-kDa protein, thought to be associated with Na(+)-independent bile salt uptake. The intracellular transport of bile salts may involve cytosolic carrier proteins, of which several have been identified. Some evidence suggests a vesicular transport mechanism for bile salts. Since bile acids clearly do not enter the cell by endocytosis, formation of transport vesicles must be a more distal event in the transcellular translocation process. Some bile salts appear to be transported within the same unilamellar vesicles that are involved in the secretion of cholesterol and phospholipid.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- S J Burwen
- Cell Biology and Aging Section, Veterans Administration Medical Center, San Francisco, California 94121
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32
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Wolters H, Spiering M, Gerding A, Slooff MJ, Kuipers F, Hardonk MJ, Vonk RJ. Isolation and characterization of canalicular and basolateral plasma membrane fractions from human liver. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1069:61-9. [PMID: 1932051 DOI: 10.1016/0005-2736(91)90104-g] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A method is described for the isolation of subfractions from human liver plasma membranes, enriched in canalicular domains (cLPM) and basolateral domains (blLPM), respectively, and the results are compared to those obtained with rat liver. The studies were performed in 18 human livers. The cLPM (isolated at densities 1.103-1.127 for human and 1.036-1.127 for rat cLPM) from human as well as rat liver showed a lower density than the blLPM (1.141-1.161 for human and 1.151-1.172 for rat blLPM). Human and rat blLPM were characterized by increased levels of (Na+/K+)-ATPase (relative enrichment 33 and 21, respectively). Both human and rat cLPM showed high specific activities of leucine aminopeptidase; relative enrichment factors were 42 and 31, respectively. Mg(2+)-ATPase and alkaline phosphatase, specific canalicular enzymes in rat liver, were only slightly enriched in the cLPM of human liver, which indicates that these enzymes are not suitable as marker enzymes for human liver cLPM. Both cLPM and blLPM of human and rat origin were only slightly contaminated with mitochondria, lysosomes, Golgi membranes and endoplasmic reticulum. Total recoveries of cLPM and blLPM were 0.02 mg protein/g liver each for the human membrane preparations, compared to 0.07 and 0.16 mg protein/g liver for the membranes prepared from rat liver. Analysis of membrane fluidity revealed that the human liver cLPM were more rigid than blLPM (mean difference in fluorescence polarization PDPH 0.024). They contained more cholesterol (0.43 vs. 0.30 mumol/mg protein) and phospholipids (0.54 vs. 0.39 mumol/mg protein, respectively), which was compatible to rat liver plasma membrane fractions. This study shows that besides similarities, there are several differences between human and rat liver plasma membrane fractions.
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Affiliation(s)
- H Wolters
- Department of Pediatrics, University of Groningen, The Netherlands
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33
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Affiliation(s)
- M H Nathanson
- Department of Medicine, Yale University School of Medicine, New Haven, Connecticut 06510
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34
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Renner EL, Reichen J. The role of bile salt uptake in canalicular bile formation. Transport systems and acinar heterogeneity. J Hepatol 1991; 13:140-3. [PMID: 1744416 DOI: 10.1016/0168-8278(91)90806-m] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- E L Renner
- Department of Clinical Pharmacology, University of Berne, Switzerland
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35
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Min AD, Johansen KL, Campbell CG, Wolkoff AW. Role of chloride and intracellular pH on the activity of the rat hepatocyte organic anion transporter. J Clin Invest 1991; 87:1496-502. [PMID: 2022722 PMCID: PMC295228 DOI: 10.1172/jci115159] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Previous studies in cultured rat hepatocytes revealed that initial uptake of sulfobromophthalein (BSP) was markedly reduced upon removal of Cl- from the medium. In the present study, unidirectional Cl- gradients were established in short-term cultured rat hepatocytes and their effect on BSP uptake was determined. These investigations revealed that BSP uptake requires external Cl- and is not stimulated by unidirectional Cl- gradients, suggesting that BSP transport is not coupled to Cl- transport. In contrast, BSP transport is stimulated by an inside-to-outside OH- gradient, consistent with OH- exchange or H+ cotransport. As the presence of Cl- is essential for but not directly coupled to BSP transport, binding of 35S-BSP to hepatocytes was determined at 4 degrees C. This revealed an approximately 10-fold higher affinity of cells for BSP in the presence as compared to the absence of Cl- (Ka = 3.2 +/- 0.8 vs. 0.42 +/- 0.09 microM-1; P less than 0.02). Affinity of BSP for albumin was Cl(-)-independent, and was approximately 10% of its affinity for cells in the presence of Cl-. These results indicate that extracellular Cl- modulates the affinity of BSP for its hepatocyte transporter.
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Affiliation(s)
- A D Min
- Liver Research Center, Albert Einstein College of Medicine, Bronx, New York 10461
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Kurisu H, Kamisaka K, Koyo T, Yamasuge S, Igarashi H, Maezawa H, Uesugi T, Tagaya O. Organic anion transport study in mutant rats with autosomal recessive conjugated hyperbilirubinemia. Life Sci 1991; 49:1003-11. [PMID: 1890927 DOI: 10.1016/0024-3205(91)90301-q] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The EHBR is a mutant rat strain with congenital conjugated hyperbilirubinemia bred from a Sprague-Dawley rat. Transport of conjugated bilirubin, indocyanine green, and tetrabromosulfophtalein from liver to bile is severely impaired in these rats. Serum bilirubin amounts to 6.0 +/- 0.05 mg/dl (n = 4) in adult rats, with 97% conjugates. The bile flow is reduced to about 65% of the control group, whereas total bile acid in 10-min bile samples is similar. Liver histology of 10 week-old rats revealed neither intracellular pigmentation nor architectural abnormalities.
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Affiliation(s)
- H Kurisu
- Third Department of Internal Medicine, Tokyo Medical and Dental University, Japan
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Mailliard M, Kilberg M. Sodium-dependent neutral amino acid transport by human liver plasma membrane vesicles. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(18)77303-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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