![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
Vol. 299, Issue 1, 164-170, October 2001
Department of Pharmacy, Uppsala University (J.T., P.A.), Department of Molecular Medicine and Clinical Pharmacology, Uppsala University Hospital (H.M.), Uppsala, Sweden; Division of Gastroenterology and Hepatology (H.T., G.L., C.E.) and Clinical Pharmacology (F.S.), Huddinge University Hospital, Stockholm, Sweden; and Department of In Vitro Sciences, Pharmacia (P.G., B.S., B.L.), Stockholm, Sweden
 |
Abstract |
|---|
 Top
 Abstract
 Introduction
Materials and Methods
Results
Discussion
Conclusions
References
|
|---|
This investigation describes the expression and interindividual
variability in transcript levels of multiple drug efflux systems in the
human jejunum and compares the expression profiles in these cells with
that of the commonly used Caco-2 cell drug absorption model. Transcript
levels of ten-drug efflux proteins of the ATP-binding cassette
(ABC) transporter family [MDR1, MDR3, ABCB5, MRP1-6, and
breast cancer resistance protein (BCRP)], lung resistance-related protein (LRP), and CYP3A4 were determined using quantitative polymerase chain reaction in jejunal biopsies from 13 healthy human subjects and
in Caco-2 cells. All genes except ABCB5 were expressed,
and transcript levels varied between individuals only by a factor of 2 to 3. Surprisingly, BCRP and MRP2
transcripts were more abundant in jejunum than MDR1
transcripts. Jejunal transcript levels of the different ABC
transporters spanned a range of three log units with the rank order:
BCRP 
MRP2 > MDR1 MRP3 MRP6 MRP5 MRP1 > MRP4 > MDR3. Furthermore, transcript
levels of 9 of 10 ABC transporters correlated well between jejunum and
Caco-2 cells (r2 = 0.90). However,
BCRP exhibited a 100-fold lower transcript level in
Caco-2 cells compared with jejunum. Thus, the expression of a number of
efflux protein transcripts in jejunum are equal to, or even higher
than, that of MDR1, suggesting that the roles of these
proteins (in particular BCRP and MRP2) in intestinal drug efflux have
been underestimated. Also, we tentatively conclude that the Caco-2 cell
line is a useful model of jejunal drug efflux, if the low expression of
BCRP is taken into account.
| |
Introduction |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
Conclusions
References
|
|---|
Apart
from the multidrug resistance protein MDR1, many other more recently
discovered efflux proteins of the ATP-binding cassette (ABC)
transporter superfamily may influence the pharmacokinetics, tissue
distribution, and pharmacodynamics of drugs (Wacher et al., 1998
;
Ambudkar et al., 1999; Borst et al., 2000; Jonker et al., 2000). These
more recent discoveries include at least six different multidrug
resistance-associated proteins (MRPs) (Borst et al., 2000) as well as
breast cancer resistance protein (BCRP) (Doyle et al., 1998). Also, a
large number of ABC transporters are mainly known as expressed sequence
tags and have been assigned to different subfamilies according to their
similarity to known ABC transporters. One of these orphan ABC
transporters, ABCB5, was included in this study because of its
similarity to MDR1. The tissue expression pattern and the transcript
size of ABCB5 have led to it being described as a housekeeping
(expressed in all tissues) full-molecule (two transmembrane and two
ATP-binding domains) ABC transporter (Allikmets et al., 1996). Because
of the broad substrate specificities of these transporters, drugs of
many pharmacological classes interact with, or are substrates of, MDR1
(Ambudkar et al., 1999), BCRP (Doyle et al., 1998; Litman et al.,
2000), and the different MRPs (Borst et al., 2000). Furthermore, there
is a partial substrate overlap among MDR1, BCRP, and the MRPs. A
complex picture is emerging in which the pharmacokinetics and
pharmacodynamics of a drug can be influenced not only by more than one
efflux protein but also by functional polymorphism in those proteins
(Hoffmeyer et al., 2000). However, this complexity will only be
apparent if efflux proteins are expressed at significant levels in
human tissues. A number of publications have presented human expression
data for these efflux proteins, but only scattered information is
available regarding their expression in the human small intestine, a
rate-limiting barrier to oral drug absorption (e.g., Kool et al., 1997;
Doyle et al., 1998; Fromm et al., 2000; Maliepaard et al., 2001). A
systematic investigation of a wider selection of efflux proteins in the
human small intestine is therefore warranted.
Studies on the role of efflux mechanisms in the absorption of drugs are
generally performed in cell culture models such as the human intestinal
epithelial Caco-2 cell line (Braun et al., 2000). However, as is the
case for human tissues, only limited and mainly qualitative data on
efflux protein expression in this cell line are available (e.g.,
Gutmann et al., 1999; Hirohashi et al., 2000). A lack of awareness of
the expression of multiple efflux systems in the cell lines, as well as
in vivo, may potentially result in the erroneous classification of
drugs as being, for example, solely MDR1 substrates, since the drugs
could also be transported by other efflux proteins with overlapping
substrate specificity (e.g., BCRP). An investigation into the extent of expression of the various efflux proteins at the mRNA level in cell
culture models would be a first step in resolving this problem. In
addition, a quantitative comparison in this respect between the most
important absorption site for orally administered drugs, the human
jejunum, and the Caco-2 cell line will provide insight into the
usefulness of this cell line as a model for oral drug absorption.
We therefore investigated the mRNA expression levels of 10 efflux proteins of the ABC transporter superfamily in both the human jejunum and well differentiated Caco-2 cell monolayers grown on permeable support. In addition, we investigated the mRNA expression levels of lung resistance-related protein (LRP) and CYP3A4. Since jejunal biopsies from 13 healthy human subjects were used, it was also possible to perform a preliminary investigation into the interindividual variability of all mRNA levels.
| |
Materials and Methods |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
Conclusions
References
|
|---|
Tissue Samples and Cell Cultures. Human jejunal mucosa biopsies were obtained using a Watson capsule from 13 healthy volunteers (on no medication) ages 21 to 52 years (four female and nine male). Biopsies and all subsequent procedures were carried out with consent from the ethical review board of Huddinge University Hospital.
Caco-2 cells, a colorectal carcinoma cell line, were obtained from American Type Culture Collection (ATCC, Manassas, VA) and cultured at passage number 99 on Transwell polycarbonate filters (Costar, Cambridge, MA) for 21 days, as previously described (Artursson et al., 1996). For RNA isolation, filter-grown cells were harvested using
ice-cold phosphate-buffered saline and a cell scraper. Cells were kept
on ice during the scraping procedure and subsequently recovered by centrifugation.
Tissue and cell samples were frozen in liquid nitrogen and then stored
at 
80°C until required for RNA preparation.
RNA Extraction, Quantitation and Quality Check. Total RNA was isolated using the RNeasy mini kit (QIAGEN GmbH, Hilden, Germany) following the instructions provided by the manufacturer, with an additional on-column DNase treatment step (QIAGEN). Cells and tissues were homogenized using 3 sequential pulses (of homogenization) of 20 s each using a Heidolph DIAX 900 tissue homogenizer equipped with a 6G tool (Heidolph Instruments, Cinnaminson, NJ). RNA was quantified using the RiboGreen reagent from Molecular Probes (Eugene, OR), and RNA integrity was checked by assessing the sharpness of ribosomal RNA bands on a native 1% agarose gel using a 1× TBE running buffer (0.09 M Tris-borate, 0.002 M EDTA, pH 7.8). The gel was run at 2.5 V/cm for 40 min.
Standards for Quantitative Real-Time PCR (TaqMan) Analysis. Two types of DNA standard were used for quantitative estimates of transcript abundances: plasmid cDNA clones and gene-specific PCR products.
cDNA plasmid clones corresponding to the following transcripts were generously provided by the cited authors: MDR1 (Chen et al., 1997),
MRP1 (Cole et al., 1992), MRP2 (GenBank accession number U49248, direct
submission by Kool et al., 1997), MRP3 (Kool et al., 1999), MRP5
(McAleer et al., 1999), BCRP (Doyle et al., 1998), and LRP (Scheffer et
al., 1995). A plasmid harboring the MDR3 cDNA was purchased from ATCC.
Plasmids were propagated using standard procedures and isolated using
the QIAfilter Plasmid midi kit (QIAGEN).
cDNA fragments (see Table 1 and 2)
corresponding to MRP4 (accession number AF071202), MRP6 (accession
number AF076622), villin (accession number X12901),
and CYP3A4 (accession number M14096) that
covered the TaqMan primer/probe area were PCR-amplified from
reverse-transcribed Caco-2 cell RNA using the QIAGEN OneStep RT-PCR
kit. A PCR product corresponding to ABCB5 (accession number AC002486) was generated from genomic Caco-2 DNA using the
HotStarTaq DNA polymerase kit (QIAGEN). All PCR products were purified
using the GenElute PCR DNA purification kit (Sigma, St. Louis, MO).
|
|
Gene-Specific PCR. Gene-specific PCR-primers (Table 1) were developed by performing a multiple sequence alignment within each of the different gene subfamilies using the Clustal W program, available through the Biology WorkBench (http://workbench.sdsc.edu/). Primers were constructed using the PRIMER3 software, also available through the Biology WorkBench and selected based on the multiple sequence alignments. All of the PCR primers were manufactured by Interactiva (Ulm, Germany).
Gene-specific RT-PCR was carried out on total RNA from filter-grown Caco-2 cells using a master mix based on the QIAGEN OneStep RT-PCR kit, supplemented with 12.5 U of SUPERase-In (Ambion, Austin, TX) and 200 ng of total RNA per 25-µl reaction. For each RT-PCR reaction, appropriate primers were added to give a final concentration of 600 nM each primer. Following an initial gene-specific reverse transcription step, each of the reactions went through an initial PCR cycle at an annealing temperature of 56°C, after which the different reactions went through an additional 24 to 34 cycles, depending on the prevalence of the transcript in question, at an elevated annealing temperature (62°C). Thermal cycling was conducted using an UNO II thermocycler from Biometra (Göttingen, Germany). The RNA samples were not contaminated by genomic DNA, as was shown by omitting the reverse transcription step from otherwise identical reactions. Furthermore, no cross-reactivity was observed during PCR amplification when using the different plasmids described above [see Standards for Quantitative Real-Time PCR (TaqMan) Analysis] as controls. We observed expression from all genes except ABCB5 using total RNA from filter-cultured Caco-2 cells (data not shown). Furthermore, all PCR fragments except MDR3 migrated as a single product of the expected size on an agarose gel. PCR products corresponding to the MDR3 transcript migrated as a double band, both having approximately the same intensity, one fragment of the expected size and one slightly larger. Since no expression of ABCB5 was observed, the ABCB5 PCR product was amplified from genomic DNA and used as a DNA standard for the TaqMan analysis.Real-Time Quantitative PCR (TaqMan) Analysis of Transcript Abundance. Suitable gene-specific primer/probe combinations (Table 2) were selected, based on multiple sequence alignments described above (see Gene-Specific PCR), using the Primer Express software (Applied Biosystems, Foster City, CA). TaqMan probes were obtained from Applied Biosystems.
The TaqMan analysis was carried out using 1.5 µg of total RNA, which was reverse transcribed in a 100-µl reaction using random hexamers and the TaqMan reverse transcription reagent (Applied Biosystems). From this, 25 ng of reverse-transcribed RNA was used for each 25-µl TaqMan reaction. The different TaqMan assays were performed using a master mix based on the TaqMan universal PCR master mix (Applied Biosystems). This mix contained the appropriate primer/probe combination. Each primer and probe was used at final concentrations of 300 and 200 nM, respectively. The appropriate reverse-transcribed RNA was added to aliquots of this master mix. These aliquots were subsequently split into duplicate samples (unless otherwise indicated) and run on the ABI PRISM 7700 sequence detection system (Applied Biosystems). TaqMan readings were normalized using the number of villin transcripts determined for each biopsy. This was accomplished by using one of the biopsies as a standard and calculating the ratio between the numbers of villin transcripts determined for the standard and for the biopsy in question. For each biopsy, this ratio was subsequently multiplied with the number of transcripts determined for the gene in question (e.g., MDR1biopsy · villinstandard/villinbiopsy). Villin was chosen since, in the intestine, villin and at least MDR1, MRP1, MRP2, and CYP3A4 are exclusively expressed in the epithelial cells (Thiebaut et al., 1987; West et al., 1988; Kolars et al., 1994;
Peng et al., 1999; Fromm et al., 2000). Furthermore, villin has
previously been established as a useful measure to control for
variation in the enterocyte content of biopsies (Lown et al., 1997).
| |
Results |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
Conclusions
References
|
|---|
Quantitative Analysis of Efflux Protein Transcript Levels in Human
Jejunum.
All of the efflux protein genes except
ABCB5 were expressed in the
human jejunum (Table 3 and Fig. 1).
Indeed, the transcript level for six of the efflux proteins were
comparable with and even higher than that of the hitherto most
intensively studied efflux protein, MDR1. Transcripts coding for BCRP
and MRP2 were expressed at higher levels than the MDR1
transcripts, whereas MDR3 transcripts were only detected at
a very low level. In total, transcript levels spanned a range of three
logs, with the following ranking: BCRP MRP2 > MDR1 MRP3 MRP6 MRP5 MRP1 > MRP4 > MDR3. Also, substantial amounts of both LRP and
CYP3A4 transcripts were detected in the RNA from human
jejunal biopsies.
|
|
Statistical Analysis of Interindividual Variation in MDR1
Expression.
Since an average difference of two in duodenal MDR1
expression seemed sufficient for affecting digoxin plasma levels
(Hoffmeyer et al., 2000), it was of interest to determine the extent to
which variations in transcript copy numbers can be attributed to
interindividual variations and how much are experimental errors
inherent in the TaqMan assay. For this purpose, we performed three
independent TaqMan assays using the same reverse-transcribed total RNA
to investigate the MDR1 transcript copy numbers of the
different jejunal biopsies. The three data sets did not result in
entirely consistent rankings of the individual biopsies with respect to MDR1 expression (Fig. 2), which shows
that at least some of the variation is due to experimental errors.
Nevertheless, one-way analysis of variance and Tukey's multiple
comparison test indicated that 66% of the observed variation could be
attributed to the variation between individuals.
|
Evaluation of the Caco-2 Cell versus Human Jejunum.
In
general, the extent of the expression of the genes responsible for the
efflux systems in filter-grown Caco-2 cell monolayers was in good
agreement with that in the human jejunum (Table 3 and Fig.
3). A comparison of villin-normalized
data indicated that the expression of these genes in Caco-2 cells
generally differed by a factor of less than 2.5 from that in the
jejunum. The exception was BCRP, which exhibited a 100-fold lower
transcript copy number in the Caco-2 cells than in the human jejunum.
Thus, if BCRP is excluded, there is a very good linear correlation
(r2 = 0.90) between the expression of
nine of ten efflux protein transcripts in Caco-2 cells and the human
jejunum.
|
).
| |
Discussion |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
Conclusions
References
|
|---|
Quantitative Analysis of Efflux Protein Transcript Levels in Human
Jejunum.
To our knowledge, this is the first investigation that
describes the quantitative expression of 10 efflux protein transcripts (both apically and basolaterally localized ones) in normal human jejunum, the primary site of absorption of orally administered drugs.
Surprisingly, six of ten of the efflux protein transcripts were
expressed at levels comparable with, and in the case of BCRP and MRP2 even higher than, the MDR1 transcript.
MDR1 is the hitherto most intensively investigated efflux protein.
Since there is clear evidence that many clinically important drugs are
substrates for MDR1 and that polymorphisms in this gene affect the
pharmacokinetics of digoxin (Hoffmeyer et al., 2000), a drug with a
very narrow therapeutic window, our results suggest that increased
attention should now be given to several other abundantly expressed
efflux systems in the small intestine.
; Doyle et al., 1998; Fromm et al., 2000;
Maliepaard et al., 2001). Furthermore, almost none of these studies
were concerned with jejunum, which is the quantitatively most important
drug absorption site of the human small intestine. The exceptions are
MDR1 and MRP2 for which expression was demonstrated in human and rat
jejunum, respectively (Thiebaut et al., 1987; Gotoh et al., 2000;
Mottino et al., 2000).
The MDR1, MDR3, MRP2, and BCRP proteins are all located at the apical
part of the plasma membrane of polarized cells such as epithelia
(Thiebaut et al., 1987; van Helvoort et al., 1996; Fromm et al., 2000;
Jonker et al., 2000). If the comparatively high mRNA expressions of
BCRP and MRP2 are reflected in high levels of
protein, it will most certainly have bearing on the interpretation of
drug absorption of orally administered drugs that are substrates for
these proteins. Indeed, intestinal expression of BCRP in mice results
in a lower bioavailability of orally administered topotecan (Jonker et
al., 2000). Also, in vivo data obtained using MRP2-defective rats
indicate that MRP2 may be involved in intestinal drug efflux (Gotoh et
al., 2000).
The substrate specificities of the efflux proteins partly overlap, and
a complex picture is emerging in which several drug transport and
efflux routes may be active in parallel (Chen et al., 2000; Litman et
al., 2000). For example, in addition to topotecan, BCRP confers
resistance to, or reduced accumulation of, important drugs such as
mitoxantrone, doxorubicin, daunorubicin, prazosin, and bisantrene
(Doyle et al., 1998; Litman et al., 2000), and many of the BCRP
substrates are also substrates of MDR1 (Ambudkar et al., 1999).
However, at least mitoxantrone and topotecan might be better substrates
for BCRP (Litman et al., 2000). Furthermore, although both topotecan
and prazosin are administered orally, BCRP is only a major determinant
of oral bioavailability of topotecan (Jonker et al., 2000). Prazosin,
on the other hand, is well absorbed through the intestine (Hoffman and
Lefkowitz, 1996), which indicates that active efflux (through either
BCRP or MDR1) is not a major determinant of the bioavailability of this compound.
The MRP1, MRP3, MRP5, and MRP6 proteins seem to be basolaterally
localized (Roelofsen et al., 1997; Kool et al., 1999; Madon et al.,
2000; Wijnholds et al., 2000). We found relatively high expression
levels of these transcripts in human normal jejunum, particularly for
the MRP3 transcript. However, we cannot find any published
evidence on the role of these efflux proteins in drug absorption. It
therefore remains to be elucidated whether or not the intestinal
expression of these basolaterally localized efflux proteins can
influence the absorption of orally administered drugs.
The LRP protein, which constitutes a part of the multicomponent vault
complexes, is frequently overexpressed in multidrug-resistant cancer
cells and may mediate drug resistance via a transport process (Scheffer
et al., 1995). We included the LRP protein in this study for this
reason. However, the role of LRP in drug resistance is far from clear,
and it is possible that LRP is only linked to the up-regulation of
other processes involved in multidrug resistance. The LRP
gene is located close to the chromosomal region of MRP (MRP1 and MRP6) and a gene for a protein kinase C
that is involved in the up-regulation of MDR1 activity (Scheffer et
al., 1995). Clearly, further studies on the functional role of LRP are
needed before the significance of the present findings can be established.
Interindividual Variation in the Expression of Multidrug Resistance-Related Genes in Human Jejunum. The interindividual variation in transcript abundance was low for all investigated genes except MDR3, with a difference between the highest and lowest value of around a factor of 2. The higher variability of MDR3 expression might be caused by the existence of alternative transcripts, as is observed in the RNA from filter-grown Caco-2 cells (see Gene-specific PCR under Materials and Methods). This was, however, not investigated.
We conclude that at least some of the observed variation is due to interindividual variation in transcript abundance but the present data set does not allow a reliable ranking of the different individuals (see Statistical Analysis of Interindividual Variation in MDR1 Expression). Among these 13 individuals, no extreme phenotype can be found for any of the genes investigated. Interindividual variations in expression of up to 10-fold (Lown et al., 1995, 1997) and up to
65-fold (Hoffmeyer et al., 2000) have been reported for MDR1, and up to
30-fold for CYP3A4 (Wacher et al., 1998). Still, interindividual
variation in CYP3A4 expression for most of the subjects was
considerably more modest (Lown et al., 1997; Fontana et al., 1999), as
is also reported in this communication. This is also the case for MDR1.
Nevertheless, the homozygous 3435T allele is associated with a 2-fold
reduced MDR1 expression and an increased digoxin plasma concentration
following oral administration (Hoffmeyer et al., 2000).
A parallel investigation of interindividual variability in the
expression of MDR1 and CYP3A4 proteins, and possibly other proteins
(e.g., BCRP), is warranted because of the overlap in substrate use
between these proteins, and because metabolism by intestinal CYP3A4 is
a major determinant of the bioavailability of orally administered drugs
(Wacher et al., 1998). Only in this way will the real impact of MDR1 to
interpatient variability in oral drug bioavailability be established.
Evaluation of the Caco-2 Cell versus Human Jejunum. A comparison of villin-normalized data indicated that the expression of efflux protein genes in Caco-2 cells generally differed by a factor of less than 2.5 from that in the jejunum, a result that is comparable with the interindividual variations observed in this and other studies (vide supra). The exception was BCRP.
However, functional studies have indicated a larger efflux of MDR1 substrates in Caco-2 cells than in the human intestine, which could, thus, be interpreted as an overexpression of MDR1 in Caco-2 cells (Yee, 1997; Gres et al., 1998). Our results challenge this interpretation and
are further corroborated by a recent study of MDR1-mediated efflux of
digoxin and vinblastin across Caco-2 cell monolayers and human and rat
intestinal segments (Stephens et al., 2001). Stephens et al. (2001)
suggests that it may be possible to predict small intestinal drug
efflux quantitatively using Caco-2 cells. However, the variable
expression of MDR1 reported for various Caco-2 clones and culturing
conditions (Delie and Rubas, 1997) suggests that transcript levels in
other Caco-2 clones may not correlate as well with human jejunum as the
results presented here. Indeed, preliminary results indicate some
variability in the MDR1 expression level, both within and between
Caco-2 clones (J. Taipalensuu, unpublished observation). Nevertheless,
our data seems to fit rather well with the Northern blot analysis of
MRP2, MRP3, and MRP5 expression in Caco-2 cells presented by Hirohashi et al. (2000). In the case of MRP1, however, there seems to be a
discrepancy between data. This discrepancy might simply be a result of
the different methods used (TaqMan versus Northern blot analysis) or,
more likely, caused by Caco-2 clone heterogeneity.
| |
Conclusions |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
Conclusions
References
|
|---|
This study indicates that several efflux proteins are abundantly expressed in the healthy human jejunum. In particular, BCRP and MRP2 are more extensively expressed than MDR1, and the roles of these two drug efflux proteins as barriers to intestinal drug absorption are most likely more important than has previously been suspected. Since the substrate specificities of BCRP and MRP2 partly overlap with that of MDR1, it is clear that all of these efflux systems will contribute to a greater or lesser extent to the absorption of such substrates. Furthermore, the results indicate that the Caco-2 cells capture the expression of investigated drug efflux systems, with the exception of BCRP, of the healthy human jejunum. It may therefore be beneficial to complement a Caco-2-based drug efflux screening model with a system that expresses BCRP to cover all important drug efflux systems in the human jejunum. The findings of this study need to be verified at the protein and functional levels.
| |
Acknowledgments |
|---|
Birgitta Hammarlund and Elisabeth Lindgren are gratefully acknowledged for excellent technical assistance with taking biopsies from the small bowel.
| |
Footnotes |
|---|
Accepted for publication June 29, 2001.
Received for publication May 14, 2001.
This work was supported by grants from The Swedish Medical Research Council (Grant 9478), The Swedish National Board for Laboratory Animals (Grant 01-56), and Pharmacia, Sweden.
Address correspondence to: Prof. Per Artursson, Department of Pharmacy, Uppsala University, P.O. Box 580, SE-751 23 Uppsala, Sweden. E-mail: Per.Artursson{at}galenik.uu.se
| |
Abbreviations |
|---|
ABC, ATP-binding cassette; BCRP, breast cancer resistance protein; LRP, lung resistance-related protein; PCR, polymerase chain reaction; RT-PCR, reverse transcription-PCR.
| |
References |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
Conclusions
References
|
|---|
A Practical Approach (Shaw A ed) pp 111-133,
IRL Press at Oxford University Press, Oxford, UK.fact or myth.
Pharm Res (NY)
14:
763-766[Medline].
This article has been cited by other articles:
|
|
 |
|
  A Lehotzky, N Tokesi, I Gonzalez-Alvarez, V Merino, M Bermejo, F Orosz, P Lau, G.G Kovacs, and J Ovadi Progress in the development of early diagnosis and a drug with unique pharmacology to improve cancer therapy Phil Trans R Soc A, October 13, 2008; 366(1880): 3599 - 3617. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H Nevala, T Ylikomi, and H Tahti Evaluation of the selected barrier properties of retinal pigment epithelial cell line ARPE-19 for an in-vitro blood-brain barrier model Human and Experimental Toxicology, October 1, 2008; 27(10): 741 - 749. [Abstract] [PDF]
|
|
|
|
 |
|
 W. Brand, P. A. I. van der Wel, M. J. Rein, D. Barron, G. Williamson, P. J. van Bladeren, and I. M. C. M. Rietjens Metabolism and Transport of the Citrus Flavonoid Hesperetin in Caco-2 Cell Monolayers Drug Metab. Dispos., September 1, 2008; 36(9): 1794 - 1802. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. MacLean, U. Moenning, A. Reichel, and G. Fricker Closing the Gaps: A Full Scan of the Intestinal Expression of P-Glycoprotein, Breast Cancer Resistance Protein, and Multidrug Resistance-Associated Protein 2 in Male and Female Rats Drug Metab. Dispos., July 1, 2008; 36(7): 1249 - 1254. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Meinl, B. Ebert, H. Glatt, and A. Lampen Sulfotransferase Forms Expressed in Human Intestinal Caco-2 and TC7 Cells at Varying Stages of Differentiation and Role in Benzo[a]pyrene Metabolism Drug Metab. Dispos., February 1, 2008; 36(2): 276 - 283. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Poquet, M. N. Clifford, and G. Williamson Transport and Metabolism of Ferulic Acid through the Colonic Epithelium Drug Metab. Dispos., January 1, 2008; 36(1): 190 - 197. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Williamson, I. Aeberli, L. Miguet, Z. Zhang, M.-B. Sanchez, V. Crespy, D. Barron, P. Needs, P. A. Kroon, H. Glavinas, et al. Interaction of Positional Isomers of Quercetin Glucuronides with the Transporter ABCC2 (cMOAT, MRP2) Drug Metab. Dispos., August 1, 2007; 35(8): 1262 - 1268. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Hilgendorf, G. Ahlin, A. Seithel, P. Artursson, A.-L. Ungell, and J. Karlsson Expression of Thirty-six Drug Transporter Genes in Human Intestine, Liver, Kidney, and Organotypic Cell Lines Drug Metab. Dispos., August 1, 2007; 35(8): 1333 - 1340. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Yamagata, H. Kusuhara, M. Morishita, K. Takayama, H. Benameur, and Y. Sugiyama Improvement of the Oral Drug Absorption of Topotecan through the Inhibition of Intestinal Xenobiotic Efflux Transporter, Breast Cancer Resistance Protein, by Excipients Drug Metab. Dispos., July 1, 2007; 35(7): 1142 - 1148. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Lai, L. Xing, G. I. Poda, and Y. Hu Structure-Activity Relationships for Interaction with Multidrug Resistance Protein 2 (ABCC2/MRP2): The Role of Torsion Angle for a Series of Biphenyl-Substituted Heterocycles Drug Metab. Dispos., June 1, 2007; 35(6): 937 - 945. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Cao, X. Chen, J. Liang, X.-Q. Yu, A.-L. Xu, E. Chan, D. Wei, M. Huang, J.-Y. Wen, X.-Y. Yu, et al. Role of P-glycoprotein in the Intestinal Absorption of Glabridin, an Active Flavonoid from the Root of Glycyrrhiza glabra Drug Metab. Dispos., April 1, 2007; 35(4): 539 - 553. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Q. Xia, N. Liu, G. T. Miwa, and L.-S. Gan Interactions of Cyclosporin A with Breast Cancer Resistance Protein Drug Metab. Dispos., April 1, 2007; 35(4): 576 - 582. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. E. Swales, M. Korbonits, R. Carpenter, D. T. Walsh, T. D. Warner, and D. Bishop-Bailey The farnesoid x receptor is expressed in breast cancer and regulates apoptosis and aromatase expression. Cancer Res., October 15, 2006; 66(20): 10120 - 10126. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Sai, Y. Kaneko, S. Ito, K. Mitsuoka, Y. Kato, I. Tamai, P. Artursson, and A. Tsuji PREDOMINANT CONTRIBUTION OF ORGANIC ANION TRANSPORTING POLYPEPTIDE OATP-B (OATP2B1) TO APICAL UPTAKE OF ESTRONE-3-SULFATE BY HUMAN INTESTINAL CACO-2 CELLS Drug Metab. Dispos., August 1, 2006; 34(8): 1423 - 1431. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P Hruz, C Zimmermann, H Gutmann, L Degen, U Beuers, L Terracciano, J Drewe, and C Beglinger Adaptive regulation of the ileal apical sodium dependent bile acid transporter (ASBT) in patients with obstructive cholestasis Gut, March 1, 2006; 55(3): 395 - 402. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. L.A. Plasschaert, E. S.J.M. de Bont, M. Boezen, D. M. vander Kolk, S. M.J.G. Daenen, K. N. Faber, W. A. Kamps, E. G.E. de Vries, and E. Vellenga Expression of Multidrug Resistance-Associated Proteins Predicts Prognosis in Childhood and Adult Acute Lymphoblastic Leukemia Clin. Cancer Res., December 15, 2005; 11(24): 8661 - 8668. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. E. Taub, L. Podila, D. Ely, and I. Almeida FUNCTIONAL ASSESSMENT OF MULTIPLE P-GLYCOPROTEIN (P-GP) PROBE SUBSTRATES: INFLUENCE OF CELL LINE AND MODULATOR CONCENTRATION ON P-GP ACTIVITY Drug Metab. Dispos., November 1, 2005; 33(11): 1679 - 1687. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Imai, M. Imoto, H. Sakamoto, and M. Hashimoto IDENTIFICATION OF ESTERASES EXPRESSED IN CACO-2 CELLS AND EFFECTS OF THEIR HYDROLYZING ACTIVITY IN PREDICTING HUMAN INTESTINAL ABSORPTION Drug Metab. Dispos., August 1, 2005; 33(8): 1185 - 1190. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Q. Xia, N. Liu, D. Yang, G. Miwa, and L.-S. Gan EXPRESSION, LOCALIZATION, AND FUNCTIONAL CHARACTERISTICS OF BREAST CANCER RESISTANCE PROTEIN IN CACO-2 CELLS Drug Metab. Dispos., May 1, 2005; 33(5): 637 - 643. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Adachi, H. Suzuki, A. H. Schinkel, and Y. Sugiyama Role of Breast Cancer Resistance Protein (Bcrp1/Abcg2) in the Extrusion of Glucuronide and Sulfate Conjugates from Enterocytes to Intestinal Lumen Mol. Pharmacol., March 1, 2005; 67(3): 923 - 928. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. F. K. Ejendal and C. A. Hrycyna Differential Sensitivities of the Human ATP-Binding Cassette Transporters ABCG2 and P-Glycoprotein to Cyclosporin A Mol. Pharmacol., March 1, 2005; 67(3): 902 - 911. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Zimmermann, H. Gutmann, P. Hruz, J.-P. Gutzwiller, C. Beglinger, and J. Drewe MAPPING OF MULTIDRUG RESISTANCE GENE 1 AND MULTIDRUG RESISTANCE-ASSOCIATED PROTEIN ISOFORM 1 TO 5 mRNA EXPRESSION ALONG THE HUMAN INTESTINAL TRACT Drug Metab. Dispos., February 1, 2005; 33(2): 219 - 224. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. M. Prime-Chapman, R. A. Fearn, A. E. Cooper, V. Moore, and B. H. Hirst Differential Multidrug Resistance-Associated Protein 1 through 6 Isoform Expression and Function in Human Intestinal Epithelial Caco-2 Cells J. Pharmacol. Exp. Ther., November 1, 2004; 311(2): 476 - 484. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. L. von Moltke, B. W. Granda, J. M. Grassi, M. D. Perloff, D. Vishnuvardhan, and D. J. Greenblatt INTERACTION OF TRIAZOLAM AND KETOCONAZOLE IN P-GLYCOPROTEIN-DEFICIENT MICE Drug Metab. Dispos., August 1, 2004; 32(8): 800 - 804. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Gupta, Y. Zhang, J. D. Unadkat, and Q. Mao HIV Protease Inhibitors Are Inhibitors but Not Substrates of the Human Breast Cancer Resistance Protein (BCRP/ABCG2) J. Pharmacol. Exp. Ther., July 1, 2004; 310(1): 334 - 341. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Notenboom, D. S. Miller, P. Smits, F. G. M. Russel, and R. Masereeuw Involvement of guanylyl cyclase and cGMP in the regulation of Mrp2-mediated transport in the proximal tubule Am J Physiol Renal Physiol, July 1, 2004; 287(1): F33 - F38. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Zhang, X. Yang, and M. E. Morris Flavonoids Are Inhibitors of Breast Cancer Resistance Protein (ABCG2)-Mediated Transport Mol. Pharmacol., May 1, 2004; 65(5): 1208 - 1216. [Abstract] [Full Text]
|
|
|
|
 |
|
 A. S. Ray, L. Olson, and A. Fridland Role of Purine Nucleoside Phosphorylase in Interactions between 2',3'-Dideoxyinosine and Allopurinol, Ganciclovir, or Tenofovir Antimicrob. Agents Chemother., April 1, 2004; 48(4): 1089 - 1095. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Depeille, P. Cuq, S. Mary, I. Passagne, A. Evrard, D. Cupissol, and L. Vian Glutathione S-Transferase M1 and Multidrug Resistance Protein 1 Act in Synergy to Protect Melanoma Cells from Vincristine Effects Mol. Pharmacol., April 1, 2004; 65(4): 897 - 905. [Abstract] [Full Text]
|
|
|
|
|
|
A. Harrison, A. Betts, K. Fenner, K. Beaumont, A. Edgington, S. Roffey, J. Davis, P. Comby, and P. Morgan NONLINEAR ORAL PHARMACOKINETICS OF THE {alpha}-ANTAGONIST 4-AMINO-5-(4-FLUOROPHENYL)-6,7-DIMETHOXY-2-[4-(MORPHOLINOCARBONYL)-PERHYDRO-1,4-DIAZEPIN-1-YL]QUINOLINE IN HUMANS: USE OF PRECLINICAL DATA TO RATIONALIZE CLINICAL OBSERVATIONS Drug Metab. Dispos., February 1, 2004; 32(2): 197 - 204. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C G Dietrich, A Geier, and R P J Oude Elferink ABC of oral bioavailability: transporters as gatekeepers in the gut Gut, December 1, 2003; 52(12): 1788 - 1795. [Full Text] [PDF]
|
|
|
|
 |
|
 T. Sugawara, M. Kinoshita, M. Ohnishi, J. Nagata, and M. Saito Digestion of Maize Sphingolipids in Rats and Uptake of Sphingadienine by Caco-2 Cells J. Nutr., September 1, 2003; 133(9): 2777 - 2782. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Mizuno, T. Niwa, Y. Yotsumoto, and Y. Sugiyama Impact of Drug Transporter Studies on Drug Discovery and Development Pharmacol. Rev., September 1, 2003; 55(3): 425 - 461. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. D. Warner and J. A. Mitchell Nonsteroidal antiinflammatory drugs inhibiting prostanoid efflux: As easy as ABC? PNAS, August 5, 2003; 100(16): 9108 - 9110. [Full Text] [PDF]
|
|
|
|
|
|
T. D. Bjornsson, J. T. Callaghan, H. J. Einolf, V. Fischer, L. Gan, S. Grimm, J. Kao, S. P. King, G. Miwa, L. Ni, et al. THE CONDUCT OF IN VITRO AND IN VIVO DRUG-DRUG INTERACTION STUDIES: A PHARMACEUTICAL RESEARCH AND MANUFACTURERS OF AMERICA (PhRMA) PERSPECTIVE Drug Metab. Dispos., July 1, 2003; 31(7): 815 - 832. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Beck, K. Hayashi, B. Nishiguchi, O. Le Saux, M. Hayashi, and C. D. Boyd The Distribution of Abcc6 in Normal Mouse Tissues Suggests Multiple Functions for this ABC Transporter J. Histochem. Cytochem., July 1, 2003; 51(7): 887 - 902. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. D. Bjornsson, J. T. Callaghan, H. J. Einolf, V. Fischer, L. Gan, S. Grimm, J. Kao, S. P. King, G. Miwa, L. Ni, et al. The Conduct of In Vitro and In Vivo Drug-Drug Interaction Studies: A PhRMA Perspective J. Clin. Pharmacol., May 1, 2003; 43(5): 443 - 469. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Lu, X. Meng, C. Li, S. Sang, C. Patten, S. Sheng, J. Hong, N. Bai, B. Winnik, C.-T. Ho, et al. Glucuronides of Tea Catechins: Enzymology of Biosynthesis and Biological Activities Drug Metab. Dispos., April 1, 2003; 31(4): 452 - 461. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. D. Allen, S. C. van Dort, M. Buitelaar, O. van Tellingen, and A. H. Schinkel Mouse Breast Cancer Resistance Protein (Bcrp1/Abcg2) Mediates Etoposide Resistance and Transport, but Etoposide Oral Availability Is Limited Primarily by P-glycoprotein Cancer Res., March 15, 2003; 63(6): 1339 - 1344. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Langmann, R. Mauerer, A. Zahn, C. Moehle, M. Probst, W. Stremmel, and G. Schmitz Real-Time Reverse Transcription-PCR Expression Profiling of the Complete Human ATP-Binding Cassette Transporter Superfamily in Various Tissues Clin. Chem., February 1, 2003; 49(2): 230 - 238. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. N. Johnson, A. Rostami-Hodjegan, J. M. Goddard, M. S. Tanner, and G. T. Tucker Contribution of midazolam and its 1-hydroxy metabolite to preoperative sedation in children: a pharmacokinetic-pharmacodynamic analysis Br. J. Anaesth., September 1, 2002; 89(3): 428 - 437. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. R. Luo, P. V. Paranjpe, A. Guo, E. Rubin, and P. Sinko Intestinal Transport of Irinotecan in Caco-2 Cells and MDCK II Cells Overexpressing Efflux Transporters Pgp, cMOAT, and MRP1 Drug Metab. Dispos., July 1, 2002; 30(7): 763 - 770. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Liu and M. Hu Absorption and Metabolism of Flavonoids in the Caco-2 Cell Culture Model and a Perused Rat Intestinal Model Drug Metab. Dispos., April 1, 2002; 30(4): 370 - 377. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. D. Allen and A. H. Schinkel Multidrug Resistance and Pharmacological Protection Mediated by the Breast Cancer Resistance Protein (BCRP/ABCG2) Mol. Cancer Ther., April 1, 2002; 1(6): 427 - 434. [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 |
 |
 |
|
 |
 |
 |
