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Hitoshi Endou - One of the best experts on this subject based on the ideXlab platform.

  • A novel human Organic Anion Transporter NPT4 mediates the transport of ochratoxin A.
    Journal of pharmacological sciences, 2011
    Co-Authors: Promsuk Jutabha, Hitoshi Endou, Naohiko Anzai, Keitaro Hayashi, Mariko Domae, Kohsuke Uchida, Hiroyuki Sakurai
    Abstract:

    Abstract. In the present study, we investigated the transport of nephrotoxic mycotoxin ochratoxin A (OTxA) by a novel human Organic Anion Transporter hNPT4 using the Xenopus oocyte expression system. hNPT4 mediated time- and concentration-dependent uptake of OTxA (K m : 802.8 μ M) in a pH- and voltage-sensitive manner. Cis -inhibition experiments suggest that the substrate selectivity of hNPT4 is similar to that of hOAT4. The fact that the K m of OTxA for the efflux Transporter hNPT4 was much higher than those for the uptake Transporters hOAT1 and hOAT3 may favor the accumulation of OTxA in the tubular cell and lead to nephrotoxicity.

  • Novel liver-specific Organic Anion Transporter OAT7 that operates the exchange of sulfate conjugates for short chain fatty acid butyrate†
    Hepatology (Baltimore Md.), 2007
    Co-Authors: Ho Jung Shin, Hitoshi Endou, Kyung Kim, Naohiko Anzai, Atsushi Enomoto, Yoshikatsu Kanai
    Abstract:

    The liver plays an important role in the elimination of endogenous and exogenous lipophilic Organic compounds from the body, which is mediated by various carrier proteins that differ in substrate specificity and kinetic properties. Here, we have characterized a novel member of the Organic Anion Transporter family (SLC22) isolated from human liver. The Transporter named Organic Anion Transporter 7 (OAT7/ SLC22A9) showed 35% to 46% identities to those of other Organic Anion Transporters of SLC22 family. When expressed in Xenopus oocytes, OAT7 mediated Na+-independent, high-affinity transport of sulfate-conjugated steroids, estrone sulfate (ES; Km = 8.7 μM), and dehydroepiandrosterone sulfate (Km = 2.2 μM). In addition, OAT7 interacted with negatively charged sulfobromophthalein, indocyanine green, and several sulfate-conjugated xenobiotics. In contrast, glucuronide and glutathione conjugates exhibited no inhibitory effects on OAT7-mediated [3H]ES transport. OAT7-mediated [3H]ES transport was trans-stimulated by three-carbon to five-carbon (C3 to C5) short-chain fatty acids. The efflux of [14C]butyrate (C4) via OAT7 was significantly trans-stimulated by extracellular ES. Furthermore, OAT7 mediated [14C]butyrate uptake and [3H]ES efflux in exchange for extracellular butyrate both in Xenopus oocytes and OAT7-stably expressing cells. OAT7 protein was localized in the sinusoidal membrane of hepatocytes by immunohistochemical analysis. Conclusion: OAT7 is the first liver-specific Transporter among members of the Organic Anion Transporters of SLC22 family. Our findings suggest a new class of substrates for Organic Anion Transporters and provide evidence for the transport of Anionic substances such as sulfate-conjugates in exchange for butyrate in hepatocytes. (HEPATOLOGY 2007;45:1046–1055.)

  • Transport of 99mTc-MAG3 via Rat Renal Organic Anion Transporter 1
    Journal of nuclear medicine : official publication Society of Nuclear Medicine, 2004
    Co-Authors: Naoto Shikano, Yoshikatsu Kanai, Keiichi Kawai, Nobuyoshi Ishikawa, Hitoshi Endou
    Abstract:

    Recently, complementary DNA (cDNA) encoding a p-aminohippurate (PAH) Transporter designated rat Organic Anion Transporter 1 (OAT1) was isolated. OAT1, a multispecific Organic Anion Transporter at the basolateral membrane, is exclusively expressed in the middle segment of the proximal tubule in the rat kidney. It has been proposed that OAT1 is indirectly involved in PAH uptake via the Na+ dicarboxylate coTransporter. In this study, in molecular biologic experiments using OAT1-expressing Xenopus laevis oocytes, we obtained evidence that 99mTc-mercaptoacetylglycylglycylglycine (MAG3) is transported via OAT1. Methods: Capped OAT1 complementary RNA (cRNA) was synthesized from library plasmid cDNA linearized with BamHI using in vitro transcription. Defolliculated oocytes were injected with 10 ng of OAT1 cRNA. Two to 3 d after injection, uptake of 99mTc-MAG3 was measured using ND96 solution containing 18.5 kBq of 99mTc-MAG3. Before the uptake experiments, OAT1-expressing oocytes were preincubated for 2 h with 1 mmol/L glutarate (a dicarboxylate), to generate an outwardly directed glutarate gradient. Then, after incubation for 60 min at room temperature, radioactivity of oocytes was determined. For the inhibition experiments, uptake was assessed in the absence or presence of inhibitor: 2 mmol/L of PAH, o-iodohippurate (OIH), probenecid, 3,5-diiodo-4-pyridone-N-acetate (iodopyracet), furosemide, ethacrynic acid, glucoheptonate, maleic acid, l-Tyr, or tetraethylammonium (TEA) or 0.1 mmol/L of 2,4-dinitrophenol (DNP). Results: Na+ had a significant effect on 99mTc-MAG3 uptake (P

  • Isolation, Characterization and Differential Gene Expression of Multispecific Organic Anion Transporter 2 in Mice
    Molecular pharmacology, 2002
    Co-Authors: Yasuna Kobayashi, Takashi Sekine, Hitoshi Endou, Naomi Ohshiro, Akiko Shibusawa, Tadanori Sasaki, Shogo Tokuyama, Toshinori Yamamoto
    Abstract:

    We isolated cDNA encoding a multispecific Organic Anion Transporter 2 (OAT2) from the mouse kidney cDNA library. Isolated mouse OAT2 (mOAT2) consisted of 1623 base pairs that encoded a 540-amino acid residue protein with 12 putative membrane-spanning domains, and the amino acid sequence was 87% identical to that of rat OAT2 (rOAT2). The gene coding for mOAT2, Slc22a7, is found on chromosome 17C. Northern blot analysis revealed that the mOAT2 mRNA is abundantly expressed in the male mouse kidney, whereas it was predominantly expressed in both the liver and kidney of female mice. When expressed in Xenopus laevis oocytes, mOAT2 mediated the high affinity transport of glutarate (K(m) = 15.8 +/- 3.2 microM) and prostaglandin E2 (K(m) = 5.2 +/- 0.5 nM) in a sodium-independent manner. mOAT2-expressing oocytes also mediated the uptake of alpha-ketoglutarate, glutarate, prostaglandin E2, p-aminohippuric acid, methotrexate, ochratoxin A, valproate, and allopurinol. However, we did not observe mOAT2-mediated uptake of salicylate. A wide range of structurally unrelated Organic Anions inhibited mOAT2-mediated glutarate uptake especially erythromycin, a potent inhibitor. These results indicate that isolated mOAT2 is a multispecific Organic Anion Transporter having some differences in substrate specificity compared with rOAT2. In addition, we found that there exists a sex- and species-related differential gene expression of the OAT2 isoform.

  • role of human Organic Anion Transporter 4 in the transport of ochratoxin a
    Biochimica et Biophysica Acta, 2002
    Co-Authors: Ellappan Babu, Takashi Sekine, Seok Ho Cha, Michio Takeda, Akihiro Tojo, Atsushi Enomoto, Shinichi Narikawa, Yukari Kobayashi, Dhanapal Sakthisekaran, Hitoshi Endou
    Abstract:

    Abstract The purpose of this study was to investigate the characteristics of ochratoxin A (OTA) transport by multispecific human Organic Anion Transporter 4 (hOAT4) using mouse proximal tubule cells stably transfected with hOAT4 (S 2 hOAT4). Immunohistochemical analysis revealed that hOAT4 protein was localized to the apical side of the proximal tubule. S 2 hOAT4 expressed hOAT4 protein in the apical side as well as basolateral side and the cells were cultured on the plastic dish for experiments. S 2 hOAT4 exhibited a time- and concentration-dependent, and a saturable increase in OTA uptake, with an apparent K m value of 22.9±2.44 μM. The OTA uptakes were inhibited by several substrates for the OATs. Probenecid, piroxicam, octanoate and citrinin inhibited OTA uptake by hOAT4 in a competitive manner ( K i =44.4–336.4 μM), with the following order of potency: probenecid>piroxicam>octanoate>citrinin. The efflux of OTA by S 2 hOAT4 was higher than that by mock. Addition of OTA resulted in slight decrease in viability of S 2 hOAT4 compared with mock. These results indicate that hOAT4 mediates the high-affinity transport of OTA on the apical side of the proximal tubule, whereas the transport characteristics of OTA are distinct from those by basolateral OATs.

Douglas H. Sweet - One of the best experts on this subject based on the ideXlab platform.

  • Cumulative Organic Anion Transporter-Mediated Drug-Drug Interaction Potential of Multiple Components in Salvia Miltiorrhiza (Danshen) Preparations
    Pharmaceutical research, 2014
    Co-Authors: Li Wang, Jürgen Venitz, Douglas H. Sweet
    Abstract:

    Purpose To evaluate Organic Anion Transporter-mediated drug-drug interaction (DDI) potential for individual active components of Danshen (Salvia miltiorrhiza) vs. combinations using in vitro and in silico approaches.

  • the anthraquinone drug rhein potently interferes with Organic Anion Transporter mediated renal elimination
    Biochemical Pharmacology, 2013
    Co-Authors: Li Wang, Xiaolei Pan, Douglas H. Sweet
    Abstract:

    Abstract Rhein, a major metabolite of the prodrug diacerein and a major component of the medicinal herb Rheum sp., is used for its beneficial effects in a variety of clinical applications including the treatment of osteoarthritis and diabetic nephropathy. The physicochemical properties of rhein are consistent with those of known Organic Anion Transporter (OAT) substrates and inhibitors. Therefore, the inhibitory effect of rhein on human (h) OAT1, hOAT3, hOAT4, and murine (m) Oat1 and mOat3 was examined in heterologous cell lines stably expressing each Transporter in isolation. Rhein was shown to potently inhibit hOAT1 and hOAT3, with IC50 estimates in the low nanomolar range (IC50 = 77.1 ± 5.5 nM and 8.4 ± 2.5 nM, respectively), while poor affinity was observed for hOAT4 (IC50 > 100 μM). Marked species differences were observed with hOAT1 and hOAT3 exhibiting 3- and 28-fold higher affinity for rhein as compared to their murine orthologs. The estimated drug–drug interaction (DDI) indices (≫0.1) indicated a very strong potential for clinically relevant, rhein perpetrated DDIs mediated by inhibition of hOAT1 (DDI index = 5.0; 83% inhibition) and/or hOAT3 (DDI index = 46; 98% inhibition) transport activity. These results suggested that rhein, from herbal medicines and/or prodrug conversion, may significantly impact the dosing, efficacy and toxicity (i.e., pharmacokinetics and pharmacodynamics) of co-administered hOAT1 and/or hOAT3 drug substrates.

  • Organic Anion Transporter 3 oat3 slc22a8 interacts with carboxyfluoroquinolones and deletion increases systemic exposure to ciprofloxacin
    Molecular Pharmacology, 2008
    Co-Authors: Adam L Vanwert, Chutima Srimaroeng, Douglas H. Sweet
    Abstract:

    Carboxyfluoroquinolones, such as ciprofloxacin, are used for the treatment of numerous infectious diseases. Renal secretion is a major determinant of their systemic and urinary concentration, but the specific Transporters involved are virtually unknown. In vivo studies implicate the Organic Anion Transporter (OAT) family as a pivotal component of carboxyfluoroquinolone renal secretion. Therefore, this study identified the specific renal basolateral OAT(s) involved, thereby highlighting potential sources of carboxyfluoroquinolone-drug interactions and variable efficacy. Two heterologous expression systems, Xenopus laevis oocytes and cell monolayers, were used to determine the roles of murine and human renal basolateral mOat1/hOAT1 and mOat3/hOAT3. Ciprofloxacin was transported by mOat3 in both systems (Km value, 70 ± 6 μM) and demonstrated no interaction with mOat1 or hOAT1. Furthermore, ciprofloxacin, norfloxacin, ofloxacin, and gatifloxacin exhibited concentration-dependent inhibition of transport on mOat3 in cells with inhibition constants of 198 ± 39, 558 ± 75, 745 ± 165, and 941 ± 232 μM, respectively. Ciprofloxacin and gatifloxacin also inhibited hOAT3. Thereafter, in vivo elimination of ciprofloxacin was assessed in wild-type and Oat3 null mice [Oat3(-/-)]. Oat3(-/-) mice exhibited significantly elevated plasma levels of ciprofloxacin at clinically relevant concentrations (P

  • Organic Anion Transporter 3 oat3 slc22a8 knockout mice exhibit altered clearance and distribution of penicillin g
    American Journal of Physiology-renal Physiology, 2007
    Co-Authors: Adam L Vanwert, Rachel M Bailey, Douglas H. Sweet
    Abstract:

    The interaction of renal basolateral Organic Anion Transporter 3 (Oat3) with commonly used pharmacotherapeutics (e.g., NSAIDs, β-lactams, and methotrexate) has been studied extensively in vitro. Ho...

  • Organic Anion Transporter 3 (Oat3/Slc22a8) knockout mice exhibit altered clearance and distribution of penicillin G
    American journal of physiology. Renal physiology, 2007
    Co-Authors: Adam L Vanwert, Rachel M Bailey, Douglas H. Sweet
    Abstract:

    The interaction of renal basolateral Organic Anion Transporter 3 (Oat3) with commonly used pharmacotherapeutics (e.g., NSAIDs, β-lactams, and methotrexate) has been studied extensively in vitro. Ho...

Yuichi Sugiyama - One of the best experts on this subject based on the ideXlab platform.

  • transcriptional regulation of human and mouse Organic Anion Transporter 1 by hepatocyte nuclear factor 1 α β
    Journal of Pharmacology and Experimental Therapeutics, 2008
    Co-Authors: Takami Saji, Hiroyuki Kusuhara, Ryota Kikuchi, Insook Kim, Frank J Gonzalez, Yuichi Sugiyama
    Abstract:

    Organic Anion Transporter 1 (OAT1/ SLC22A6 ) is predominantly expressed in the proximal tubules of the kidney. Cumulative studies have shown its critical role in the tubular secretion of a variety of Organic Anions, including several clinically important drugs. In addition, OAT1 is also involved in the pharmacological effect of diuretics and the nephrotoxicity of antiviral drugs. In contrast to these functional characterizations, the regulatory mechanism of OAT1 expression is poorly understood. It was recently demonstrated that the expression of Oat1 was markedly reduced in the kidneys of hepatocyte nuclear factor 1α (Hnf1α)-null mice. However, in vitro evidence for the involvement of HNF1α and further analyses are required to illustrate the transcriptional regulation of OAT1 genes in more detail. Computational analysis of the potential transcription factor binding sites revealed that the HNF1-motif was conserved in the proximal-promoter region of human and mouse OAT1 genes. The mRNA expression of mouse Organic Anion Transporter 1 was drastically reduced in Hnf1α-null mice compared with that in wild-type mice, which was consistent with a previous report ([Maher et al., 2006][1]). Forced expression of HNF1α alone or both HNF1α and HNF1β enhanced the activity of human and mouse OAT1 promoters in the transactivation assays, whereas HNF1β alone was not active. Mutations in the HNF1-motif significantly reduced this transactivation. Direct binding of HNF1α/HNF1α homodimer and HNF1α/HNF1β heterodimer to the HNF1-motif found in the human OAT1 promoter was demonstrated by electrophoretic mobility shift assays. These results provide convincing evidence for the involvement of HNF1α/β in the constitutive expression of human and mouse OAT1 in the kidney. [1]: #ref-19

  • involvement of rat Organic Anion Transporter 3 roat3 in cephaloridine induced nephrotoxicity in comparison with roat1
    Life Sciences, 2002
    Co-Authors: Kyu Yong Jung, Michio Takeda, Akihiro Tojo, Arthit Chairoungdua, Hiroyuki Kusuhara, Do Kyung Kim, Minoru Shimoda, Shinichi Narikawa, Bong Kyu Choi, Yuichi Sugiyama
    Abstract:

    This study was performed to elucidate the possible involvement of Organic Anion Transporter 3 (OAT3) in cephaloridine (CER)-induced nephrotoxicity and compare the substrate specificity between rOAT3 and rat OAT1 (rOAT1) for various cephalosporin antibiotics, using proximal tubule cells stably expressing rOAT3 (S2 rOAT3) and rOAT1 (S2 rOAT1). S2 rOAT3 exhibited a CER uptake and a higher susceptibility to CER cytotoxicity than did mock, which was recovered by probenecid. Various cephalosporin antibiotics significantly inhibited both estrone sulfate uptake in S2 rOAT3 and para-aminohippuric acid uptake in S2 rOAT1. The Ki values of CER, cefoperazone, cephalothin and cefazolin for rOAT3- and rOAT1-mediated Organic Anion transport ranged from 0.048 to 1.14 mM and from 0.48 to 1.32 mM, respectively. These results suggest that rOAT3, at least in part, mediates CER uptake and CER-induced nephrotoxicity as rOAT1. There was some difference of affinity between rOAT3 and rOAT1 for cephalosporin antibiotics.

  • Physicochemical Parameters Responsible for the Affinity of Methotrexate Analogs for Rat Canalicular Multispecific Organic Anion Transporter (cMOAT/MRP2)
    Pharmaceutical Research, 2001
    Co-Authors: Yukio Kato, Masayuki Haramura, Masateru Ohta, Hiroharu Matsuoka, Yuichi Sugiyama
    Abstract:

    Purpose . Canalicular multispecific Organic Anion Transporter (cMOAT/MRP2) is known to exhibit a broad substrate specificity toward amphiphatic Organic Anions, including methotrexate (MTX). The present study aims to identify the physicochemical properties of MTX derivatives that correlate with recognition specificity by cMOAT/MRP2. Methods . We examined the inhibitory effect of MTX and 24 analogs on the transport of [^3H]–S–(2,4–dinitrophenyl)glutathione by cMOAT/MRP2. The affinity constants of these compounds were compared with their physicochemical parameters. The primary active transport of several compounds was also confirmed. Results . The affinity constants closely correlated with the octanol/water partition coefficient (clogP), and a linear combination of polar and nonpolar surface areas. The affinity for cMOAT/MRP2 also closely correlated with the molecular weight, which also showed a significant correlation with nonpolar surface area and clogP. Conclusions . Recognition by cMOAT/MRP2 depends on a balance of dynamic surface properties between the polar and nonpolar regions of MTX analogs. The so–called “molecular weight threshold” for the cMOAT/MRP2 affinity of these compounds can be explained by their physicochemical parameters, especially their nonpolar surface areas.

  • Physicochemical parameters responsible for the affinity of methotrexate analogs for rat canalicular multispecific Organic Anion Transporter (cMOAT/MRP2).
    Pharmaceutical research, 2001
    Co-Authors: Yong–hae Han, Masayuki Haramura, Masateru Ohta, Hiroharu Matsuoka, Yukio Kato, Yuichi Sugiyama
    Abstract:

    Purpose. Canalicular multispecific Organic Anion Transporter (cMOAT/MRP2) is known to exhibit a broad substrate specificity toward amphiphatic Organic Anions, including methotrexate (MTX). The present study aims to identify the physicochemical properties of MTX derivatives that correlate with recognition specificity by cMOAT/MRP2.

  • molecular cloning and characterization of multispecific Organic Anion Transporter 4 expressed in the placenta
    Journal of Biological Chemistry, 2000
    Co-Authors: Seok Ho Cha, Yuichi Sugiyama, Takashi Sekine, Yoshikatsu Kanai, Ju Young Kim, Hiroyuki Kusuhara, Do Kyung Kim, Hitoshi Endou
    Abstract:

    Abstract A cDNA encoding a novel multispecific Organic Anion Transporter, OAT4, was isolated from a human kidney cDNA library. The OAT4 cDNA consisted of 2210 base pairs that encoded a 550-amino acid residue protein with 12 putative membrane-spanning domains. The amino acid sequence of OAT4 showed 38 to 44% identity to those of other members of the OAT family. Northern blot analysis revealed that OAT4 mRNA is abundantly expressed in the placenta as well as in the kidney. When expressed in Xenopus oocytes, OAT4 mediated the high affinity transport of estrone sulfate (K m = 1.01 μm) and dehydroepiandrosterone sulfate (K m = 0.63 μm) in a sodium-independent manner. OAT4 also mediated the transport of ochratoxin A. OAT4-mediated transport of estrone sulfate was inhibited by several sulfate conjugates, such asp-nitrophenyl sulfate, α-naphthyl sulfate, β-estradiol sulfate, and 4-methylumbelliferyl sulfate. By contrast, glucuronide conjugates showed little or no inhibitory effect on the OAT4-mediated transport of estrone sulfate. OAT4 interacted with chemically heterogeneous Anionic compounds, such as nonsteroidal anti-inflammatory drugs, diuretics, sulfobromophthalein, penicillin G, and bile salts, whereas tetraethylammonium, an Organic cation, did not. OAT4 is the first member of the multispecific Organic Anion Transporter family, which is expressed abundantly in the placenta. OAT4 might be responsible for the elimination and detoxification of harmful Anionic substances from the fetus.

Takashi Sekine - One of the best experts on this subject based on the ideXlab platform.

  • Isolation, Characterization and Differential Gene Expression of Multispecific Organic Anion Transporter 2 in Mice
    Molecular pharmacology, 2002
    Co-Authors: Yasuna Kobayashi, Takashi Sekine, Hitoshi Endou, Naomi Ohshiro, Akiko Shibusawa, Tadanori Sasaki, Shogo Tokuyama, Toshinori Yamamoto
    Abstract:

    We isolated cDNA encoding a multispecific Organic Anion Transporter 2 (OAT2) from the mouse kidney cDNA library. Isolated mouse OAT2 (mOAT2) consisted of 1623 base pairs that encoded a 540-amino acid residue protein with 12 putative membrane-spanning domains, and the amino acid sequence was 87% identical to that of rat OAT2 (rOAT2). The gene coding for mOAT2, Slc22a7, is found on chromosome 17C. Northern blot analysis revealed that the mOAT2 mRNA is abundantly expressed in the male mouse kidney, whereas it was predominantly expressed in both the liver and kidney of female mice. When expressed in Xenopus laevis oocytes, mOAT2 mediated the high affinity transport of glutarate (K(m) = 15.8 +/- 3.2 microM) and prostaglandin E2 (K(m) = 5.2 +/- 0.5 nM) in a sodium-independent manner. mOAT2-expressing oocytes also mediated the uptake of alpha-ketoglutarate, glutarate, prostaglandin E2, p-aminohippuric acid, methotrexate, ochratoxin A, valproate, and allopurinol. However, we did not observe mOAT2-mediated uptake of salicylate. A wide range of structurally unrelated Organic Anions inhibited mOAT2-mediated glutarate uptake especially erythromycin, a potent inhibitor. These results indicate that isolated mOAT2 is a multispecific Organic Anion Transporter having some differences in substrate specificity compared with rOAT2. In addition, we found that there exists a sex- and species-related differential gene expression of the OAT2 isoform.

  • role of human Organic Anion Transporter 4 in the transport of ochratoxin a
    Biochimica et Biophysica Acta, 2002
    Co-Authors: Ellappan Babu, Takashi Sekine, Seok Ho Cha, Michio Takeda, Akihiro Tojo, Atsushi Enomoto, Shinichi Narikawa, Yukari Kobayashi, Dhanapal Sakthisekaran, Hitoshi Endou
    Abstract:

    Abstract The purpose of this study was to investigate the characteristics of ochratoxin A (OTA) transport by multispecific human Organic Anion Transporter 4 (hOAT4) using mouse proximal tubule cells stably transfected with hOAT4 (S 2 hOAT4). Immunohistochemical analysis revealed that hOAT4 protein was localized to the apical side of the proximal tubule. S 2 hOAT4 expressed hOAT4 protein in the apical side as well as basolateral side and the cells were cultured on the plastic dish for experiments. S 2 hOAT4 exhibited a time- and concentration-dependent, and a saturable increase in OTA uptake, with an apparent K m value of 22.9±2.44 μM. The OTA uptakes were inhibited by several substrates for the OATs. Probenecid, piroxicam, octanoate and citrinin inhibited OTA uptake by hOAT4 in a competitive manner ( K i =44.4–336.4 μM), with the following order of potency: probenecid>piroxicam>octanoate>citrinin. The efflux of OTA by S 2 hOAT4 was higher than that by mock. Addition of OTA resulted in slight decrease in viability of S 2 hOAT4 compared with mock. These results indicate that hOAT4 mediates the high-affinity transport of OTA on the apical side of the proximal tubule, whereas the transport characteristics of OTA are distinct from those by basolateral OATs.

  • rat multispecific Organic Anion Transporter 1 roat1 transports zidovudine acyclovir and other antiviral nucleoside analogs
    Journal of Pharmacology and Experimental Therapeutics, 2000
    Co-Authors: Saiko Wada, Takashi Sekine, Seok Ho Cha, Minoru Tsuda, Yoshikatsu Kanai, Miyako Kimura, Hitoshi Endou
    Abstract:

    Organic Anion Transporter 1 (OAT1) is a p -aminohippurate/dicarboxylate exchanger that plays a primary role in the tubular secretion of endogenous and exogenous Organic Anions. OAT1 is located in the basolateral membrane of the proximal tubular cells and mediates the uptake of various Organic Anions from the peritubular fluid. In this study, we investigated the transport of antiviral nucleoside analogs via rat OAT1 (rOAT1) using a heterologous expression system in Xenopus laevis oocytes. Oocytes injected with rOAT1 cRNA showed significantly higher uptake of zidovudine (AZT) and acyclovir (ACV) than control oocytes. rOAT1-mediated uptake of AZT and ACV was probenecid-sensitive and increased by the outwardly directed gradient of glutarate. The affinity of rOAT1 for AZT and ACV was determined to be 68 and 242 μM, respectively. Five other antiviral agents that we studied (zalcitabine, didanosine, lamivudine, stavudine, and trifluridine) were also shown to be transported by rOAT1, whereas foscarnet, a phosphate analog, was not. The aforementioned nucleoside analogs lack a typical Anionic group and are not very hydrophobic. This study demonstrates extension of the substrate spectrum of rOAT1 and provides a molecular basis for the pharmacokinetics of antiviral nucleoside analogs.

  • molecular cloning and characterization of multispecific Organic Anion Transporter 4 expressed in the placenta
    Journal of Biological Chemistry, 2000
    Co-Authors: Seok Ho Cha, Yuichi Sugiyama, Takashi Sekine, Yoshikatsu Kanai, Ju Young Kim, Hiroyuki Kusuhara, Do Kyung Kim, Hitoshi Endou
    Abstract:

    Abstract A cDNA encoding a novel multispecific Organic Anion Transporter, OAT4, was isolated from a human kidney cDNA library. The OAT4 cDNA consisted of 2210 base pairs that encoded a 550-amino acid residue protein with 12 putative membrane-spanning domains. The amino acid sequence of OAT4 showed 38 to 44% identity to those of other members of the OAT family. Northern blot analysis revealed that OAT4 mRNA is abundantly expressed in the placenta as well as in the kidney. When expressed in Xenopus oocytes, OAT4 mediated the high affinity transport of estrone sulfate (K m = 1.01 μm) and dehydroepiandrosterone sulfate (K m = 0.63 μm) in a sodium-independent manner. OAT4 also mediated the transport of ochratoxin A. OAT4-mediated transport of estrone sulfate was inhibited by several sulfate conjugates, such asp-nitrophenyl sulfate, α-naphthyl sulfate, β-estradiol sulfate, and 4-methylumbelliferyl sulfate. By contrast, glucuronide conjugates showed little or no inhibitory effect on the OAT4-mediated transport of estrone sulfate. OAT4 interacted with chemically heterogeneous Anionic compounds, such as nonsteroidal anti-inflammatory drugs, diuretics, sulfobromophthalein, penicillin G, and bile salts, whereas tetraethylammonium, an Organic cation, did not. OAT4 is the first member of the multispecific Organic Anion Transporter family, which is expressed abundantly in the placenta. OAT4 might be responsible for the elimination and detoxification of harmful Anionic substances from the fetus.

  • The multispecific Organic Anion Transporter (OAT) family.
    Pflugers Archiv : European journal of physiology, 2000
    Co-Authors: Takashi Sekine, Seok Ho Cha, Hitoshi Endou
    Abstract:

    Organic Anion Transporters play important roles in the elimination of a variety of endogenous substances, xenobiotics and their metabolites from the body. During the last decade, molecular cloning has identified several families of multispecific Organic Anion Transporters mediating the renal and hepatic elimination of Organic Anions and, most recently, the OAT (Organic Anion Transporter) family, the founding member of which (OAT1) is the basolateral p-aminohippurate (PAH) Transporter in the renal proximal tubule. So far, four isoforms have been identified. OATs are membrane proteins with 12 putative membrane-spanning domains and function as sodium-independent exchangers or facilitators. OATs show weak structural similarity to Organic cation Transporters (OCTs) and OCTN/carnitine Transporters. OATs are multispecific Organic Anion Transporters, the substrates of which include both endogenous (e.g. cyclic nucleotides, prostaglandins, urate, dicarboxylates) and exogenous Anions (various Anionic drugs and environmental substances). All members of the OAT family are expressed in the kidney, while some are also expressed in the liver, brain and placenta. The OAT family represents the renal secretory pathway for Organic Anions and is also involved in the distribution of Organic Anions in the body.

Yoshikatsu Kanai - One of the best experts on this subject based on the ideXlab platform.

  • Novel liver-specific Organic Anion Transporter OAT7 that operates the exchange of sulfate conjugates for short chain fatty acid butyrate†
    Hepatology (Baltimore Md.), 2007
    Co-Authors: Ho Jung Shin, Hitoshi Endou, Kyung Kim, Naohiko Anzai, Atsushi Enomoto, Yoshikatsu Kanai
    Abstract:

    The liver plays an important role in the elimination of endogenous and exogenous lipophilic Organic compounds from the body, which is mediated by various carrier proteins that differ in substrate specificity and kinetic properties. Here, we have characterized a novel member of the Organic Anion Transporter family (SLC22) isolated from human liver. The Transporter named Organic Anion Transporter 7 (OAT7/ SLC22A9) showed 35% to 46% identities to those of other Organic Anion Transporters of SLC22 family. When expressed in Xenopus oocytes, OAT7 mediated Na+-independent, high-affinity transport of sulfate-conjugated steroids, estrone sulfate (ES; Km = 8.7 μM), and dehydroepiandrosterone sulfate (Km = 2.2 μM). In addition, OAT7 interacted with negatively charged sulfobromophthalein, indocyanine green, and several sulfate-conjugated xenobiotics. In contrast, glucuronide and glutathione conjugates exhibited no inhibitory effects on OAT7-mediated [3H]ES transport. OAT7-mediated [3H]ES transport was trans-stimulated by three-carbon to five-carbon (C3 to C5) short-chain fatty acids. The efflux of [14C]butyrate (C4) via OAT7 was significantly trans-stimulated by extracellular ES. Furthermore, OAT7 mediated [14C]butyrate uptake and [3H]ES efflux in exchange for extracellular butyrate both in Xenopus oocytes and OAT7-stably expressing cells. OAT7 protein was localized in the sinusoidal membrane of hepatocytes by immunohistochemical analysis. Conclusion: OAT7 is the first liver-specific Transporter among members of the Organic Anion Transporters of SLC22 family. Our findings suggest a new class of substrates for Organic Anion Transporters and provide evidence for the transport of Anionic substances such as sulfate-conjugates in exchange for butyrate in hepatocytes. (HEPATOLOGY 2007;45:1046–1055.)

  • Transport of 99mTc-MAG3 via Rat Renal Organic Anion Transporter 1
    Journal of nuclear medicine : official publication Society of Nuclear Medicine, 2004
    Co-Authors: Naoto Shikano, Yoshikatsu Kanai, Keiichi Kawai, Nobuyoshi Ishikawa, Hitoshi Endou
    Abstract:

    Recently, complementary DNA (cDNA) encoding a p-aminohippurate (PAH) Transporter designated rat Organic Anion Transporter 1 (OAT1) was isolated. OAT1, a multispecific Organic Anion Transporter at the basolateral membrane, is exclusively expressed in the middle segment of the proximal tubule in the rat kidney. It has been proposed that OAT1 is indirectly involved in PAH uptake via the Na+ dicarboxylate coTransporter. In this study, in molecular biologic experiments using OAT1-expressing Xenopus laevis oocytes, we obtained evidence that 99mTc-mercaptoacetylglycylglycylglycine (MAG3) is transported via OAT1. Methods: Capped OAT1 complementary RNA (cRNA) was synthesized from library plasmid cDNA linearized with BamHI using in vitro transcription. Defolliculated oocytes were injected with 10 ng of OAT1 cRNA. Two to 3 d after injection, uptake of 99mTc-MAG3 was measured using ND96 solution containing 18.5 kBq of 99mTc-MAG3. Before the uptake experiments, OAT1-expressing oocytes were preincubated for 2 h with 1 mmol/L glutarate (a dicarboxylate), to generate an outwardly directed glutarate gradient. Then, after incubation for 60 min at room temperature, radioactivity of oocytes was determined. For the inhibition experiments, uptake was assessed in the absence or presence of inhibitor: 2 mmol/L of PAH, o-iodohippurate (OIH), probenecid, 3,5-diiodo-4-pyridone-N-acetate (iodopyracet), furosemide, ethacrynic acid, glucoheptonate, maleic acid, l-Tyr, or tetraethylammonium (TEA) or 0.1 mmol/L of 2,4-dinitrophenol (DNP). Results: Na+ had a significant effect on 99mTc-MAG3 uptake (P

  • Identification of a Novel Voltage-driven Organic Anion Transporter Present at Apical Membrane of Renal Proximal Tubule
    The Journal of biological chemistry, 2003
    Co-Authors: Promsuk Jutabha, Yoshikatsu Kanai, Makoto Hosoyamada, Arthit Chairoungdua, Kyung Kim, Yuji Iribe, Ellappan Babu, Ju Young Kim, Naohiko Anzai, Varanuj Chatsudthipong
    Abstract:

    A novel transport protein with the properties of voltage-driven Organic Anion transport was isolated from pig kidney cortex by expression cloning in Xenopus laevis oocytes. A cDNA library was constructed from size-fractionated poly(A)+ RNA and screened for p-aminohippurate (PAH) transport in high potassium medium. A 1856-base pair cDNA encoding a 467-amino acid peptide designated as OATV1 (voltage-driven Organic Anion Transporter 1) was isolated. The predicted amino acid sequence of OATV1 exhibited 60-65% identity to those of human, rat, rabbit, and mouse sodium-dependent phosphate coTransporter type 1 (NPT1), although OATV1 did not transport phosphate. The homology of this Transporter to known members of the Organic Anion Transporter family (OAT family) was about 25-30%. OATV1-mediated PAH transport was affected by the changes in membrane potential. The transport was Na+-independent and enhanced at high concentrations of extracellular potassium and low concentrations of extracellular chloride. Under the voltage clamp condition, extracellularly applied PAH induced outward currents in oocytes expressing OATV1. The current showed steep voltage dependence, consistent with the voltage-driven transport of PAH by OATV1. The PAH transport was inhibited by various Organic Anions but not by Organic cations, indicating the multispecific nature of OATV1 for Anionic compounds. This transport protein is localized at the apical membrane of renal proximal tubule, consistent with the proposed localization of a voltage-driven Organic Anion Transporter. Therefore, it is proposed that OATV1 plays an important role to excrete drugs, xenobiotics, and their metabolites driven by membrane voltage through the apical membrane of the tubular epithelial cells into the urine.

  • rat multispecific Organic Anion Transporter 1 roat1 transports zidovudine acyclovir and other antiviral nucleoside analogs
    Journal of Pharmacology and Experimental Therapeutics, 2000
    Co-Authors: Saiko Wada, Takashi Sekine, Seok Ho Cha, Minoru Tsuda, Yoshikatsu Kanai, Miyako Kimura, Hitoshi Endou
    Abstract:

    Organic Anion Transporter 1 (OAT1) is a p -aminohippurate/dicarboxylate exchanger that plays a primary role in the tubular secretion of endogenous and exogenous Organic Anions. OAT1 is located in the basolateral membrane of the proximal tubular cells and mediates the uptake of various Organic Anions from the peritubular fluid. In this study, we investigated the transport of antiviral nucleoside analogs via rat OAT1 (rOAT1) using a heterologous expression system in Xenopus laevis oocytes. Oocytes injected with rOAT1 cRNA showed significantly higher uptake of zidovudine (AZT) and acyclovir (ACV) than control oocytes. rOAT1-mediated uptake of AZT and ACV was probenecid-sensitive and increased by the outwardly directed gradient of glutarate. The affinity of rOAT1 for AZT and ACV was determined to be 68 and 242 μM, respectively. Five other antiviral agents that we studied (zalcitabine, didanosine, lamivudine, stavudine, and trifluridine) were also shown to be transported by rOAT1, whereas foscarnet, a phosphate analog, was not. The aforementioned nucleoside analogs lack a typical Anionic group and are not very hydrophobic. This study demonstrates extension of the substrate spectrum of rOAT1 and provides a molecular basis for the pharmacokinetics of antiviral nucleoside analogs.

  • molecular cloning and characterization of multispecific Organic Anion Transporter 4 expressed in the placenta
    Journal of Biological Chemistry, 2000
    Co-Authors: Seok Ho Cha, Yuichi Sugiyama, Takashi Sekine, Yoshikatsu Kanai, Ju Young Kim, Hiroyuki Kusuhara, Do Kyung Kim, Hitoshi Endou
    Abstract:

    Abstract A cDNA encoding a novel multispecific Organic Anion Transporter, OAT4, was isolated from a human kidney cDNA library. The OAT4 cDNA consisted of 2210 base pairs that encoded a 550-amino acid residue protein with 12 putative membrane-spanning domains. The amino acid sequence of OAT4 showed 38 to 44% identity to those of other members of the OAT family. Northern blot analysis revealed that OAT4 mRNA is abundantly expressed in the placenta as well as in the kidney. When expressed in Xenopus oocytes, OAT4 mediated the high affinity transport of estrone sulfate (K m = 1.01 μm) and dehydroepiandrosterone sulfate (K m = 0.63 μm) in a sodium-independent manner. OAT4 also mediated the transport of ochratoxin A. OAT4-mediated transport of estrone sulfate was inhibited by several sulfate conjugates, such asp-nitrophenyl sulfate, α-naphthyl sulfate, β-estradiol sulfate, and 4-methylumbelliferyl sulfate. By contrast, glucuronide conjugates showed little or no inhibitory effect on the OAT4-mediated transport of estrone sulfate. OAT4 interacted with chemically heterogeneous Anionic compounds, such as nonsteroidal anti-inflammatory drugs, diuretics, sulfobromophthalein, penicillin G, and bile salts, whereas tetraethylammonium, an Organic cation, did not. OAT4 is the first member of the multispecific Organic Anion Transporter family, which is expressed abundantly in the placenta. OAT4 might be responsible for the elimination and detoxification of harmful Anionic substances from the fetus.