Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 9 de 9
Filter
Add more filters










Database
Language
Publication year range
1.
J Biol Chem ; 279(44): 45942-50, 2004 Oct 29.
Article in English | MEDLINE | ID: mdl-15304510

ABSTRACT

The urate-anion exchanger URAT1 is a member of the organic anion transporter (OAT) family that regulates blood urate level in humans and is targeted by uricosuric and antiuricosuric agents. URAT1 is expressed only in the kidney, where it is thought to participate in tubular urate reabsorption. We found that the multivalent PDZ (PSD-95, Drosophila discs-large protein, Zonula occludens protein 1) domain-containing protein, PDZK1 interacts with URAT1 in a yeast two-hybrid screen. Such an interaction requires the PDZ motif of URAT1 in its extreme intracellular C-terminal region and the first, second, and fourth PDZ domains of PDZK1 as identified by yeast two-hybrid assay, in vitro binding assay and surface plasmon resonance analysis (K(D) = 1.97-514 nM). Coimmunoprecipitation studies revealed that the wild-type URAT1, but not its mutant lacking the PDZ-motif, directly interacts with PDZK1. Colocalization of URAT1 and PDZK1 was observed at the apical membrane of renal proximal tubular cells. The association of URAT1 with PDZK1 enhanced urate transport activities in HEK293 cells (1.4-fold), and the deletion of the URAT1 C-terminal PDZ motif abolished this effect. The augmentation of the transport activity was accompanied by a significant increase in the V(max) of urate transport via URAT1 and was associated with the increased surface expression level of URAT1 protein from HEK293 cells stably expressing URAT1 transfected with PDZK1. Taken together, the present study indicates the novel role of PDZK1 in regulating the functional activity of URAT1-mediated urate transport in the apical membrane of renal proximal tubules.


Subject(s)
Carrier Proteins/physiology , Organic Anion Transporters/physiology , Biological Transport , Carrier Proteins/chemistry , Carrier Proteins/genetics , Cell Line , Humans , Kidney Tubules, Proximal/metabolism , Membrane Proteins , Organic Anion Transporters/chemistry , Organic Anion Transporters/genetics , Organic Cation Transport Proteins , RNA, Messenger/analysis , Uric Acid/metabolism
2.
J Pharmacol Sci ; 94(3): 297-304, 2004 Mar.
Article in English | MEDLINE | ID: mdl-15037815

ABSTRACT

Human organic anion transporter OAT4 is expressed in the kidney and placenta and mediates high-affinity transport of estrone-3-sulfate (E1S). Because a previous study demonstrated no trans-stimulatory effects by E1S, the mode of organic anion transport via OAT4 remains still unclear. In the present study, we examined the driving force of OAT4 using mouse proximal tubular cells stably expressing OAT4 (S2 OAT4). OAT4-mediated E1S uptake was inhibited by glutarate (GA) (IC50:1.25 mM) and [14C]GA uptake via S2 OAT4 was significantly trans-stimulated by unlabeled GA (5 mM) (P<0.001). [3H]E1S uptake via S2 OAT4 was significantly trans-stimulated by preloaded GA (P<0.001) and its [14C]GA efflux was significantly trans-stimulated by unlabeled E1S in the medium (P<0.05). In addition, both the uptake and efflux of [14C]p-aminohippuric acid (PAH) and [14C]GA via S2 OAT4 were significantly trans-stimulated by unlabeled GA or PAH. The immunoreactivities of OAT4 were observed in the apical membrane of proximal tubules along with those of basolateral organic anion/dicarboxylate exchangers such as hOAT1 and hOAT3 in the same tubular population. These results indicate that OAT4 is an apical organic anion/dicarboxylate exchanger and mainly functions as an apical pathway for the reabsorption of some organic anions in renal proximal tubules driven by an outwardly directed dicarboxylate gradient.


Subject(s)
Dicarboxylic Acid Transporters/physiology , Estrone/analogs & derivatives , Kidney Tubules, Proximal/drug effects , Kidney Tubules, Proximal/physiology , Organic Anion Transporters, Sodium-Independent/physiology , Animals , Carbon Radioisotopes , Cells, Cultured , Dicarboxylic Acid Transporters/chemistry , Estrone/antagonists & inhibitors , Estrone/metabolism , Glutarates/metabolism , Glutarates/pharmacology , Humans , Immunohistochemistry , Kidney Tubules, Proximal/cytology , Liver-Specific Organic Anion Transporter 1 , Mice , Organic Anion Transport Protein 1/genetics , Organic Anion Transport Protein 1/metabolism , Organic Anion Transporters, Sodium-Independent/antagonists & inhibitors , Organic Anion Transporters, Sodium-Independent/genetics , Organic Anion Transporters, Sodium-Independent/metabolism , Time Factors , Tritium , Up-Regulation , p-Aminohippuric Acid/metabolism , p-Aminohippuric Acid/pharmacology
3.
J Pharmacol Sci ; 94(2): 197-202, 2004 Feb.
Article in English | MEDLINE | ID: mdl-14978359

ABSTRACT

We have elucidated the interactions of human and rat organic anion transporters (hOATs and rOATs) with pravastatin and cimetidine. Pravastatin inhibited hOAT1/rOAT1, hOAT2/rOAT2, hOAT3/rOAT3, and hOAT4. The mode of inhibition was noncompetitive for hOAT1 and hOAT2, whereas it was competitive for hOAT3 and hOAT4. Cimetidine also inhibited hOAT1/rOAT1, hOAT3/rOAT3, and hOAT4. The mode of inhibition was a combination of competitive and noncompetitive manners for hOAT1, whereas it was competitive for hOAT3. The effects of OAT inhibitors on OAT1, OAT2, and OAT3 exhibited some but not so remarkable interspecies differences between humans and rats. In conclusion, we have characterized pravastatin and cimetidine as OAT inhibitors.


Subject(s)
Cimetidine/pharmacokinetics , Organic Anion Transporters/antagonists & inhibitors , Organic Anion Transporters/metabolism , Pravastatin/pharmacokinetics , Animals , Cimetidine/chemistry , Humans , Pravastatin/chemistry , Rats
4.
Eur J Pharmacol ; 483(2-3): 133-8, 2004 Jan 12.
Article in English | MEDLINE | ID: mdl-14729100

ABSTRACT

The purpose of this study was to elucidate the role of human organic anion transporters (human OATs) in the induction of drug-induced skeletal muscle abnormalities. 3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors have been clinically used for lowering plasma cholesterol levels, and are known to induce various forms of skeletal muscle abnormalities including myopathy and rhabdomyolysis. Immunohistochemical analysis revealed that human OAT1 and human OAT3 are localized in the cytoplasmic membrane of the human skeletal muscles. The activities of human OATs were measured using mouse cell lines from renal proximal tubules stably expressing human OATs. Human OAT3, but not human OAT1, mediates the transport of pravastatin. Fluvastatin inhibited organic anion uptake mediated by human OAT1 in a mixture of competitive and noncompetitive manner, whereas simvastatin and fluvastatin noncompetitively inhibited the organic anion uptake mediated by human OAT3. In conclusion, the organic anion transporters OAT1 and OAT3 are localized in the cytoplasmic membrane of human skeletal muscles. Pravastatin, simvasatin, and fluvasatin inhibit human OATs activity. These results suggest that muscle organic anion transporters play a role in the muscular side effects of HMG-CoA reductase inhibitors.


Subject(s)
Hydroxymethylglutaryl-CoA Reductase Inhibitors/pharmacology , Muscle, Skeletal/drug effects , Organic Anion Transporters/antagonists & inhibitors , Organic Anion Transporters/physiology , Adult , Animals , Cells, Cultured , Dose-Response Relationship, Drug , Humans , Male , Mice , Muscle, Skeletal/physiology
5.
Biochem Biophys Res Commun ; 313(3): 789-93, 2004 Jan 16.
Article in English | MEDLINE | ID: mdl-14697261

ABSTRACT

Organic cation transporter OCT1 (SLC22A1) plays an essential role in absorption, distribution, and excretion of various xenobiotics including therapeutically important drugs. In the present study, we analyzed the functional properties of the single nucleotide polymorphisms (SNPs) in SLC22A1 gene found in Japanese control individuals. Four mutations resulting in the amino acid changes (F160L, P283L, R287G, and P341L) were functionally characterized in Xenopus oocyte expression system. Two new SNPs, identified in Japanese population, P283L and R287G exhibited no uptake of both [14C]TEA and [3H]MPP+, although their protein expressions were detected in the plasma membrane of the oocytes injected with their cRNAs. Uptake of [14C]TEA by P341L was reduced to 65.1% compared to wild type, whereas F160L showed no significant change in its transport activity. This study suggests that the newly found OCT1 variants will contribute to inter-individual variations leading to the differences in cationic drug disposition and perhaps certain disease processes.


Subject(s)
Organic Cation Transporter 1/genetics , Polymorphism, Single Nucleotide , Animals , Biological Transport , Cations , Cell Membrane/metabolism , DNA, Complementary/metabolism , Dose-Response Relationship, Drug , Humans , Japan , Kinetics , Microscopy, Fluorescence , Models, Biological , Mutagenesis, Site-Directed , Mutation , Oocytes/metabolism , Polymorphism, Genetic , Potassium Channel Blockers/pharmacology , RNA, Complementary/metabolism , Tetraethylammonium/chemistry , Xenopus
6.
Eur J Pharmacol ; 466(1-2): 13-20, 2003 Apr 11.
Article in English | MEDLINE | ID: mdl-12679137

ABSTRACT

Various uremic toxicants including indoxyl sulfate exert a number of biological effects on uremic patients. In order to elucidate the molecular mechanisms for the pharmacokinetics of indoxyl sulfate in human, we examined the interactions of human organic anion transporters (human-OATs) and human organic cation transporters (human-OCTs) with indoxyl sulfate using stable transfectants. Indoxyl sulfate inhibited human-OAT1, human-OAT3 and human-OAT4, but not human-OAT2, human-OCT1 and human-OCT2. Kinetic analysis revealed that the K(i) values for human-OAT1, human-OAT3 and human-OAT4 were 22.7, 168.7 and 181.3 microM, respectively. Human-OAT1 and human-OAT3 mediated the uptake of indoxyl sulfate and human-OAT4 mediated not only the uptake but also the efflux of indoxyl sulfate. In conclusion, by comparing the K(i) values with the plasma concentration of unbound indoxyl sulfate, it was predicted that human-OAT1 and human-OAT3 mediate the transport of indoxyl sulfate in vivo. In addition, it was suggested that human-OAT1 and human-OAT3 are involved in the urinary excretion of indoxyl sulfate, the exacerbation of renal dysfunction and the induction of uremic encephalopathy by indoxyl sulfate.


Subject(s)
Cation Transport Proteins/metabolism , Indican/pharmacokinetics , Organic Anion Transporters, Sodium-Independent/metabolism , Animals , Biological Transport , Cells, Cultured , Humans , Indican/blood , Indican/urine , Kidney Tubules, Proximal/cytology , Organic Anion Transport Protein 1/metabolism , Rats , Solute Carrier Organic Anion Transporter Family Member 1B3
7.
Eur J Pharmacol ; 465(1-2): 1-7, 2003 Mar 28.
Article in English | MEDLINE | ID: mdl-12650826

ABSTRACT

Cephalosporin antibiotics are thought to be excreted into the urine via organic anion transporters (OATs) and OAT can mediate nephrotoxicity by cephalosporins, particularly by cephaloridine. The purpose of this study was to elucidate the interaction of human-OAT2 and rat-OAT2 with cephalosporin antibiotics using proximal tubule cells stably expressing human-OAT2 and rat-OAT2. Human-OAT2 is localized to the basolateral side of the proximal tubule, whereas rat-OAT2 is localized to the apical side of the proximal tubule. Cephalosporins tested were cephalothin, cefoperazone, cefazolin, ceftriaxone, cephaloridine, cefotaxime, cefadroxil and cefamandole. These cephalosporins dose-dependently inhibited organic anion uptake mediated by human-OAT2 and rat-OAT2. There was no species difference observed for the effects of OAT2 with cephalosporins between human and rat transporters. Kinetic analysis revealed that the inhibitory effects for human-OAT2 were competitive. Cephaloridine significantly decreased the viability of cells stably expressing human-OAT2, human-OAT1, human-OAT3 and human-OAT4. The decreased viability of cells stably expressing human-OAT1, human-OAT3 and human-OAT4 but not human-OAT2 was reversed by probenecid. In conclusion, human-OAT2 interacts with cephalosporins, and thus, human-OAT2 may mediate the uptake of cephalosporins on the basolateral side of the proximal tubule. The interaction of human-OAT2 with cephalosporins was the weakest among the basolateral human-OATs tested. In addition, it is suggested that human-OATs mediate cephaloridine-induced nephrotoxicity.


Subject(s)
Anti-Bacterial Agents/pharmacology , Cephalosporins/pharmacology , Organic Anion Transporters, Sodium-Independent/metabolism , Animals , Biological Transport/drug effects , Cefadroxil/pharmacology , Cefamandole/pharmacology , Cefazolin/pharmacology , Cefoperazone/pharmacology , Cefotaxime/pharmacology , Ceftriaxone/pharmacology , Cell Line , Cell Survival/drug effects , Cephaloridine/pharmacology , Cephalothin/pharmacology , Dinoprost/pharmacokinetics , Dose-Response Relationship, Drug , Humans , Kinetics , Mice , Mice, Transgenic , Organic Anion Transporters, Sodium-Independent/genetics , Probenecid/pharmacology , Rats , Transfection , Uricosuric Agents/pharmacology
8.
J Pharmacol Sci ; 93(4): 430-6, 2003 Dec.
Article in English | MEDLINE | ID: mdl-14737013

ABSTRACT

The purpose of the present study was to elucidate the expression of human organic anion transporter 1 (hOAT1) and hOAT3 in the choroid plexus of the human brain and their interactions with neurotransmitter metabolites using stable cell lines. Immunohistochemical analysis revealed that hOAT1 and hOAT3 are expressed in the cytoplasmic membrane and cytoplasm of human choroid plexus. Neurotransmitter metabolites, namely, 5-methoxyindole-3-acetic acid (5-MI-3-AA), homovanillic acid (HVA), vanilmandelic acid (VMA), 3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindole-3-acetic acid (5-HI-3-AA), N-acetyl-5-hydroxytryptamine (NA-5-HTT), melatonin, 5-methoxytryptamine (5-MTT), 3,4-dihidroxymandelic acid (DHMA), 5-hydroxytryptophol, and 5-methoxytryptophol (5-MTP), but not methanephrine (MN), normethanephrine (NMN), and 3-methyltyramine (3-MT), at 2 mM, inhibited para-aminohippuric acid uptake mediated by hOAT1. On the other hand, melatonin, 5-MI-3-AA, NA-5-HTT, 5-MTT, 5-MTP, HVA, 5-HI-3-AA, VMA, DOPAC, 5-hydroxytryptophol, and MN, but not 3-MT, DHMA, and NMN, at 2 mM, inhibited estrone sulfate uptake mediated by hOAT3. Differences in the IC(50) values between hOAT1 and hOAT3 were observed for DHMA, DOPAC, HVA, 5-HI-3-AA, melatonin, 5-MI-3-AA, 5-MTP, 5-MTT, and VMA. HOAT1 and hOAT3 mediated the transport of VMA but not HVA and melatonin. These results suggest that hOAT1 and hOAT3 are involved in the efflux of various neurotransmitter metabolites from the cerebrospinal fluid to the blood across the choroid plexus.


Subject(s)
Choroid Plexus/metabolism , Neurotransmitter Agents/metabolism , Organic Anion Transport Protein 1/metabolism , Organic Anion Transporters, Sodium-Independent/metabolism , Cell Line , Homovanillic Acid/metabolism , Humans , Melatonin/metabolism , Organic Anion Transport Protein 1/genetics , Organic Anion Transport Protein 1/physiology , Organic Anion Transporters, Sodium-Independent/genetics , Organic Anion Transporters, Sodium-Independent/physiology , Vanilmandelic Acid/metabolism
9.
J Pharmacol Exp Ther ; 303(2): 534-9, 2002 Nov.
Article in English | MEDLINE | ID: mdl-12388633

ABSTRACT

The purpose of this study was to elucidate the interactions of human organic anion transporters (hOATs) and human organic cation transporters (hOCTs) with nonsteroidal anti-inflammatory drugs (NSAIDs) using cells stably expressing hOATs and hOCTs. NSAIDs tested were acetaminophen, acetylsalicylate, salicylate, diclofenac, ibuprofen, indomethacin, ketoprofen, mefenamic acid, naproxen, piroxicam, phenacetin, and sulindac. These NSAIDs inhibited organic anion uptake mediated by hOAT1, hOAT2, hOAT3, and hOAT4. By comparing the IC(50) values of NSAIDs for hOATs, it was found that hOAT1 and hOAT3 exhibited higher affinity interactions with NSAIDs than did hOAT2 and hOAT4. HOAT1, hOAT2, hOAT3, and hOAT4 mediated the uptake of either ibuprofen, indomethacin, ketoprofen, or salicylate, but not acetylsalicylate. Although organic cation uptake mediated by hOCT1 and hOCT2 was also inhibited by some NSAIDs, hOCT1 and hOCT2 did not mediate the uptake of NSAIDs. In conclusion, hOATs and hOCTs interacted with various NSAIDs, whereas hOATs but not hOCTs mediated the transport of some of these NSAIDs. Considering the localization of hOATs, it was suggested that the interactions of hOATs with NSAIDs are associated with the pharmacokinetics and the induction of adverse reactions of NSAIDs.


Subject(s)
Alprostadil/analogs & derivatives , Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Organic Anion Transporters/metabolism , Organic Cation Transport Proteins/metabolism , Alprostadil/metabolism , Animals , Anti-Inflammatory Agents, Non-Steroidal/chemistry , Cells, Cultured , Chemical Phenomena , Chemistry, Physical , Dinoprost/metabolism , Humans , Kidney Tubules, Proximal/drug effects , Kidney Tubules, Proximal/metabolism , Mice , Mice, Transgenic , Organic Anion Transporters/antagonists & inhibitors , Organic Cation Transport Proteins/antagonists & inhibitors
SELECTION OF CITATIONS
SEARCH DETAIL
...