scholarly journals Transport of Kynurenic Acid by Rat Organic Anion Transporters rOAT1 and rOAT3: Species Difference between Human and Rat in OAT1

2013 ◽  
Vol 6 ◽  
pp. IJTR.S11206 ◽  
Author(s):  
Yuichi Uwai ◽  
Hiroaki Hara ◽  
Kikuo Iwamoto
Keyword(s):  
Kynurenic Acid ◽  
Organic Anion ◽  
Species Difference ◽  
Xenopus Laevis Oocytes ◽  
Organic Anion Transporters ◽  
Comparative Experiment ◽  
Transport Activity ◽  
Estrone Sulfate ◽  
Anion Transporters ◽  
Uptake Experiment

A tryptophan catabolite, kynurenic acid, is involved in schizophrenia and uremia; there is little information on the mechanism of its disposition. Recently, our laboratory showed that kynurenic acid is a good substrate of human organic anion transporters hOAT1 and hOAT3. In this study, we performed uptake experiment using Xenopus laevis oocytes to characterize the transport of kynurenic acid by rat homologs of the transporters, rOAT1, and rOAT3. These transporters stimulated the uptake of kynurenic acid into oocytes, and transport by rOAT3 was marked. The Km values of the transport were estimated to be 8.46 μM for rOAT1 and 4.81 μM for rOAT3, and these values are comparable to their human homologs. The transport activity of kynurenic acid by rOAT1 was about one quarter of that of p-aminohippurate, although they were at the similar levels in hOAT1. A comparative experiment with hOAT1 was added in this study, showing that uptake amounts of kynurenic acid by hOAT1-expressing oocytes were 4 times greater than rOAT1-expressing oocytes. rOAT3 transported kynurenic acid as efficiently as estrone sulfate; this phenomenon was also observed in hOAT3. In conclusion, transport of kynurenic acid by rOAT1 and rOAT3 was shown. The characteristics of rOAT3 were similar to hOAT3, but low transport activity of kynurenic acid by rOAT1 was exhibited compared with hOAT1.

Human organic anion transporter 1B1 and 1B3 function as bidirectional carriers and do not mediate GSH-bile acid cotransport

2007 ◽  
Vol 293 (1) ◽  
pp. G271-G278 ◽  
Author(s):  
Chitrawina Mahagita ◽  
Steven M. Grassl ◽  
Pawinee Piyachaturawat ◽  
Nazzareno Ballatori
Keyword(s):  
Bile Acid ◽  
Transport Mechanism ◽  
Organic Anion ◽  
Large Family ◽  
Organic Anion Transporter ◽  
Xenopus Laevis Oocytes ◽  
Facilitated Diffusion ◽  
Transport Activity ◽  
Estrone Sulfate ◽  
Anion Transporter

Organic anion transporting polypeptides (OATP/ SLCO) are generally believed to function as electroneutral anion exchangers, but direct evidence for this contention has only been provided for one member of this large family of genes, rat Oatp1a1/Oatp1 ( Slco1a1). In contrast, a recent study has indicated that human OATP1B3/OATP-8 ( SLCO1B3) functions as a GSH-bile acid cotransporter. The present study examined the transport mechanism and possible GSH requirement of the two members of this protein family that are expressed in relatively high levels in the human liver, OATP1B3/OATP-8 and OATP1B1/OATP-C ( SLCO1B1). Uptake of taurocholate in Xenopus laevis oocytes expressing either OATP1B1/OATP-C, OATP1B3/OATP-8, or polymorphic forms of OATP1B3/OATP-8 (namely, S112A and/or M233I) was cis-inhibited by taurocholate and estrone sulfate but was unaffected by GSH. Likewise, taurocholate and estrone sulfate transport were trans-stimulated by estrone sulfate and taurocholate but were unaffected by GSH. OATP1B3/OATP-8 also did not mediate GSH efflux or GSH-taurocholate cotransport out of cells, indicating that GSH is not required for transport activity. In addition, estrone sulfate uptake in oocytes microinjected with OATP1B3/OATP-8 or OATP1B1/OATP-C cRNA was unaffected by depolarization of the membrane potential or by changes in pH, suggesting an electroneutral transport mechanism. Overall, these results indicate that OATP1B3/OATP-8 and OATP1B1/OATP-C most likely function as bidirectional facilitated diffusion transporters and that GSH is not a substrate or activator of their transport activity.

Transporters involved in renal excretion of N-carbamoylglutamate, an orphan drug to treat inborn n-acetylglutamate synthase deficiency

2014 ◽  
Vol 307 (12) ◽  
pp. F1373-F1379 ◽  
Author(s):  
Elisabeth Schwob ◽  
Yohannes Hagos ◽  
Gerhard Burckhardt ◽  
Birgitta C. Burckhardt
Keyword(s):  
Orphan Drug ◽  
Organic Anion ◽  
Xenopus Laevis Oocytes ◽  
Human Embryonic Kidney ◽  
Estrone Sulfate ◽  
Anion Transporters ◽  
293 Cells ◽  
Acetylglutamate Synthase ◽  
Inborn Defects ◽  
The Impact

Inborn defects in N-acetylglutamate (NAG) synthase (NAGS) cause a reduction of NAG, an essential cofactor for the initiation of the urea cycle. As a consequence, blood ammonium concentrations are elevated, leading to severe neurological disorders. The orphan drug N-carbamoylglutamate (NCG; Carbaglu), efficiently overcomes NAGS deficiency. However, not much is known about the transporters involved in the uptake, distribution, and elimination of the divalent organic anion NCG. Organic anion-transporting polypeptides (OATPs) as well as organic anion transporters (OATs) working in cooperation with sodium dicarboxylate cotransporter 3 (NaDC3) accept a wide variety of structurally unrelated drugs. To test for possible interactions with OATPs and OATs, the impact of NCG on these transporters in stably transfected human embryonic kidney-293 cells was measured. The two-electrode voltage-clamp technique was used to monitor NCG-mediated currents in Xenopus laevis oocytes that expressed NaDC3. Neither OATPs nor OAT2 and OAT3 interacted with NCG, but OAT1 transported NCG. In addition, NCG was identified as a high-affinity substrate of NaDC3. Preincubation of OAT4-transfected human embryonic kidney-293 cells with NCG showed an increased uptake of estrone sulfate, the reference substrate of OAT4, indicating efflux of NCG by OAT4. In summary, NaDC3 and, to a lesser extent, OAT1 are likely to be responsible for the uptake of NCG from the blood. Efflux of NCG across the luminal membrane into the tubular lumen probably occurs by OAT4 completing renal secretion of this drug.

Transport of cimetidine by flounder and human renal organic anion transporter 1

2003 ◽  
Vol 284 (3) ◽  
pp. F503-F509 ◽  
Author(s):  
Birgitta C. Burckhardt ◽  
Stefan Brai ◽  
Sönke Wallis ◽  
Wolfgang Krick ◽  
Natascha A. Wolff ◽  
...  
Keyword(s):  
Organic Anion ◽  
Human Kidney ◽  
Organic Anion Transporter ◽  
In Vivo Studies ◽  
Xenopus Laevis Oocytes ◽  
Organic Anion Transporters ◽  
Anion Transporters ◽  
Anion Transporter ◽  
Inward Currents

The H2-receptor antagonist cimetidine is efficiently excreted by the kidneys. In vivo studies indicated an interaction of cimetidine not only with transporters for basolateral uptake of organic cations but also with those involved in excretion of organic anions. We therefore tested cimetidine as a possible substrate of the organic anion transporters cloned from winter flounder (fROAT) and from human kidney (hOAT1). Uptake of [3H]cimetidine into fROAT-expressing Xenopus laevis oocytes exceeded uptake into control oocytes. At −60-mV clamp potential, 1 mM cimetidine induced an inward current, which was smaller than that elicited by 0.1 mM PAH. Cimetidine concentrations exceeding 0.1 mM decreased PAH-induced inward currents, indicating interaction with the same transporter. At pH 6.6, no current was seen with 0.1 mM cimetidine, whereas at pH 8.6 a current was readily detectable, suggesting preferential translocation of uncharged cimetidine by fROAT. Oocytes expressing hOAT1 also showed [3H]cimetidine uptake. These data reveal cimetidine as a substrate for fROAT/hOAT1 and suggest that organic anion transporters contribute to cimetidine excretion in proximal tubules.

Cl−-dependent upregulation of human organic anion transporters: different effects on transport kinetics between hOAT1 and hOAT3

2007 ◽  
Vol 293 (1) ◽  
pp. F391-F397 ◽  
Author(s):  
Harumasa Ueo ◽  
Hideyuki Motohashi ◽  
Toshiya Katsura ◽  
Ken-ichi Inui
Keyword(s):  
Organic Anion ◽  
Substrate Recognition ◽  
Chloride Ion ◽  
Transport Kinetics ◽  
Hek293 Cells ◽  
Organic Anion Transporters ◽  
Basolateral Membranes ◽  
Estrone Sulfate ◽  
Anion Transporters ◽  
Threefold Increase

Chloride ion has a stimulatory effect on the transport of organic anions across renal basolateral membranes. However, the exact mechanisms at molecular levels have been unclear as of yet. Human organic anion transporters hOAT1 and hOAT3 play important roles in renal basolateral membranes. In this study, the effects of Cl− on the activities of these transporters were evaluated by using HEK293 cells stably expressing hOAT1 or hOAT3 (HEK-hOAT1 or HEK-hOAT3). The uptake of p-[14C]aminohippurate by HEK-hOAT1 and [3H]estrone sulfate by HEK-hOAT3 was greater in the presence of Cl− than in the presence of SO42− or gluconate. Additionally, the uptake of various compounds by HEK-hOAT1 and HEK-hOAT3 was significantly higher in the Cl−-containing medium than the gluconate-containing medium, suggesting that the influences of Cl− are not dependent on substrate and that Cl− directly stimulates the functions of hOAT1 and hOAT3. The substitution of gluconate with Cl− did not change the Km value for the uptake of p-[14C]aminohippurate by HEK-hOAT1 but caused an approximately threefold increase in the maximal uptake rate (Vmax) value. On the other hand, replacement of gluconate with Cl− decreased the Km value for the uptake of [3H]estrone sulfate and cefotiam by HEK-hOAT3 to about one-third, while it did not change the Vmax value. In summary, Cl− upregulates the activities of both hOAT1 and hOAT3, but its effects on transport kinetics differ between these transporters. It was suggested that Cl− participates in the trans-location process for hOAT1, and the substrate recognition process for hOAT3.

Environmental contaminants modulate transport activity of zebrafish organic anion transporters Oat1 and Oat3

2020 ◽  
Vol 231 ◽  
pp. 108742
Author(s):  
Jelena Dragojević ◽  
Petra Marić ◽  
Jovica Lončar ◽  
Marta Popović ◽  
Ivan Mihaljević ◽  
...  
Keyword(s):  
Organic Anion ◽  
Environmental Contaminants ◽  
Organic Anion Transporters ◽  
Transport Activity ◽  
Anion Transporters

Interaction and transport of kynurenic acid via human organic anion transporters hOAT1 and hOAT3

2012 ◽  
Vol 65 (2) ◽  
pp. 254-260 ◽  
Author(s):  
Yuichi Uwai ◽  
Hiroaki Honjo ◽  
Kikuo Iwamoto
Keyword(s):  
Kynurenic Acid ◽  
Organic Anion ◽  
Organic Anion Transporters ◽  
Anion Transporters

Human organic anion transporter OAT1 is not responsible for glutathione transport but mediates transport of glutamate derivatives

2013 ◽  
Vol 304 (4) ◽  
pp. F403-F409 ◽  
Author(s):  
Yohannes Hagos ◽  
Gerhard Burckhardt ◽  
Birgitta C. Burckhardt
Keyword(s):  
Organic Anion ◽  
Organic Anion Transporter ◽  
Hek293 Cells ◽  
Toxic Substances ◽  
Organic Anion Transporters ◽  
Estrone Sulfate ◽  
Anion Transporters ◽  
Anion Transporter ◽  
Cellular Integrity ◽  
High Concentrations

Due to their clearance function, the kidneys are exposed to high concentrations of oxidants and potentially toxic substances. To maintain cellular integrity, renal cells have to be protected by sufficient concentrations of the antioxidant glutathione (GSH). We tested whether GSH or its precursors are taken up by human organic anion transporters 1 (OAT1) and 3 (OAT3) stably expressed in HEK293 cells. GSH did not inhibit uptake of p-aminohippurate (PAH) or of estrone sulfate (ES) in OAT3-transfected HEK293 cells. In OAT1-transfected cells, GSH reduced the uptake of PAH marginally. Among the GSH constituent amino acids, glutamate, cysteine, and glycine, only glutamate inhibited OAT1, but labeled glutamate was not taken up by a probenecid-inhibitable transport system. Thus OAT1 binds glutamate but is unable to translocate it. The GSH precursor dipeptide, cysteinyl glycine (cysgly), and the glutamate derivative N-acetyl glutamate (NAG), inhibited uptake of PAH when present in the medium and trans-stimulated uptake of PAH from the intracellular side, indicating that they are hitherto unrecognized transported substrates of OAT1. N-acetyl aspartate weakly interacted with OAT1, but aspartate did not. NAG inhibited also OAT3, albeit with much lower affinity compared with OAT1, and glutamate did not interact with OAT3 at all. Taken together, human OAT3 and OAT1 cannot be involved in renal GSH extraction from the blood. However, OAT1 could support intracellular GSH synthesis by taking up cysteinyl glycine.

Counter-flow suggests transport of dantrolene and 5-OH dantrolene by the organic anion transporters 2 (OAT2) and 3 (OAT3)

2016 ◽  
Vol 468 (11-12) ◽  
pp. 1909-1918 ◽  
Author(s):  
Birgitta C. Burckhardt ◽  
Maja Henjakovic ◽  
Yohannes Hagos ◽  
Gerhard Burckhardt
Keyword(s):  
Organic Anion ◽  
Organic Anion Transporters ◽  
Counter Flow ◽  
Anion Transporters

Integrated Approach of In Vivo and In Vitro Evaluation of the Involvement of Hepatic Uptake Organic Anion Transporters in the Drug Disposition in Rats Using Rifampicin as an Inhibitor

2013 ◽  
Vol 41 (7) ◽  
pp. 1442-1449 ◽  
Author(s):  
Tomoki Imaoka ◽  
Tsuyoshi Mikkaichi ◽  
Koji Abe ◽  
Masakazu Hirouchi ◽  
Noriko Okudaira ◽  
...  
Keyword(s):  
Drug Disposition ◽  
Organic Anion ◽  
Integrated Approach ◽  
Hepatic Uptake ◽  
Organic Anion Transporters ◽  
In Vitro Evaluation ◽  
Anion Transporters
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