scholarly journals Expression of the conjugate export pump encoded by the mrp2 gene in the apical membrane of kidney proximal tubules.

1997 ◽  
Vol 8 (8) ◽  
pp. 1213-1221 ◽  
Author(s):  
T P Schaub ◽  
J Kartenbeck ◽  
J König ◽  
O Vogel ◽  
R Witzgall ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Laser Scanning ◽  
Apical Membrane ◽  
Rat Kidney ◽  
Organic Anion ◽  
Laser Scanning Microscopy ◽  
Organic Anion Transporter ◽  
Confocal Laser ◽  
Membrane Domain ◽  
Anion Transporter

A novel ATP-dependent export pump for amphiphilic anionic conjugates, which has been cloned recently from liver, was identified in rat kidney and localized to the apical membrane domain of proximal tubule epithelia. This 190-kD membrane glycoprotein (Mrp2) has been described previously as the hepatocyte canalicular isoform of the multidrug resistance protein and as the canalicular multispecific organic anion transporter. Mrp2 was identified in kidney by reverse transcription PCR followed by sequencing of the amplified 786-bp fragment and by immunoblotting, using an antibody specifically reacting with the carboxy terminus of rat Mrp2. Double immunofluorescence and confocal laser-scanning microscopy showed the presence of Mrp2 in the brush-border membrane domain of segments S1, S2, and S3 of proximal tubule epithelia. Mrp2 was not detectable in other segments of the nephron. The onset of Mrp2 expression during development occurred in a very early stage of nephron development. Mrp2 represents the first cloned ATP-dependent export pump for amphiphilic organic anions identified in kidney and localized to the apical membrane domain of proximal tubule epithelia. Mrp2 may contribute to cellular detoxification and to the secretion of endogenous and xenobiotic anionic substances, most of which are conjugates, from the blood into urine.

Renal organic anion transporter 1 is maldistributed and diminishes in proximal tubule cells but increases in vasculature after ischemia and reperfusion

2008 ◽  
Vol 295 (6) ◽  
pp. F1807-F1816 ◽  
Author(s):  
Osun Kwon ◽  
Wei-Wei Wang ◽  
Shane Miller
Keyword(s):  
Proximal Tubule ◽  
Ischemia Reperfusion ◽  
Organic Anion ◽  
Basolateral Membrane ◽  
Kidney Injury ◽  
Organic Anion Transporter ◽  
Membrane Domain ◽  
Proximal Tubule Cells ◽  
Anion Transporter ◽  
Tubule Cells

Renal solute clearances are reduced in ischemic acute kidney injury. However, the mechanisms explaining how solute clearance is impaired have not been clarified. Recently, we reported that cadaveric renal allografts exhibit maldistribution of organic anion transporter 1 (OAT1) in proximal tubule cells after ischemia and reperfusion, resulting in impairment of PAH clearance. In the present study, we characterized renal OAT1 in detail after ischemia-reperfusion using a rat model. We analyzed renal OAT1 using confocal microscopy with a three-dimensional reconstruction of serial optical images, Western blot, and quantitative real-time RT-PCR. OAT1 was distributed to basolateral membranes of proximal tubule cells in controls. With ischemia, OAT1 decreased in basolateral membrane, especially in the lateral membrane domain, and appeared diffusely in cytoplasm. After reperfusion following 60-min ischemia, OAT1 often formed cytoplasmic aggregates. The staining for OAT1 started reappearing in lateral membrane domain 1 h after reperfusion. The basolateral membrane staining was relatively well discernable at 240 h of reperfusion. Of note, a distinct increase in OAT1 expression was noted in vasculature early after ischemia and after reperfusion. The total amount of OAT1 protein expression in the kidney diminished after ischemia-reperfusion in a duration-dependent manner until 72 h, when they began to recover. However, even at 240 h, the amount of OAT1 did not reach control levels. The kidney tissues tended to show a remarkable but transient increase in mRNA expression for OAT1 at 5 min of ischemia. Our findings may provide insights of renal OAT1 in its cellular localization and response during ischemic acute kidney injury and recovery from it.

scholarly journals Identification of a Novel Voltage-driven Organic Anion Transporter Present at Apical Membrane of Renal Proximal Tubule

2003 ◽  
Vol 278 (30) ◽  
pp. 27930-27938 ◽  
Author(s):  
Promsuk Jutabha ◽  
Yoshikatsu Kanai ◽  
Makoto Hosoyamada ◽  
Arthit Chairoungdua ◽  
Do Kyung Kim ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Apical Membrane ◽  
Organic Anion ◽  
Renal Proximal Tubule ◽  
Organic Anion Transporter ◽  
Anion Transporter

Identification of an apical \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{Cl}^{-}{/}\mathrm{HCO}_{3}^{-}\) \end{document} exchanger in rat kidney proximal tubule

2003 ◽  
Vol 285 (3) ◽  
pp. C608-C617 ◽  
Author(s):  
Snezana Petrovic ◽  
Liyun Ma ◽  
Zhaohui Wang ◽  
Manoocher Soleimani
Keyword(s):  
Proximal Tubule ◽  
Apical Membrane ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Immunocytochemical Staining ◽  
Kidney Cortex ◽  
Rat Kidney Cortex ◽  
Kidney Proximal Tubule ◽  
Anion Transporter

SLC26A6 (or putative anion transporter 1, PAT1) is located on the apical membrane of mouse kidney proximal tubule and mediates [Formula: see text] exchange in in vitro expression systems. We hypothesized that PAT1 along with a [Formula: see text] exchange is present in apical membranes of rat kidney proximal tubules. Northern hybridizations indicated the exclusive expression of SLC26A6 (PAT1 or CFEX) in rat kidney cortex, and immunocytochemical staining localized SLC26A6 on the apical membrane of proximal tubules, with complete prevention of the labeling with the preadsorbed serum. To examine the functional presence of apical [Formula: see text] exchanger, proximal tubules were isolated, microperfused, loaded with the pH-sensitive dye BCPCF-AM, and examined by digital ratiometric imaging. The pH of the perfusate and bath was kept at 7.4. Buffering capacity was measured, and transport rates were calculated as equivalent base flux. The results showed that in the presence of basolateral DIDS (to inhibit [Formula: see text] cotransporter 1) and apical EIPA (to inhibit Na+/H+ exchanger 3), the magnitude of cell acidification in response to addition of luminal Cl– was ∼5.0-fold higher in the presence than in the absence of [Formula: see text]. The Cl–-dependent base transport was inhibited by ∼61% in the presence of 0.5 mM luminal DIDS. The presence of physiological concentrations of oxalate in the lumen (200 μM) did not affect the [Formula: see text] exchange activity. These results are consistent with the presence of SLC26A6 (PAT1) and [Formula: see text] exchanger activity in the apical membrane of rat kidney proximal tubule. We propose that SLC26A6 is likely responsible for the apical [Formula: see text] (and Cl–/OH–) exchanger activities in kidney proximal tubule.

scholarly journals Sex Hormone Regulation of Rat Organic Anion Transporter 3 (rOAT3) Expression in Rat Kidney

2003 ◽  
Vol 49 (3) ◽  
pp. 233-238 ◽  
Author(s):  
Masanori Katakura ◽  
Naomi Kudo ◽  
Mari Okazaki ◽  
Yasuhide Hibino ◽  
Yoichi Kawashima
Keyword(s):  
Rat Kidney ◽  
Organic Anion ◽  
Sex Hormone ◽  
Organic Anion Transporter ◽  
Hormone Regulation ◽  
Anion Transporter ◽  
Organic Anion Transporter 3

Sodium-dependent methotrexate carrier-1 is expressed in rat kidney: cloning and functional characterization

2004 ◽  
Vol 286 (3) ◽  
pp. F564-F571 ◽  
Author(s):  
Carsten Kneuer ◽  
Kerstin U. Honscha ◽  
Walther Honscha
Keyword(s):  
Laser Scanning ◽  
Mdck Cells ◽  
Rat Kidney ◽  
Functional Characterization ◽  
Regulatory Elements ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Strong Inhibitor ◽  
Major Band ◽  
Sodium Dependent

Previous Northern blot studies suggested strong expression of a homolog to the sodium-dependent hepatocellular methotrexate transporter in the kidneys. Here, we report on the cloning of the cDNA for the renal methotrexate carrier isoform-1 (RK-MTX-1) and its functional characterization. Sequencing revealed 97% homology to the rat liver methotrexate carrier with an identical open reading frame. Differences were located in the 5′-untranslated region and resulted in the absence of putative regulatory elements (Barbie box, Ah/ARNT receptor) identified in the cDNA for the hepatocellular carrier. For functional characterization, MTX-1 cDNA was stably expressed in Madin-Darby canine kidney (MDCK) cells. A sodium-dependent transport of methotrexate with a Kmof 41 μM and a Vmaxof 337 pmol·mg protein-1·min-1was observed. This uptake was blocked by the reduced folates dihydro- and tetrahydrofolate as well as by methotrexate itself. Folate was inhibiting only weakly, whereas 5-methyltetrahydrofolate was a strong inhibitor. Further inhibitors of the methotrexate transport included the bile acids cholate and taurocholate and xenobiotics like bumetanide and BSP. PAH, ouabain, bumetanide, cholate, taurocholate, and acetyl salicylic acid were tested as potential substrates. However, none of these substances was transported by MTX-1. Furthermore, expression of RK-MTX-1 in MDCK cells enhanced methotrexate toxicity in these cells fivefold. Analysis of a fusion protein of RK-MTX-1 and the influenza virus hemagglutinin epitope by immunoblotting revealed a major band at 72 kDa within the cell membrane but not in the soluble fraction of transfected MDCK. Indirect immunofluorescence staining revealed an exclusive localization of the carrier in the plasma membrane, and by confocal laser-scanning microscopy we were able to demonstrate that the protein is expressed in the serosal region of MDCK tubules grown in a morphogenic collagen gel model.

scholarly journals cDNA cloning of rat kidney organic anion transporter family.

1996 ◽  
Vol 71 ◽  
pp. 291
Author(s):  
Takashi Sekine ◽  
Makoto Hosoyamada ◽  
Yoshikatsu Kanai ◽  
Hitoshi Endou
Keyword(s):  
Cdna Cloning ◽  
Rat Kidney ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Anion Transporter ◽  
Transporter Family

Renal expression of organic anion transporter OAT2 in rats and mice is regulated by sex hormones

2007 ◽  
Vol 292 (1) ◽  
pp. F361-F372 ◽  
Author(s):  
Marija Ljubojević ◽  
Daniela Balen ◽  
Davorka Breljak ◽  
Marija Kušan ◽  
Naohiko Anzai ◽  
...  
Keyword(s):  
Gender Differences ◽  
Mrna Expression ◽  
Rat Kidney ◽  
Organic Anion ◽  
Staining Intensity ◽  
Protein Band ◽  
Organic Anion Transporter ◽  
Adult Rats ◽  
Anion Transporters ◽  
Anion Transporter

The renal reabsorption and/or excretion of various organic anions is mediated by specific organic anion transporters (OATs). OAT2 (Slc22a7) has been identified in rat kidney, where its mRNA expression exhibits gender differences [females (F) > males (M)]. The exact localization of OAT2 protein in the mammalian kidney has not been reported. Here we studied the expression of OAT2 mRNA by RT-PCR and its protein by Western blotting (WB) and immunocytochemistry (IC) in kidneys of adult intact and gonadectomized M and F, sex hormone-treated castrated M, and prepubertal M and F rats, and the protein in adult M and F mice. In adult rats, the expression of OAT2 mRNA was predominant in the outer stripe (OS) tissue, exhibiting 1) gender dependency (F > M), 2) upregulation by castration and downregulation by ovariectomy, and 3) strong downregulation by testosterone and weak upregulation by estradiol and progesterone treatment. A polyclonal antibody against rat OAT2 on WB of isolated renal membranes labeled a ∼66-kDa protein band that was stronger in F. By IC, the antibody exclusively stained brush border (BB) of the proximal tubule S3 segment (S3) in the OS and medullary rays (F > M). In variously treated rats, the pattern of 66-kDa band density in the OS membranes and the staining intensity of BB in S3 matched the mRNA expression. The expression of OAT2 protein in prepubertal rats was low and gender independent. In mice, the expression pattern largely resembled that in rats. Therefore, OAT2 in rat (and mouse) kidney is localized to the BB of S3, exhibiting gender differences (F > M) that appear in puberty and are caused by strong androgen inhibition and weak estrogen and progesterone stimulation.

scholarly journals Cyclic AMP stimulates sorting of the canalicular organic anion transporter (Mrp2/cMoat) to the apical domain in hepatocyte couplets

1998 ◽  
Vol 111 (8) ◽  
pp. 1137-1145 ◽  
Author(s):  
H. Roelofsen ◽  
C.J. Soroka ◽  
D. Keppler ◽  
J.L. Boyer
Keyword(s):  
Apical Membrane ◽  
Organic Anion ◽  
Anion Transport ◽  
Transport Protein ◽  
Organic Anion Transporter ◽  
Multidrug Resistance Protein ◽  
Multidrug Resistance Protein 2 ◽  
Apical Domain ◽  
Anion Transporter ◽  
Resistance Protein

The canalicular membrane of rat hepatocytes contains an ATP-dependent multispecific organic anion transporter, also named multidrug resistance protein 2, that is responsible for the biliary secretion of several amphiphilic organic anions. This transport function is markedly diminished in mutant rats that lack the transport protein. To assess the role of vesicle traffic in the regulation of canalicular organic anion transport, we have examined the redistribution of the transporter to the canalicular membrane and the effect of cAMP on this process in isolated hepatocyte couplets, which retain secretory polarity. The partial disruption of cell-cell contact, due to the isolation procedure, leaves the couplet with both remnant apical membranes, as a source of apical proteins, and an intact apical domain and lumen, to which these proteins are targeted. The changes in distribution of the transporter were correlated to the apical excretion of a fluorescent substrate, glutathione-methylfluorescein. The data obtained in this study show that the transport protein, endocytosed from apical membrane remnants, first is redistributed along the basolateral plasma membrane. Then it is transcytosed to the remaining apical pole in a microtubule-dependent fashion, followed by the fusion of transporter-containing vesicles with the apical membrane. The cAMP analog dibutyrylcAMP stimulates all three steps, resulting in increased apically located transport protein, glutathione-methylfluorescein transport activity and apical membrane circumference. These findings indicate that the organic anion transport capacity of the apical membrane in hepatocyte couplets is regulated by cAMP-stimulated sorting of the multidrug resistance protein 2 to the apical membrane. The relevance of this phenomenon for the intact liver is discussed.

scholarly journals Peritubular transport of ochratoxin A by single rabbit renal proximal tubules.

1998 ◽  
Vol 9 (11) ◽  
pp. 1973-1982 ◽  
Author(s):  
J R Welborn ◽  
C E Groves ◽  
S H Wright
Keyword(s):  
Proximal Tubule ◽  
Ochratoxin A ◽  
Organic Anion ◽  
High Capacity ◽  
Organic Anion Transporter ◽  
Epifluorescence Microscopy ◽  
Proximal Tubule Cells ◽  
Anion Transporter ◽  
Uptake Medium ◽  
Proximal Tubule Segments

Epifluorescence microscopy was used to study peritubular transport of the fluorescent mycotoxin ochratoxin A (OTA) into single proximal tubule segments of the rabbit. Initial rates of OTA uptake into S2 segments were saturable and adequately described by Michaelis-Menten kinetics, with an apparent Km of 2.2+/-0.3 microM (SEM). Several lines of evidence indicated that peritubular uptake of OTA in S2 segments was effectively limited to the "classical" organic anion transporter. First, 5 mM p-aminohippurate (PAH) cis-inhibited the uptake of 1 microM OTA into tubules by 96%. Kinetic analysis of the inhibition of OTA uptake by PAH (100 microM to 5 mM) yielded an apparent Ki of 164 microM, similar to the 100 to 200 microM range of Km values previously reported for the peritubular uptake of PAH. Second, efflux of OTA from tubules was trans-stimulated 3.2-fold by the presence of 2.5 mM PAH in the uptake medium. Third, 100 microM alpha-ketoglutarate (alphaKG) trans-stimulated the uptake rate of 1 microM OTA by 1.8-fold. Fourth, besides PAH, other organic anions effectively cis-inhibited the uptake of 1 microM OTA into tubules (inhibitor, % inhibition): 1.5 mM alphaKG, 80%; 1 mM probenecid, 100%; 1 mM piroxicam, 100%; 1 mM octanoate, 100%. In contrast, 1.5 mM tetraethylammonium, an organic cation, blocked uptake of 1 microM OTA by only 7%. The inhibition of OTA uptake into S1 and S3 segments of the proximal tubule was qualitatively similar: 5 mM PAH cis-inhibited the uptake of 1 microM OTA by approximately 95% in both S1 and S3 segments. Thus, peritubular OTA uptake into all segments of the proximal tubule appears to be dominated by its interaction with the classical organic anion transporter. The high-affinity and relatively high capacity of this pathway for OTA suggest that peritubular uptake may be a significant avenue for the entry of this toxin into proximal tubule cells.

scholarly journals Remote sensing and signaling in kidney proximal tubules stimulates gut microbiome-derived organic anion secretion

2019 ◽  
Vol 116 (32) ◽  
pp. 16105-16110 ◽  
Author(s):  
Jitske Jansen ◽  
Katja Jansen ◽  
Ellen Neven ◽  
Ruben Poesen ◽  
Amr Othman ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Gut Microbiome ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Indoxyl Sulfate ◽  
Regulation Mechanism ◽  
Uremic Toxin ◽  
Proximal Tubule Cell ◽  
Anion Secretion ◽  
Anion Transporter

Membrane transporters and receptors are responsible for balancing nutrient and metabolite levels to aid body homeostasis. Here, we report that proximal tubule cells in kidneys sense elevated endogenous, gut microbiome-derived, metabolite levels through EGF receptors and downstream signaling to induce their secretion by up-regulating the organic anion transporter-1 (OAT1). Remote metabolite sensing and signaling was observed in kidneys from healthy volunteers and rats in vivo, leading to induced OAT1 expression and increased removal of indoxyl sulfate, a prototypical microbiome-derived metabolite and uremic toxin. Using 2D and 3D human proximal tubule cell models, we show that indoxyl sulfate induces OAT1 via AhR and EGFR signaling, controlled by miR-223. Concomitantly produced reactive oxygen species (ROS) control OAT1 activity and are balanced by the glutathione pathway, as confirmed by cellular metabolomic profiling. Collectively, we demonstrate remote metabolite sensing and signaling as an effective OAT1 regulation mechanism to maintain plasma metabolite levels by controlling their secretion.

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