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.

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 Expression of Organic Anion Transporter 1 or 3 in Human Kidney Proximal Tubule Cells Reduces Cisplatin Sensitivity

2018 ◽  
Vol 46 (5) ◽  
pp. 592-599 ◽  
Author(s):  
Tom T. G. Nieskens ◽  
Janny G. P. Peters ◽  
Dina Dabaghie ◽  
Daphne Korte ◽  
Katja Jansen ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Organic Anion ◽  
Human Kidney ◽  
Organic Anion Transporter ◽  
Proximal Tubule Cells ◽  
Kidney Proximal Tubule ◽  
Anion Transporter ◽  
Cisplatin Sensitivity ◽  
Tubule Cells

Inhibition of initial transport rate of basolateral organic anion carrier in renal PT by BK and phenylephrine

1999 ◽  
Vol 277 (2) ◽  
pp. F251-F256 ◽  
Author(s):  
Michael Gekle ◽  
Sigrid Mildenberger ◽  
Christoph Sauvant ◽  
Dallas Bednarczyk ◽  
Stephen H. Wright ◽  
...  
Keyword(s):  
Direct Action ◽  
Organic Anion ◽  
Specific Inhibitor ◽  
Peptide Hormone ◽  
Organic Anion Transporter ◽  
Epifluorescence Microscopy ◽  
Anion Transporter ◽  
Initial Uptake Rate ◽  
Continuous Presence

The effect of ligands for phospholipase C-coupled receptors and of protein kinase C (PKC) stimulation with phorbol ester [phorbol 12-myristate 13-acetate (PMA)] or 1,2-dioctanoyl- sn-glycerol on the activity of the basolateral organic anion transporter (OAT) in S2 segments of single, nonperfused rabbit proximal tubules (PT) was measured with the use of fluorescein and epifluorescence microscopy. The initial uptake rate (25 s, OAT activity) was measured in real time by using conditions similar to those found in vivo. Stimulation of PKC with PMA or 1,2-dioctanoyl- sn-glycerol led to an inhibition of OAT activity, which could be prevented by 10−7 mol/l of the PKC-specific inhibitor bisindolylmaleimide. The α1-receptor agonist phenylephrine as well as the peptide hormone bradykinin induced a reversible decrease of OAT activity, which was prevented by bisindolylmaleimide. The observed effect was not due to a decrease in the concentration of the counterion α-ketoglutarate or to impaired α-ketoglutarate recycling, because it was unchanged in the continuous presence of α-ketoglutarate or methyl succinate. We conclude that physiological stimuli can inhibit the activity of OAT in rabbit PT via PKC. The effect is not mediated by alterations in counterion availability but by a direct action on the OAT.

scholarly journals Role of human organic anion transporter 4 in the transport of ochratoxin A

2002 ◽  
Vol 1590 (1-3) ◽  
pp. 64-75 ◽  
Author(s):  
Ellappan Babu ◽  
Michio Takeda ◽  
Shinichi Narikawa ◽  
Yukari Kobayashi ◽  
Atsushi Enomoto ◽  
...  
Keyword(s):  
Ochratoxin A ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Anion Transporter

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.

Liver X receptor activation downregulates organic anion transporter 1 (OAT1) in the renal proximal tubule

2012 ◽  
Vol 302 (5) ◽  
pp. F552-F560 ◽  
Author(s):  
Suticha Kittayaruksakul ◽  
Sunhapas Soodvilai ◽  
Nithi Asavapanumas ◽  
Chatchai Muanprasat ◽  
Varanuj Chatsudthipong
Keyword(s):  
Proximal Tubule ◽  
Organic Anion ◽  
Basolateral Membrane ◽  
Receptor Activation ◽  
Inhibitory Effect ◽  
Renal Proximal Tubule ◽  
Organic Anion Transporter ◽  
Anion Transporter ◽  
X Receptors ◽  
Lxr Agonists

Liver X receptors (LXRs) play an important role in the regulation of cholesterol by regulating several transporters. In this study, we investigated the role of LXRs in the regulation of human organic anion transporter 1 (hOAT1), a major transporter localized in the basolateral membrane of the renal proximal tubule. Exposure of renal S2 cells expressing hOAT1 to LXR agonists (TO901317 and GW3965) and their endogenous ligand [22(R)-hydroxycholesterol] led to the inhibition of hOAT1-mediated [14C]PAH uptake. This inhibition was abolished by coincubation of the above agonists with 22(S)-hydroxycholesterol, an LXR antagonist. Moreover, it was found that the effect of LXR agonists was not mediated by changes in intracellular cholesterol levels. Interestingly, the inhibitory effect of LXRs was enhanced in the presence of 9- cis retinoic acid, a retinoic X receptor agonist. Kinetic analysis revealed that LXR activation decreased the maximum rate of PAH transport ( Jmax) but had no effect on the affinity of the transporter ( Kt). This result correlated well with data from Western blot analysis, which showed the decrease in hOAT1 expression following LXR activation. Similarly, TO901317 inhibited [14C]PAH uptake by the renal cortical slices as well as decreasing mOAT1 protein expression in mouse kidney. Our findings indicated for the first time that hOAT1 was downregulated by LXR activation in the renal proximal tubule.

Identification and functional assessment of the novel murine organic anion transporter Oat5 (Slc22a19) expressed in kidney

2004 ◽  
Vol 287 (2) ◽  
pp. F236-F244 ◽  
Author(s):  
Geri L. Youngblood ◽  
Douglas H. Sweet
Keyword(s):  
Ochratoxin A ◽  
Cdna Clone ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Xenopus Laevis Oocytes ◽  
Hepatic Expression ◽  
Estrone Sulfate ◽  
Anion Transporter ◽  
Transporter Family ◽  
2,4 Dichlorophenoxyacetic Acid

An uncharacterized murine cDNA clone was identified and, through sequence, phylogenetic, and functional analysis, determined to encode the newest member of the organic anion transporter family, organic anion transporter 5 (Oat5; Slc22a19). The Oat5 cDNA clone contained an insert 1,964 bp in length with a predicted open reading frame (from bp 84 to bp 1,739) coding for a peptide 551 amino acids long. Slc22a19 was localized to mouse chromosome 19 near the genes encoding Oat1 ( Slc22a6) and Oat3 ( Slc22a8). Northern blot analysis revealed Oat5 is highly expressed in the kidney of adult mice and rats. No sexual dimorphism in renal or hepatic expression of Oat5 was observed. Unlike Oat1–3, Oat5 expression was not detected in the choroid plexus of either mice or rats. Murine Oat5-expressing Xenopus laevis oocytes supported increased accumulation of the mycotoxin ochratoxin A, compared with water-injected control oocytes. This uptake was significantly inhibited by probenecid and the organic anions 2,4-dichlorophenoxyacetic acid, salicylate, and estrone sulfate but not by para-aminohippurate or urate. Transport of ochratoxin A by murine Oat5 was saturable, with an estimated Km of 2.0 ± 0.45 μM. Oat5-mediated transport was neither cis-inhibited nor trans-stimulated by the dicarboxylate glutarate. Uptake was also completely unaffected by short-circuiting of the membrane potential. Thus the motive forces behind Oat5 function, which provide insight into its membrane localization, need to be further resolved. These data demonstrate for the first time that this newly identified gene encodes a protein that functions as an organic anion transporter.

Organic anion transporter 3 (Slc22a8) is a dicarboxylate exchanger indirectly coupled to the Na+gradient

2003 ◽  
Vol 284 (4) ◽  
pp. F763-F769 ◽  
Author(s):  
Douglas H. Sweet ◽  
Lauretta M. S. Chan ◽  
Ramsey Walden ◽  
Xiao-Ping Yang ◽  
David S. Miller ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Organic Anion ◽  
Renal Proximal Tubule ◽  
Organic Anion Transporter ◽  
Xenopus Laevis Oocytes ◽  
Estrone Sulfate ◽  
Anion Transporter ◽  
Renal Proximal Tubule Cells ◽  
Rat Renal Cortical Slices ◽  
Cortical Slices

Basolateral uptake of organic anions in renal proximal tubule cells is indirectly coupled to the Na+ gradient through Na+-dicarboxylate cotransport and organic anion/dicarboxylate exchange. One member of the organic anion transporter (OAT) family, Oat1, is expressed in the proximal tubule and is an organic anion/dicarboxylate exchanger. However, a second organic anion carrier, Oat3, is also highly expressed in the renal proximal tubule, but its mechanism is unclear. Thus we have assessed Oat3 function in Xenopus laevis oocytes and rat renal cortical slices. Probenecid-sensitive uptake of p-aminohippurate (PAH, an Oat1 and Oat3 substrate) and estrone sulfate (ES, an Oat3 substrate) in rat Oat3-expressing oocytes was significantly trans-stimulated by preloading the oocytes with the dicarboxylate glutarate (GA). GA stimulation of ES transport by oocytes coexpressing rabbit Na+-dicarboxylate cotransporter 1 and rat Oat3 was significantly inhibited when the preloading medium contained Li+ or methylsuccinate (MS) or when Na+ was absent. All these treatments inhibit the Na+-dicarboxylate cotransporter, but not rat Oat3. Li+, MS, and Na+ removal had no effect when applied during the ES uptake step, rather than during the GA preloading step. Concentrative ES uptake in rat renal cortical slices was also demonstrated to be probenecid and Na+ sensitive. Accumulation of ES was stimulated by GA, and this stimulation was completely blocked by probenecid, Li+, MS, taurocholate, and removal of Na+. Thus Oat3 functions as an organic anion/dicarboxylate exchanger that couples organic anion uptake indirectly to the Na+ gradient.

scholarly journals Ochratoxin A Secretion in Primary Cultures of Rabbit Renal Proximal Tubule Cells

1999 ◽  
Vol 10 (1) ◽  
pp. 13-20
Author(s):  
CARLOTTA E. GROVES ◽  
GRAZYNA NOWAK ◽  
MARK MORALES
Keyword(s):  
Proximal Tubule ◽  
Kinetic Analysis ◽  
Ochratoxin A ◽  
Organic Anion ◽  
Primary Cultures ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cells ◽  
High Affinity ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells

Abstract. Primary cultures of rabbit renal proximal tubule cells grown under improved culture conditions were used to study the transepithelial transport of the nephrotoxic mycotoxin ochratoxin A. The basal-to-apical transepithelial flux, i.e., secretion, of this fluorescence organic acid was measured in primary cultures of rabbit renal proximal tubule cells. The basal-to-apical flux of ochratoxin A increased with time and reached a steady state after 12 h. On the other hand, the apical-to-basal flux, i.e., reabsorption, of ochratoxin A was minimal over time. The secretory flux of ochratoxin A was as much as eightfold greater than the reabsorptive flux, indicating that net secretion is the primary mechanism for ochratoxin A clearance by the proximal tubule. The kinetic analysis of ochratoxin A flux revealed secretion to be a saturable and very high-affinity process with an apparent K50 of 0.33 ± 0.21 mM. A saturating concentration of the prototypical organic anion substrate para-aminohippurate (PAH) reduced ochratoxin A secretion by approximately 75%. The kinetic analysis of PAH inhibition of ochratoxin A secretion revealed an IC50 of 195 mM, which is similar to the IC50 for PAH inhibition of peritubular ochratoxin A uptake in tubule suspensions and the Km values for peritubular PAH uptake. The organic anions probenecid, octanoate, and α-ketoglutarate reduced ochratoxin A excretion to the same degree as PAH, whereas the amino acid phenylalanine had a minimal effect on ochratoxin A secretion. Thus, collectively, these observations indicate that the secretion of ochratoxin A in primary cultures of rabbit renal proximal tubules is limited to the organic anion secretory pathway. The high affinity measured for the basal-to-apical flux of ochratoxin A suggests that at concentrations typical of naturally occurring exposures, transepithelial secretion by the organic anion transport pathway represents a significant avenue for excretion of this mycotoxin by the renal proximal tubule.

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