Renal human organic anion transporter 3 increases the susceptibility of lymphoma cells to bendamustine uptake

2015 ◽  
Vol 308 (4) ◽  
pp. F330-F338 ◽  
Author(s):  
Yohannes Hagos ◽  
Philip Hundertmark ◽  
Volodymyr Shnitsar ◽  
Venkata V. V. R. Marada ◽  
Gerald Wulf ◽  
...  
Keyword(s):  
Organic Anion ◽  
Inhibitory Effect ◽  
Organic Anion Transporter ◽  
Lymphoma Cells ◽  
Estrone Sulfate ◽  
Anion Transporters ◽  
Lymphatic Leukemia ◽  
Anion Transporter ◽  
Nephritic Syndrome ◽  
The Impact

Chronic lymphatic leukemia (CLL) is often associated with nephritic syndrome. Effective treatment of CLL by chlorambucil and bendamustine leads to the restoration of renal function. In this contribution, we sought to elucidate the impact of organic anion transporters (OATs) on the uptake of bendamustine and chlorambucil as a probable reason for the superior efficacy of bendamustine over chlorambucil in the treatment of CLL. We examined the effects of structural analogs of p-aminohippurate (PAH), melphalan, chlorambucil, and bendamustine, on OAT1-mediated [3H]PAH uptake and OAT3- and OAT4-mediated [3H]estrone sulfate (ES) uptake in stably transfected human embryonic kidney-293 cells. Melphalan had no significant inhibitory effect on any OAT, whereas chlorambucil reduced OAT1-, OAT3-, and OAT4-mediated uptake of PAH or ES down to 14.6%, 16.3%, and 66.0% of control, respectively. Bendamustine inhibited only OAT3-mediated ES uptake, which was reduced down to 14.3% of control cells, suggesting that it interacts exclusively with OAT3. The IC50 value for OAT3 was calculated to be 0.8 μM. Real-time PCR experiments demonstrated a high expression of OAT3 in lymphoma cell lines as well as primary CLL cells. OAT3-mediated accumulation of bendamustine was associated with reduced cell proliferation and an increased rate of apoptosis. We conclude that the high efficacy of bendamustine in treating CLL might be partly contributed to the expression of OAT3 in lymphoma cells and the high affinity of bendamustine for this transporter.

Impact of Organic Anion Transporter 3 (OAT3) on Bendamustine Uptake of Lymphoma Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 4184-4184
Author(s):  
Yohannes Hagos ◽  
Gerald G. Wulf ◽  
Vladimir Shnitsar ◽  
Philip Hundertmark ◽  
Shvangi Gupta ◽  
...  
Keyword(s):  
Cell Lines ◽  
Organic Anion ◽  
Inhibitory Effect ◽  
Lymphoma Cell ◽  
Organic Anion Transporter ◽  
Hek293 Cells ◽  
Sulfate Uptake ◽  
Lymphoma Cells ◽  
Estrone Sulfate ◽  
Anion Transporter

Abstract One main problem of tumor therapy is the resistance of malignant cells to cytostatics due to high expression of efflux transporters. Whereas the role of these efflux transporters for tumor cell resistance is well established, little is known about uptake transporters, which may increase the sensibility of tumor cells for cytostatics. In the present study we addressed the interaction of cytostatics established for the treatment of lymphoma, namely melphalan, chlorambucil or bendamustine with human Organic Anion Transporter (OATs), which belong to the Solute carrier (SLC) gene family. We selected these cytostatics, because they show structural similarity to p-aminohyppurate (PAH), the model substrate of OATs. OATs are mainly expressed in the kidney, where they are responsible for the excretion of endogenous and exogenous organic anions like urate or various drugs e.g. diuretics. Initially, we examined the cis-inhibitory effect of melphalan, chlorambucil and bendamustine on OAT1-mediated [3H]PAH uptake as well as OAT3- and OAT4- mediated [3H]estrone sulfate uptake in HEK293 cells, which were stably transfected with these transporters. Melphalan did not show any significant inhibitory effect on all tested OATs. 100 μM chlorambucil reduced OAT1-, OAT3- and OAT4-mediated uptake of PAH or estrone sulfate down to 14.6 ± 0.17%, 16.3 ± 4.0% and 66.0 ± 1.4%, respectively. 100 μM bendamustine inhibited only OAT3-mediated estrone sulfate uptake up to 91.9 ± 0.5% compared to control cells. OAT1- or OAT4- facilitated transport of PAH and estrone sulfate remained unchanged by bendamustine, suggesting that bendamustine interacts exclusively with OAT3. To determine the affinity of OAT3 for bendamustine and chlorambucil, we performed concentration dependent inhibition of OAT3-mediated estrone sulfate uptake and calculated the Ki values for both cytostatics. Dixon-Plot evaluation confirmed a competitive inhibition of OAT3 by bendamustine as well as chlorambucil. The results demonstrated higher affinity of OAT3 for bendamustine with a Ki value of 2.7 μM than for chlorambucil, showing a Ki value of 38.2 μM. To elucidate the expression of OATs in lymphoma cell lines, we performed RT-PCR experiments. Our data demonstrate high expression of OAT3 in all cell lines compared to lymphocytes isolated from a normal person. No expression of OAT1 and OAT4 was observed any lymphoma cell lines. The expression of OAT3 in B-cell lymphoma cell lines Karpas, Raji, SudHL4 and T-cell lymphoma cell lines L428, Jurkat and Hut78 was quantified by real time PCR. The highest expression of OAT3 was observed in the order Jurkat>Hut78>SudHL4>L428>Raji>Karpas. The expression of OAT3 was confirmed by real time PCR in four patients with chronic lymphocytic leukamia. OAT3- dependent cytostatic effects of bendamustine was examined by [3H] thymidine incorporation. 30 min incubation of OAT3-expressing HEK293 cells with 10, 50 or 100 μM bendamustine significantly reduced the proliferation of transfected versus non-transfected cells. We conclude that the molecular background for the cytostatic efficiency of bendamustine in lymphoma cells is due to 1) the expression of OAT3 in lymphoma cells and 2) a the high affinity of OAT3 for bendamustine.

scholarly journals Interaction of Anticancer Drugs with Human Organic Anion Transporter hOAT4

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Chenchang Liu ◽  
Jinghui Zhang ◽  
Guofeng You
Keyword(s):  
Drug Interaction ◽  
Anticancer Drugs ◽  
Organic Anion ◽  
Inhibitory Effect ◽  
Organic Anion Transporter ◽  
Estrone Sulfate ◽  
Anion Transporters ◽  
Anion Transporter ◽  
Drug Drug Interaction ◽  
The Individual

Human organic anion transporter 4 (hOAT4) belongs to a family of multispecific organic anion transporters that play critical roles in the disposition of numerous drugs and therefore are the major sites for drug-drug interaction. Drug-drug interactions contribute significantly to the individual variation in drug response. hOAT4 is expressed in the kidney and placenta. In the current study, we examined the interaction of 36 anticancer drugs with hOAT4 in kidney COS-7 cells and placenta BeWo cells. Among the drugs tested, only epirubicin hydrochloride and dabrafenib mesylate exhibited > 50% cis-inhibitory effect, in COS-7 cells, on hOAT4-mediated uptake of estrone sulfate, a prototypical substrate for the transporter. The IC50values for epirubicin hydrochloride and dabrafenib mesylate were 5.24±0.95μM and 8.30±3.30μM, respectively. Dixon plot analysis revealed that inhibition by epirubicin hydrochloride was noncompetitive with aKi= 3μM whereas inhibition by dabrafenib mesylate was competitive with aKi= 4.26μM. Our results established that epirubicin hydrochloride and dabrafenib mesylate are inhibitors of hOAT4. Furthermore, by comparing our data with clinically relevant exposures of these drugs, we conclude that although the tendency for dabrafenib mesylate to cause drug-drug interaction through hOAT4 is insignificant in the kidney, the propensity for epirubicin hydrochloride to cause drug-drug interaction is high.

scholarly journals Organic Anion Transporter 1B1: An Important Factor in Hepatic Thyroid Hormone and Estrogen Transport and Metabolism

Endocrinology ◽  
2008 ◽  
Vol 149 (9) ◽  
pp. 4695-4701 ◽  
Author(s):  
Wendy M. van der Deure ◽  
Edith C. H. Friesema ◽  
Frank Jan de Jong ◽  
Yolanda B. de Rijke ◽  
Frank H. de Jong ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Hepatic Transport ◽  
Transfected Cells ◽  
Estrone Sulfate ◽  
Anion Transporters ◽  
Anion Transporter ◽  
Metabolism Of Bilirubin

Sulfation is an important pathway in the metabolism of thyroid hormone and estrogens. Sulfation of estrogens is reversible by estrogen sulfatase, but sulfation of thyroid hormone accelerates its degradation by the type 1 deiodinase in liver. Organic anion transporters (OATPs) are capable of transporting iodothyronine sulfates such as T4 sulfate (T4S), T3S, and rT3S or estrogen sulfates like estrone sulfate (E1S), but the major hepatic transporter for these conjugates has not been identified. A possible candidate is OATP1B1 because model substrates for this transporter include the bilirubin mimic bromosulfophthalein (BSP) and E1S, and it is highly and specifically expressed in liver. Therefore, OATP1B1-transfected COS1 cells were studied by analysis of BSP, E1S, and iodothyronine sulfate uptake and metabolism. Two Caucasian populations (155 blood donors and 1012 participants of the Rotterdam Scan Study) were genotyped for the OATP1B1-Val174Ala polymorphism and associated with bilirubin, E1S, and T4S levels. OATP1B1-transfected cells strongly induced uptake of BSP, E1S, T4S, T3S, and rT3S compared with mock-transfected cells. Metabolism of iodothyronine sulfates by cotransfected type 1 deiodinase was greatly augmented in the presence of OATP1B1. OATP1B1-Val174 showed a 40% higher induction of transport and metabolism of these substrates than OATP1B1-Ala174. Carriers of the OATP1B1-Ala174 allele had higher serum bilirubin, E1S, and T4S levels. In conclusion, OATP1B1 is an important factor in hepatic transport and metabolism of bilirubin, E1S, and iodothyronine sulfates. OATP1B1-Ala174 displays decreased transport activity and thereby gives rise to higher bilirubin, E1S, and T4S levels in carriers of this polymorphism.

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.

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.

scholarly journals Renal secretion of hydrochlorothiazide involves organic anion transporter 1/3, organic cation transporter 2, and multidrug and toxin extrusion protein 2-K

2019 ◽  
Vol 317 (4) ◽  
pp. F805-F814
Author(s):  
Jia Yin ◽  
David J. Wagner ◽  
Bhagwat Prasad ◽  
Nina Isoherranen ◽  
Kenneth E. Thummel ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Organic Cation ◽  
Organic Anion ◽  
Organic Cation Transporter ◽  
Tubular Secretion ◽  
Organic Anion Transporter ◽  
Anion Transporters ◽  
Anion Transporter ◽  
Organic Cation Transporter 2 ◽  
Toxin Extrusion

Hydrochlorothiazide (HCTZ) is the most widely used thiazide diuretic for the treatment of hypertension either alone or in combination with other antihypertensives. HCTZ is mainly cleared by the kidney via tubular secretion, but the underlying molecular mechanisms are unclear. Using cells stably expressing major renal organic anion and cation transporters [human organic anion transporter 1 (hOAT1), human organic anion transporter 3 (hOAT3), human organic cation transporter 2 (hOCT2), human multidrug and toxin extrusion 1 (hMATE1), and human multidrug and toxin extrusion 2-K (hMATE2-K)], we found that HCTZ interacted with both organic cation and anion transporters. Uptake experiments further showed that HCTZ is transported by hOAT1, hOAT3, hOCT2, and hMATE2-K but not by hMATE1. Detailed kinetic analysis coupled with quantification of membrane transporter proteins by targeted proteomics revealed that HCTZ is an excellent substrate for hOAT1 and hOAT3. The apparent affinities ( Km) for hOAT1 and hOAT3 were 112 ± 8 and 134 ± 13 μM, respectively, and the calculated turnover numbers ( kcat) were 2.48 and 0.79 s−1, respectively. On the other hand, hOCT2 and hMATE2-K showed much lower affinity for HCTZ. The calculated transport efficiency ( kcat/ Km) at the single transporter level followed the rank order of hOAT1> hOAT3 > hOCT2 and hMATE2-K, suggesting a major role of organic anion transporters in tubular secretion of HCTZ. In vitro inhibition experiments further suggested that HCTZ is not a clinically relevant inhibitor for hOAT1 or hOAT3. However, strong in vivo inhibitors of hOAT1/3 may alter renal secretion of HCTZ. Together, our study elucidated the molecular mechanisms underlying renal handling of HCTZ and revealed potential pathways involved in the disposition and drug-drug interactions for this important antihypertensive drug in the kidney.

scholarly journals Human organic anion transporter 2 is distinct from organic anion transporters 1 and 3 with respect to transport function

2015 ◽  
Vol 309 (10) ◽  
pp. F843-F851 ◽  
Author(s):  
Maja Henjakovic ◽  
Yohannes Hagos ◽  
Wolfgang Krick ◽  
Gerhard Burckhardt ◽  
Birgitta C. Burckhardt
Keyword(s):  
Organic Anion ◽  
Organic Anion Transporter ◽  
Substrate Uptake ◽  
Organic Anion Transporters ◽  
Counter Anion ◽  
Anion Transporters ◽  
Anion Transporter ◽  
293 Cells ◽  
High K ◽  
Resistance Protein

Phylogentically, organic anion transporter (OAT)1 and OAT3 are closely related, whereas OAT2 is more distant. Experiments with human embryonic kidney-293 cells stably transfected with human OAT1, OAT2, or OAT3 were performed to compare selected transport properties. Common to OAT1, OAT2, and OAT3 is their ability to transport cGMP. OAT2 interacted with prostaglandins, and cGMP uptake was inhibited by PGE2 and PGF2α with IC50 values of 40.8 and 12.7 μM, respectively. OAT1 (IC50: 23.7 μM), OAT2 (IC50: 9.5 μM), and OAT3 (IC50: 1.6 μM) were potently inhibited by MK571, an established multidrug resistance protein inhibitor. OAT2-mediated cGMP uptake was not inhibited by short-chain monocarboxylates and, as opposed to OAT1 and OAT3, not by dicarboxylates. Consequently, OAT2 showed no cGMP/glutarate exchange. OAT1 and OAT3 exhibited a pH and a Cl− dependence with higher substrate uptake at acidic pH and lower substrate uptake in the absence of Cl−, respectively. Such pH and Cl− dependencies were not observed with OAT2. Depolarization of membrane potential by high K+ concentrations in the presence of the K+ ionophore valinomycin left cGMP uptake unaffected. In addition to cGMP, OAT2 transported urate and glutamate, but cGMP/glutamate exchange could not be demonstrated. These experiments suggest that OAT2-mediated cGMP uptake does not occur via exchange with monocarboxylates, dicarboxylates, and hydroxyl ions. The counter anion for electroneutral cGMP uptake remains to be identified.

Hypouricemic Effects ofArmillaria melleaon Hyperuricemic Mice Regulated through OAT1 and CNT2

2018 ◽  
Vol 46 (03) ◽  
pp. 585-599 ◽  
Author(s):  
Tianqiao Yong ◽  
Shaodan Chen ◽  
Yizhen Xie ◽  
Diling Chen ◽  
Jiyan Su ◽  
...  
Keyword(s):  
Gastrointestinal Tract ◽  
Glucose Transporter ◽  
Organic Anion ◽  
Inhibitory Effect ◽  
Organic Anion Transporter ◽  
Nucleoside Transporter ◽  
Inhibitory Effects ◽  
Concentrative Nucleoside Transporter ◽  
Anion Transporter ◽  
Glucose Transporter 9

Ethanol and water extracts of Armillaria mellea were prepared by directly soaking A. mellea in ethanol (AME) at 65[Formula: see text]C, followed by decocting the remains in water (AMW) at 85[Formula: see text]C. Significantly, AME and AMW at 30, 60 and 120[Formula: see text]mg/kg exhibited excellent hypouricemic actions, causing remarkable declines from hyperuricemic control (351[Formula: see text][Formula: see text]mol/L, [Formula: see text]) to 136, 130 and 115[Formula: see text][Formula: see text]mol/L and 250, 188 and 152[Formula: see text][Formula: see text]mol/L in serum uric acid, correspondingly. In contrast to the evident renal toxicity of allopurinol, these preparations showed little impacts. Moreover, they showed some inhibitory effect on XOD (xanthine oxidase) activity. Compared with hyperuricemic control, protein expressions of OAT1 (organic anion transporter 1) were significantly elevated in AME- and AMW-treated mice. The levels of GLUT9 (glucose transporter 9) expression were significantly decreased by AMW. CNT2 (concentrative nucleoside transporter 2), a key target for purine absorption in gastrointestinal tract was involved in this study, and was verified for its innovative role. Both AME and AMW down-regulated CNT2 proteins in the gastrointestinal tract in hyperuricemic mice. As they exhibited considerable inhibitory effects on XOD, we selected XOD as the target for virtual screening by using molecular docking, and four compounds were hit with high ranks. From the analysis, we concluded that hydrogen bond, Pi–Pi and Pi-sigma interactions might play important roles for their orientations and locations in XOD inhibition.

scholarly journals A role for the organic anion transporter OAT3 in renal creatinine secretion in mice

2012 ◽  
Vol 302 (10) ◽  
pp. F1293-F1299 ◽  
Author(s):  
Volker Vallon ◽  
Satish A. Eraly ◽  
Satish Ramachandra Rao ◽  
Maria Gerasimova ◽  
Michael Rose ◽  
...  
Keyword(s):  
Organic Anion ◽  
Basolateral Membrane ◽  
Tubular Secretion ◽  
Organic Anion Transporter ◽  
Xenopus Laevis Oocytes ◽  
Mean Values ◽  
Anion Transporters ◽  
Anion Transporter ◽  
Neutral Compounds ◽  
Quantitative Contribution

Tubular secretion of the organic cation, creatinine, limits its value as a marker of glomerular filtration rate (GFR) but the molecular determinants of this pathway are unclear. The organic anion transporters, OAT1 and OAT3, are expressed on the basolateral membrane of the proximal tubule and transport organic anions but also neutral compounds and cations. Here, we demonstrate specific uptake of creatinine into mouse mOat1- and mOat3-microinjected Xenopus laevis oocytes at a concentration of 10 μM (i.e., similar to physiological plasma levels), which was inhibited by both probenecid and cimetidine, prototypical competitive inhibitors of organic anion and cation transporters, respectively. Renal creatinine clearance was consistently greater than inulin clearance (as a measure of GFR) in wild-type (WT) mice but not in mice lacking OAT1 ( Oat1−/−) and OAT3 ( Oat3−/−). WT mice presented renal creatinine net secretion (0.23 ± 0.03 μg/min) which represented 45 ± 6% of total renal creatinine excretion. Mean values for renal creatinine net secretion and renal creatinine secretion fraction were not different from zero in Oat1−/− (−0.03 ± 0.10 μg/min; −3 ± 18%) and Oat3−/− (0.01 ± 0.06 μg/min; −6 ± 19%), with greater variability in Oat1−/−. Expression of OAT3 protein in the renal membranes of Oat1−/− mice was reduced to ∼6% of WT levels, and that of OAT1 in Oat3−/− mice to ∼60%, possibly as a consequence of the genes for Oat1 and Oat3 having adjacent chromosomal locations. Plasma creatinine concentrations of Oat3−/− were elevated in clearance studies under anesthesia but not following brief isoflurane anesthesia, indicating that the former condition enhanced the quantitative contribution of OAT3 for renal creatinine secretion. The results are consistent with a contribution of OAT3 and possibly OAT1 to renal creatinine secretion in mice.

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.

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