scholarly journals Identification of a new gene product (diphor-1) regulated by dietary phosphate

1997 ◽  
Vol 273 (5) ◽  
pp. F801-F806 ◽  
Author(s):  
María Custer ◽  
Benjamin Spindler ◽  
François Verrey ◽  
Heini Murer ◽  
Jürg Biber
Keyword(s):  
Cellular Response ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Kidney Cortex ◽  
Rat Kidney Cortex ◽  
Reading Frame ◽  
New Gene ◽  
High Degree ◽  
The Impact ◽  
Kidney Proximal Tubules

Chronic restriction of dietary Pi elicits an increased reabsorption of Pi in the kidney proximal tubules, which involves a stimulation of apical Na-Pi cotansport. This adaptation is in part a direct cellular response of which the mechanism(s) are poorly understood. In this study, the impact of dietary Pi restriction on the differential expression of rat kidney cortex mRNAs was visualized to identify gene products regulated by the Pistatus. When kidney cortex mRNAs of rats fed a low- or a high-Pi diet were compared by differential display-polymerase chain reaction (DD-PCR), thirty modulated cDNA bands were observed, of which four were confirmed as being regulated. We focused on one of the upregulated bands, dietary Pi-regulated RNA-1 (diphor-1). A cDNA containing an open reading frame encoding a 52-kDa protein was cloned by library screening. Diphor-1 exhibits a high degree of identity to the Na/H exchanger regulatory factor and to a tyrosine kinase activating protein. Highest expression of diphor-1 mRNA was detected in the kidney (proximal tubules) and in small intestine. Expression experiments showed that diphor-1 specifically increases Na-Picotransport in oocytes of Xenopus laevis coinjected with renal type II Na-Pi cotransporter cRNA. Further characterizations of diphor-1 will show whether diphor-1 is primarily or secondarily involved in the response to dietary Pi.

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 Immunoelectron Microscopic Localization of the Electrogenic Na/HCO3 Cotransporter in Rat and Ambystoma Kidney

2000 ◽  
Vol 11 (12) ◽  
pp. 2179-2189
Author(s):  
ARVID B. MAUNSBACH ◽  
HENRIK VORUM ◽  
TAE-HWAN KWON ◽  
SØREN NIELSEN ◽  
BRIAN SIMONSEN ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Proximal Tubule ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Kidney Cortex ◽  
Apical Plasma Membrane ◽  
Rat Kidney Cortex ◽  
C Terminus ◽  
Basolateral Plasma Membrane ◽  
Intracellular Vesicles

Abstract. Immunofluorescence analysis has revealed that electrogenic Na+/HCO3- (NBC1) is expressed in the proximal tubule of rat kidney and in the proximal and distal tubules of the salamander Ambystoma tigrinum kidney. The present study was undertaken to define the detailed subcellular localization of the NBC1 in rat and Ambystoma kidney using high-resolution immunoelectron microscopy. For this purpose, two rabbit polyclonal antibodies raised against amino acids 928 to 1035 and amino acids 1021 to 1035 of the C-terminus of rat kidney (rkNBC1) were developed. The affinity-purified antibodies revealed a strong band of approximately 140 kD in immunoblots of membranes from rat kidney cortex but no signal in membranes isolated from outer and inner medulla. Deglycosylation reduced the apparent molecular weight to approximately 120 kD, corresponding to the predicted molecular weight. A similar but weaker band was also present in membranes isolated from the lateral part of Ambystoma kidney. In rat kidney, immunohistochemistry confirmed the presence of rkNBC1 in convoluted segments of the proximal tubules. In ultrathin cryosections or Lowicryl HM20 sections from rat kidney cortex, distinct immunogold labeling was associated with the basolateral plasma membrane of segments S1 and S2 of proximal tubules, whereas in S3 no labeling was observed. The labeling density was similar at the basal and lateral plasma membrane and was specifically associated with the inner surface of the membrane consistent with the internal position of the C-terminus of the transporter. In contrast, rkNBC1 was absent from the apical plasma membrane and not observed in intracellular vesicles, including those closely associated with basolateral plasma membrane. In Ambystoma kidney, a weak labeling was present in the basolateral membrane of the proximal tubule and stronger labeling was observed in the late distal segment. The results demonstrate that rkNBC1 is expressed only in segment S1 and segment S2 of rat proximal tubule as well as Ambystoma proximal and late distal tubule and that rkNBC1 is present in both basal and lateral plasma membranes and absent in intracellular vesicles of the apical plasma membrane.

Expression of Na-P(i) cotransport in rat kidney: localization by RT-PCR and immunohistochemistry

1994 ◽  
Vol 266 (5) ◽  
pp. F767-F774 ◽  
Author(s):  
M. Custer ◽  
M. Lotscher ◽  
J. Biber ◽  
H. Murer ◽  
B. Kaissling
Keyword(s):  
Transport System ◽  
Polyclonal Antibodies ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Expression Cloning ◽  
Kidney Cortex ◽  
Thick Ascending Limb ◽  
Rt Pcr ◽  
Rat Kidney Cortex ◽  
Proximal Tubular

We have recently identified a rat kidney cortex Na-dependent transport system for phosphate (P(i)) by expression cloning (NaP(i)-2) (S. Magagnin, A. Werner, D. Markovich, V. Sorribas, G. Stange, J. Biber, and H. Murer. Proc. Natl. Acad. Sci. USA 90: 5979, 1993). In this study we have used reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry to establish the sites of expression of the NaP(i)-2-related mRNA and protein. RT-PCR was performed with single microdissected nephron segments. From these experiments we conclude that NaP(i)-2 mRNA is predominantly expressed in the proximal tubules of superficial and deep nephrons. No NaP(i)-2 mRNA was detected in the thick ascending limb of Henle's loop; however, faint NaP(i)-2 related PCR products were also observed in collecting ducts. Expression of the NaP(i)-2 protein was examined with the use of polyclonal antibodies raised against synthetic NaP(i)-2-derived peptides. Strong specific anti-NaP(i)-2 antiserum-mediated immunofluorescence was found in the convoluted part of proximal tubules and gradually decreased along the straight part. Immunofluorescence indicated that the NaP(i)-2 protein is present in the brush border of proximal tubular cells. In addition, NaP(i)-2-specific immunofluorescence was also observed in subapical vesicles. The described distribution of the NaP(i)-2 protein is in agreement with previously described nephron sites of P(i) reabsorption in the rat kidney and therefore suggests that the NaP(i)-2 transport system represents an Na-P(i) cotransporter involved in proximal tubular apical transport of phosphate.

scholarly journals Transport ATPase cytochemistry: ultrastructural localization of potassium-dependent and potassium-independent phosphatase activities in rat kidney cortex.

1975 ◽  
Vol 66 (3) ◽  
pp. 586-608 ◽  
Author(s):  
S A Ernst
Keyword(s):  
Alkaline Phosphatase ◽  
Atpase Activity ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Rabbit Kidney ◽  
Kidney Cortex ◽  
Rat Kidney Cortex ◽  
Distal Tubules ◽  
Extracellular Side ◽  
Collecting Tubules

A cytochemical method for the light and electron microscope localization of the K- and Mg-dependent phosphatase component of the Na-K-ATPase complex was applied to rat kidney cortex, utilizing p-nitrophenylphosphate (NPP) as substrate. Localization of K-N-ATPase activity in kidneys fixed by perfusion with 1% paraformaldehyde -0.25% glutaraldehyde demonstrated that distal tubules are the major cortical site for this sodium transport enzyme. Cortical collecting tubules were moderately reactive, whereas activity in proximal tubules was resolved only after short fixation times and long incubations. In all cases, K-NPPase activity was restricted to the cytoplasmic side of the basolateral plasma membranes, which are characterized in these neplron segments by elaborate folding of the cell surface. Although the rat K-NPPase appeared almost completely insensitive to ouabain with this cytochemical medium, parallel studies with the more glycoside-sensitive rabbit kidney indicated that K-NPPase activity in these nephron segments is sensitive to this inhibitor. In addition to K-NPPase, nonspecific alkaline phosphatase also hydrolyzed NPP. The latter could be differentiated cytochemically from the specific phosphatase, since alkaline phosphatase was K-independent, insensitive to ouabain, and specifically inhibited by cysteine. Unlike K-NPPPase, alkaline phosphatase was localized primarily to the extracellular side of the microvillar border of proximal tubules. A small amount of cysteine-sensitive activity was resolved along peritubular surfaces of proximal tubules. Distal tubules were unreactive. In comparative studies, Mg-ATPase activity was localized along the extracellular side of the luminal and basolateral surfaces of proximal and distal tubules and the basolateral membranes of collecting tubules.

Cloning and functional expression of rNBC, an electrogenic Na+- HCO 3 − cotransporter from rat kidney

1998 ◽  
Vol 274 (2) ◽  
pp. F425-F432 ◽  
Author(s):  
Michael F. Romero ◽  
Peying Fong ◽  
Urs V. Berger ◽  
Matthias A. Hediger ◽  
Walter F. Boron
Keyword(s):  
Amino Acid ◽  
Rat Kidney ◽  
Basolateral Membrane ◽  
Functional Expression ◽  
Amino Acid Identity ◽  
Ambystoma Tigrinum ◽  
Kidney Cortex ◽  
Rat Kidney Cortex ◽  
Reading Frame ◽  
Major Route

We have recently cloned the renal electrogenic Na+-bicarbonate cotransporter of the salamander Ambystoma tigrinum(aNBC) (M. F. Romero, M. A. Hediger, E. L. Boulpaep, and W. F. Boron. FASEB J. 10: 89, 1996; and Nature 387: 409–413, 1997). Here we report the cloning of a mammalian homolog of aNBC, named rNBC for rat Na+-bicarbonate cotransporter. NBC constitutes the major route for[Formula: see text] reabsorption and assists in Na+ reabsorption across the basolateral membrane of the renal proximal tubule (PT). We used aNBC as a probe to screen a rat kidney cortex cDNA library in λgt10 and identified several clones. Each has an initiator Met and a large open-reading frame followed by a 3′-untranslated region of ∼500 bp. The 7.5-kb mRNA for rNBC is present in kidney, liver, lung, brain, and heart. In situ hybridization with the rNBC probe in the rat kidney revealed staining in the S2 segment of PT. rNBC encodes a protein of 1,035 amino acids, with a predicted molecular mass of 116 kDa. Its deduced amino acid sequence is 86% identical to that of aNBC. Comparison of both the aNBC and rNBC sequences to the GenBank database reveals a low level of amino acid identity (∼30%) to the AE family of Cl−/[Formula: see text]exchangers. Injection of rNBC cRNA into Xenopus oocytes leads to expression of an electrogenic Na+-[Formula: see text]cotransporter that is qualitatively similar to that of aNBC but at a much lower level. Placement of the rNBC cDNA into the context of a Xenopus expression vector produces a substantial increase in rNBC expression. Addition of 1.5% CO2/10 mM[Formula: see text] elicits a hyperpolarization of >50 mV and a rapid decrease of intracellular pH (pHi), followed by an increase in pHi. Subsequent removal of Na+ in the presence of CO2/[Formula: see text]causes a depolarization of >50 mV and a concomitant decrease of pHi. Thus rNBC is in the same newly identified family of Na+-linked[Formula: see text] transporters as is aNBC.

Evidence for mitochondrial origin of the HCO3(-)-ATPase in brush border membranes of rat proximal tubules

1985 ◽  
Vol 248 (3) ◽  
pp. F389-F395
Author(s):  
H. Knauf ◽  
M. Sellinger ◽  
K. Haag ◽  
U. Wais
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Brush Border ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Precipitation Method ◽  
Kidney Cortex ◽  
Marker Enzyme ◽  
Rat Kidney Cortex ◽  
Renal Tubular Cells

High HCO3(-)-ATPase activity is known to exist in mitochondria of renal tubular cells. In brush border membrane (BBM) preparations of proximal tubules such an anion-stimulated enzyme was also found. However, these preparations always contained mitochondrial markers. The putative localization and the role of this ATPase in BBM is still controversial. Some authors consider the HCO3(-)-ATPase in the BBM to be a mitochondrial contamination; others attribute to this ATPase a key role in H+ transport in the proximal tubule. To reinvestigate this problem, BBMs from rat kidney cortex were isolated by a simple, rapid (1.5-h) Ca2+-precipitation method, yielding a BBM fraction enriched 12.4-fold with respect to the marker enzyme leucine aminopeptidase (LAP). There was no basolateral Na+-K+-ATPase and no mitochondrial succinate dehydrogenase detectable. Cytochrome c oxidase was drastically reduced to 7 +/- 1% of that observed in the homogenate (TH). The activity of HCO3(-)-ATPase in the BBM fraction was 19 +/- 4 IU/g protein, i.e., 27% that of the homogenate. As sonication of the TH exclusively increases the activity of HCO3(-)-ATPase, its relative activity was 7.5% and thus equal to that of the mitochondrial marker. In many BBM preparations no HCO3(-)-ATPase was detectable. In those BBM preparations in which traces of HCO3(-)-ATPase were found, this activity coincided with that of cytochrome c oxidase in the respective preparation. There was a constant activity ratio of cytochrome c oxidase/HCO3(-)-ATPase in the TH, BBM, and pellet 1. The activity of HCO3(-)-ATPase in BBM did not depend on the activity of LAP.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Regeneration of renal proximal tubules after mercuric chloride injury is accompanied by increased binding of aminoacyl-transfer ribonucleic acid

1976 ◽  
Vol 160 (2) ◽  
pp. 357-365 ◽  
Author(s):  
D McEwen ◽  
K Ng
Keyword(s):  
Rat Kidney ◽  
Elongation Factor ◽  
Proximal Tubules ◽  
Supernatant Fraction ◽  
Kidney Cortex ◽  
Rat Kidney Cortex ◽  
Aminoacyl Transfer ◽  
Increased Activity ◽  
Elongation Factor 1 ◽  
Trna Binding

Homogenates of rat kidney cortex obtained 1,3 or 14 days after a single injection of HgCl2 were used to prepare the post-microsomal pH5 supernatant fraction. The activity of this fraction for peptide synthesis from [14C]phenylalanyl-tRNA was significantly increased at 1 and 3 days, at which time the proximal tubules are regenerating [Cuppage & Tate (1967) Am. J. Pathol. 51, 405-429]. This increased activity could not be attributed to a decreased inhibitory activity, but was due to an increased aminoacyl-tRNA binding, i.e. elongation-factor-1 activity, in the supernatant fraction.

scholarly journals Increase of Na/Pi-cotransport encoding mRNA in response to low Pi diet in rat kidney cortex.

1994 ◽  
Vol 269 (9) ◽  
pp. 6637-6639
Author(s):  
A. Werner ◽  
S.A. Kempson ◽  
J. Biber ◽  
H. Murer
Keyword(s):  
Rat Kidney ◽  
Kidney Cortex ◽  
Rat Kidney Cortex
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