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标题: Immunolocalization of a microsomal prostaglandin E synthase in rabbit kidney [打印本页]

作者: 轻羽    时间: 2009-4-21 13:42     标题: Immunolocalization of a microsomal prostaglandin E synthase in rabbit kidney

作者:Amanda L. Fuson, Peter Komlosi, Tino M. Unlap, P. Darwin Bell,  János Peti-Peterdi作者单位:Nephrology Research and Training Center, Division of Nephrology,Department of Medicine, University of Alabama at Birmingham, Birmingham,Alabama 35294 . s+ G& {$ h) [, ^
                  
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          【摘要】
: }  W9 A3 @1 k& w1 P! J; m$ |8 D      PGE 2, the major cyclooxygenase (COX) metabolite of arachidonic acid, is an important paracrine regulator of numerous tubular and vascularfunctions in the kidney. To date, COX activity has been considered the keystep in prostaglandin synthesis and is well characterized. However, much lessis known about the recently cloned microsomal PGE 2 synthase(mPGES), the terminal enzyme of PGE 2 synthesis, which convertsCOX-derived PGH 2 to the biologically important PGE 2.Present studies provide the detailed localization of mPGES protein in therabbit kidney using immunohistochemistry. In the cortex, strong mPGES labeling was found in the macula densa (MD) and principal cells of the connectingsegment and cortical collecting tubule but not in intercalated cells. Themedulla was abundant in mPGES-positive structures, with heavy labeling in thecollecting duct system. In descending thin limbs and renal medullaryinterstitial cells, mPGES expression was less intense, and it was below thelimits of detection in the vasa recta. Expression of MD mPGES, similarly toCOX-2, was greatly increased in response to low-salt diet and angiotensinI-converting enzyme inhibition by captopril. These findings suggest autocrineregulation of renal salt and water transport by PGE 2 in descendingthin limb and collecting tubule and a paracrine effect of PGE 2 onthe glomerular and medullary vasculature. Similar to other organs, mPGES inthe kidney is an inducible enzyme and may be similarly regulated and acts inconcert with COX-2.
8 v6 \7 b: ^! P* H/ {. c  B8 `          【关键词】 membraneassociated prostaglandin E synthase cyclooxygenase macula densa collecting duct principal cells descending thin limb immunohistochemistry7 f" Y8 O3 Y: W. \  K8 ]  @
                  PGE 2 IS BY FAR the major prostanoid synthesized inthe kidney and is an important paracrine regulator of salt and waterhomeostasis ( 1 - 5, 8, 13, 14, 24 ). PGE 2 regulatestubular transport of Na   and water, resulting in natriuresis anddiuresis ( 1, 24 ). As a potent vasodilator,it helps to maintain glomerular filtration and medullary blood flow inconditions associated with decreased renal perfusion( 1, 13, 24 ) and/or high renin levels( 13, 14, 24 ). Another importanttubulovascular function is PGE 2 production by macula densa (MD)cells ( 22, 23 ) in signaling low distaltubular NaCl concentration-induced renin release( 25 ). Because PGE 2 acts only in the immediate vicinity of its site of generation, it is veryimportant to know which nephron segments synthesize this autacoid. Previousenzyme immunoassay measurements, using microdissected tubule segments ( 1, 8 ) from rabbit kidney, detectedlarge amounts of PGE 2 synthesized in the descending thin limb andthe collecting duct system. However, these assays were not able to analyze short tubular segments like the MD and could not identify the exact celltype(s) of tubules, vascular or interstitial structures where PGE 2 may be synthesized. Localization of the synthetic machinery necessary forPGE 2 production could provide further insights into where thisautacoid is produced.
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* j; B" F+ b! N8 b' R3 ?To date, cyclooxygenase (COX) activity has been considered the key step inprostaglandin synthesis and the localization of two isoforms, COX-1 and COX-2,has been well characterized in the kidney( 4, 9, 10, 13, 14, 26 ). However, metabolism ofarachidonate by either COX-1 or COX-2 yields only the unstable intermediaryPGH 2 ( 2, 3, 14, 16, 18, 19 ). The subsequent fate ofPGH 2 is dictated by coexpression of a prostaglandin synthase, theother key enzyme of prostaglandin synthesis, which is capable of convertingPGH 2 to one of the prostanoid end products includingPGE 2, PGF 2a, PGD 2, PGI 2, andTxA 2 ( 2, 3, 14, 27 ). Recently, themembrane-associated PGE synthase (mPGES), a terminal enzyme of PGE 2 biosynthesis, has been cloned ( 16, 18 ). Renal mRNA expression formPGES was recently described in microdissected tubular segments of the ratkidney and in the mouse ( 12, 27 ). Also, very recent workdescribed the site-specific expression of key enzymes for prostaglandinsynthesis, including mPGES, in rodent kidney( 6 ). However, to date, there isno information on the renal regulation of mPGES protein and its localizationin the rabbit kidney. We therefore analyzed, in detail, the sites of mPGESprotein expression in the rabbit kidney and its regulation in the MD usingimmunofluorescence.
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MATERIALS AND METHODS+ o! h) W7 V' ^6 B0 g- J) A
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Salt Diet and Captopril+ w& r& f5 A% E6 S
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Separate groups of New Zealand White rabbits (0.5-1.0 kg, Myrtle) were fedstandard (8630 Harlan Teklad, Madison, WI, 0.3% NaCl), low-salt (TD 90188,0.01% NaCl), or high-salt (TD 98164, 7.7% NaCl) rabbit chow for a minimum of 1wk. A separate group of rabbits received captopril (Sigma, St. Louis, MO) inthe drinking water (500 mg/l) for 7 days.- T4 b  Y# [, Q( ?. ~: g, }7 G
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Immunohistochemistry1 d; e6 i% v+ P. g  \7 C8 ]
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Fixation and preparation of tissue for immunohistochemistry. Five-hundred-gram female New Zealand White rabbits were anesthetized withpentobarbital sodium, and the kidneys were perfusion-fixed by first insertinga cannula into the descending aorta distal to the renal arteries. The kidneyswere then perfused retrograde first with PBS, pH 7.4, at 37°C to removeblood, followed by 4% paraformaldehyde in Dulbecco's modified Eagle's/F-12 medium. The kidneys were then removed, and coronal kidney sections wereincubated overnight at 4°C in 4% paraformaldehyde and then embedded inparaffin.
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# T0 s: t$ w( s2 h* w4 lSectioning and immunolabeling. Subsequently, 4-µm-thick sections of the paraffin block were deparaffinized with toluene, washed ingraded ethanol, and rehydrated in PBS. Sections were subjected to microwaveantigen retrieval before staining and blocked with PBS-Tween for 20 mincontaining 2% goat serum to lower background fluorescence. Subsequent blockingwith goat anti-rabbit Fab IgG (1:100, Jackson ImmunoResearch Laboratories, West Grove, PA) was carried out for 40 min to reduce nonspecific binding whena rabbit polyclonal antibody (anti-mPGES) was used on rabbit tissue. Aftersubsequent washings in PBS, tissues were treated with the affinity-purifiedrabbit polyclonal mPGES antibody (1:50, Cayman Chemical, Ann Arbor, MI). Afterbeing washed, there was a 40-min incubation with Alexa Fluor 594-conjugated goat anti-rabbit IgG (1:500, Molecular Probes, Eugene, OR). Sections weremounted with Vecta-shield media, containing 4,6-diamino-2-phenylindole (DAPI)for nuclear staining (Vector Laboratories, Burlingame, CA). Tissue sectionswere examined with an Olympus IX70-inverted epifluorescence microscope using aUApo/340 x 40 objective. Images were captured using a SenSys digitalcamera and IPLab Spectrum software equipped with power microtome (SignalAnalytics).* @* C5 h6 `# C9 w% C

; s% h  A. K5 NDouble labeling mPGES with aquaporin-1 or -2. Some of the kidney sections were double labeled with anti-mPGES and anti-aquaporin (AQP)-1 orAQP2 antibodies. After blocking for 20 min with 2% donkey serum in PBS-Tween,there was a subsequent blocking with goat anti-rabbit Fab IgG (1:100, JacksonImmunoResearch Laboratories) for 40 min to reduce nonspecific binding. After being subsequently washed with PBS-Tween, tissues were treated with either agoat polyclonal AQP1 or AQP2 antibody (L-19 and C-17, respectively, 1:100,Santa Cruz Biotechnology, Santa Cruz, CA) for 1 h. The tissue was then washedand subsequently incubated with an Alexa Fluor 594-conjugated donkey anti-goat IgG (1:500, Molecular Probes) for 40 min. Sections were then washed andsubsequently incubated with affinity-purified mPGES polyclonal antibody (1:50,Cayman Chemical) for 1 h. After being washed, sections were incubated for 40min with Alexa Fluor 488-conjugated goat anti-rabbit IgG (1:500, Molecular Probes). Sections were washed and mounted with Vecta-shield media, containingDAPI for nuclear staining (Vector Laboratories). Tissue sections were examinedas described earlier.& F8 ]) Y0 u) J* m
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COX-2 immunofluorescence. Rabbit kidney sections were prepared asdescribed above. For labeling, tissues were treated with either a goatpolyclonal COX-2 antibody (C-20, 1:100, Santa Cruz Biotechnology) overnight orwith the affinity-purified rabbit polyclonal mPGES antibody (1:50, CaymanChemical). After being washed, there was a 40-min incubation with Alexa594-conjugated donkey anti-goat IgG (1:500, Molecular Probes) for COX-2sections or with Alexa 488-conjugated goat anti-rabbit IgG (1:500, Molecular Probes) for mPGES sections.& r4 M& c# S1 X' T  t4 A8 @- J
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Immunolabeling controls. The following controls were performed: 1 ) adsorption controls made by incubation with affinity-purified mPGES polyclonal antibody (10 µg/ml) previously reacted with purified mPGESprotein (100 µg/ml) that was used for immunization (Cayman Chemical) and 2 ) incubation without the use of primary antibodies. All controlsrevealed an absence of labeling.$ Z, w6 e( T" g5 `1 |3 _

  D3 i5 P/ x# O3 N; r3 J' qRESULTS
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Localization of mPGES in the Renal Cortex
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Overall expression of the mPGES protein in the cortex( Fig. 1 A ) was muchlower than in the medulla ( Fig.1 B ) and was confined to only short or isolated tubulesegments in the distal nephron. Fluorescence labeling was specific, becauseomitting or blocking the primary antibody with the mPGES protein (data notshown) resulted in no staining. Also, labeling was present throughout thecytoplasm and was confined to small granules, consistent with microsomallocalization. Strong labeling for mPGES was found in the macula densa( Fig. 2 A ), surroundingcortical thick ascending limb cells, in the connecting segment (CNT), and inthe cortical collecting duct (CCD; Fig.2 B ). No staining was detected in the proximal or distalconvoluted tubules, in the glomerulus, or in vascular structures. Carefulanalysis revealed that only a subpopulation of cells in the CNT and CCD ( Fig. 2 B ) wasimmunoreactive. Double labeling with an AQP2 antibody that selectively bindsto mainly the apical membrane of principal cells (PC) found that mPGES proteinwas localized only in PC of CNT and CCD( Fig. 2 C ) and labelingwas below the limits of detection in intercalated (IC) cells.6 T; L% ~  ~* @' I$ s6 ^4 V7 z; Q

( H5 i8 W6 I7 P! L! T9 E$ [  \Fig. 1. Overview of microsomal PGE 2 synthase (mPGES) immunofluorescencestaining (red) in the renal cortex ( A ) and medulla ( B ).Magnification x 200; nuclei are blue.
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9 I& l* N$ n. M) l: w7 F* @2 e- HFig. 2. Immunohistochemical localization of mPGES (red) in the renal cortex. A : macula densa (arrowhead) region with surrounding cortical thinascending limb (cTAL) and glomerulus (G). B : connecting segment (CNT)and cortical collecting duct (CCD; arrowheads point at individual cells devoidof staining). C : double labeling of mPGES (green) and aquaporin(AQP)2 (red) in CCD. Intercalated cells (arrowheads) were not immunoreactive,whereas principal cells were labeled with both the mPGES antibody (green,throughout the cells) and AQP2 (red, mainly at the apical membrane).Magnification x 400 ( A - C ) and x 1,000( D ); nuclei are blue.
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Localization of mPGES in the Renal Medulla6 }% a9 U# i4 }! N9 S( f. [4 ?8 Q
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The medulla was abundant in mPGES-immunoreactive structures. In the outermedulla, descending thin limbs (DTL; Fig.3, A - E ) and medullary collecting ducts (MCD; Fig. 3, C - E )displayed strong labeling. Similar to the distinct localization of mPGEs inthe CCD, only a subpopulation of cells in the outer MCD ( Fig. 3 E ) wasimmunoreactive. mPGES-positive cells, similar to CCD, also labeled with AQP-2,indicated a PC phenotype (not shown). No evidence for mPGES was found indescending vasa recta (DVR; Fig. 3, B and E ). Vasa recta was identified by red bloodcells in the lumen and also based on their expression of the AQP1 waterchannel. Double labeling with an AQP1 antibody that selectively binds to DTLsegments and vasa recta revealed that mPGES protein was localized only in DTLsand not in DVR or ascending thin limbs( Fig. 3 E ). In theinner medulla, heavy labeling of mPGES in MCD continued to the papilla. Inaddition to MCD, numerous thin-walled tubular structures were immunoreactive ( Fig. 3 D ), resemblingthe terminal part of long DTLs. mPGES was also localized to renal medullaryinterstitial cells (RMIC; Fig.3 D ).5 s. r1 I# _- r4 T7 O

3 z0 Z! E% z4 O; u. gFig. 3. Immunohistochemical localization of mPGES (red) in the renal medulla. A : transition of a straight proximal tubule (S3), devoid of staininginto the strongly labeled outer medullary descending thin limb (DTL). B : mPGES expression in the vasa recta next to DTL (arrow indicatesmPGES-positive red blood cells in the lumen) was below the limits ofdetection. C : CCDs next to DTLs. D : renal medullaryinterstitial cells (RMIC) near the papilla, around heavily labeled medullarycollecting ducts (MCD) and numerous thin-walled tubular structures (DTL). E : double labeling of mPGES (green) and AQP1 (red) in the medullademonstrates colocalization in DTLs (yellow), whereas descending vasa recta(DVR) was positive only for AQP1 (red) and CCD only for mPGES (green).Magnification x 400; nuclei are blue.& ^  O( ~+ o4 o

  s) p9 n4 O/ E) uRegulation of MD mPGES Protein Expression by Salt Diet andCaptopril
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Because mPGES is considered as an inducible enzyme similar to COX-2, wetested whether well-defined stimuli for COX-2, such as changes in salt intakeand angiotensin I-converting enzyme (ACE) inhibition by captopril, would alsoregulate mPGES expression in the MD segment of renal cortex. Figure 4 demonstrates that mPGES and COX-2 were colocalized in the MD segment. A low-salt dietsignificantly increased the number of both COX-2- and mPGES-immunoreactive MDcells per MD plaque ( 5.5- and 3-fold, respectively, n = 6 MDplaques in each group, P High-salt intake caused smallreductions in both COX-2 and mPGES expression( Fig. 4 ). ACE inhibition withcaptopril, similar to low-salt diet, greatly increased the expression of bothCOX-2 and mPGES in the MD ( 8- and 3.5-fold, respectively, P with control tissue,was observed in response to varying salt intake and captopril treatmentincluding expression in PC of the collecting tubule.+ x- G- Q/ O3 E9 B) h

; Z  j1 A: X) t+ N2 T: UFig. 4. Immunohistochemical localization of cyclooxygenase (COX)-2 (red) and mPGES(green) in the macula densa (arrowhead) on normal-, low-salt (LS), andhigh-salt (HS) diets and after captopril (Cap) treatment ( A ). B : statistical summary of the number of immunoreactive MD cells perMD plaque in the same groups ( n = 6 each).. L" D3 S& X; C' j

8 m7 N, ^4 c/ ]7 S/ o. T2 \DISCUSSION
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; D1 D) t& S+ s: [! gThe present study provides a detailed description of the localization ofmPGES protein in the rabbit kidney ( Fig.5 ). In contrast to the renal cortex, a high level of mPGESexpression was found in the medulla, the major site of PGE 2 synthesis ( 1, 24 ). Strong labeling in thecollecting duct system and DTL is also consistent with earlier enzymeimmunoassay measurements ( 1, 8 ), demonstrating that thesenephron segments are the major sites of PGE 2 synthesis in thekidney. However, this enzyme immunoassay( 8 ) used isolated nephronsegments microdissected from rabbits, the same species we used forimmunohistochemistry, so there was no information obtained from vascularstructures and the interstitium. Also, the use of dissected tubules( 8, 27 ) or cell cultures withmixed phenotype ( 7, 9 ) did not allow comparisonbetween different cell types within the individual segments. Presentimmunolocalization data are similar to findings of a very recent report( 6 ) that described thesite-specific expression of key enzymes for renal prostaglandin synthesis inrodent kidney. The only exception seems to be the significant mPGES expressionin the DTL in rabbit kidney that was apparently not present in rat andmouse.
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  |. _3 [. U  c- T0 i  hFig. 5. Schematic representation of mPGES expressing renal structures (dark areas)in rabbit kidney. DT, distal tubule; PT, proximal tubule; TAL, thick ascendinglimb.! K2 e: n& n4 L2 O4 k0 H
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This study is an extension of our recent work that detected PGE 2 release from MD cells and first described, in preliminary form, thelocalization of mPGES in MD cells( 22, 23 ). Expression of mPGES inthe MD is consistent with the presence of COX-2 in these cells( 4, 13, 23, 25, 28 ) and also withPGE 2 production and release from MD cells( 22, 23 ). However, a recent reportfailed to detect mPGES mRNA in MD cells from the rat kidney( 27 ). These conflictingresults may represent different sensitivities of methods used. Identificationof PC in the collecting tubule was based on double labelingimmunohistochemistry using an AQP2 antibody that selectively binds to mainlythe apical membrane of PC in various species( 17, 20 ). Consistent with this, wefound strong AQP2 labeling of PC at the apical membrane( Fig. 2 C )." X) f  R/ C$ q0 W

. L/ w9 \& J% A0 fDistinct localization of mPGES in PC but not in IC cells has not beenreported previously. Each of the PGH 2 -producing COX isoforms, butparticularly COX-1, is expressed in the collecting duct system; however, thelocalization seems to be species, cell type, and physiological statusdependent ( 4, 9, 13, 14, 26 ). A high level ofPGE 2 synthesis was detected in both isolated CCD and MCD( 8 ), and there arewell-established inhibitory effects of PGE 2 on PC Na   and water transport ( 1 ).However, there are no known specific effects of PGE 2 on IC cells,except that a recent report suggested, indirectly, the presence of a PGEreceptor [most likely E prostanoid (EP) receptor EP 3 ] in thesecells ( 15 ). At present, thefunctional importance of this distinct mPGES localization in the CCD and OMCDis not known. It is possible that other as yet to be localized PGE synthaseisoforms ( 18 ) are alsoexpressed in the collecting tubule and participate in PGE 2 biosynthesis. Understanding the role of PC-specific, mPGES-derivedPGE 2 synthesis on collecting tubule function will require knowledgeof cell-specific expression of different EP receptors in this nephron segment.PGE 2 interacts with four different G protein-coupled EP receptorsdesignated EP 1, EP 2, EP 3, and EP 4 ( 2, 3 ), and all of these receptors appear to be expressed in the collecting tubule( 3, 11 ). Thus PGE 2 synthesis by COX and PGES isoforms may exert local autocrine or paracrineactions in the collecting tubule via one or more of these receptors, and thiscomplex interaction needs to be further investigated.* ?8 {( O5 t; B
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Expression of mPGES in the DTL is consistent with earlier work ( 8 ) that detected significantPGE 2 synthesis in individual DTLs microdissected from the rabbitkidney. It has been suggested that PGE 2, synthesized in thissegment, may regulate tubular transport( 1, 8 ), but it may also influencemedullary blood flow by acting on nearby pericytes of DVR( Fig. 2 E ).Identification of DVR was based on the presence of red blood cells in the lumen ( Fig. 3 B ) anddouble labeling immunohistochemistry using an AQP1 antibody that selectivelybinds to DTL and DVR ( 21 ). Consistent with this, we found strong AQP1 labeling in these structures( Fig. 3 D ). Absence ofmPGES in DVR ( Fig. 3, B and E ) suggests that this vascular segment cannot synthesizePGE 2; however, it does not rule out that PGE 2 productionby DTL, MCD, and medullary interstitial cells may cause DVR vasodilation andan increase in medullary blood flow. Indeed, mPGES labeling was intense inRMIC ( Fig. 3 D ), aspecial cell type in the medulla that expresses COX-2( 10 ) and interconnects tubular structures with each other and with vasa recta. The absence of mPGES labelingin both cortical and medullary vascular structures, but its presence inadjacent tubular segments and cell types, suggests a paracrine effect forPGE 2 on renal hemodynamics.( U# n( u; Q+ K: t

: z4 G: y/ M% rThe present studies also demonstrated that mPGES, an enzyme capable ofconverting COX-2-derived PGH 2 to PGE 2, was not only present in the rabbit MD ( Fig.2 A ) but that it colocalizes with COX-2 in these cells( Fig. 4 ). In addition, weexamined if well-established stimuli for COX-2 (i.e., changes in salt intakeand ACE inhibition) would also induce mPGES expression. We found that MDexpression of both COX-2 and mPGES was greatly upregulated in response tolow-salt intake and ACE inhibition by captopril( Fig. 4 ). Also, high-saltintake caused a small reduction in COX-2 and mPGES staining in the MD. Thesefindings indicate that, consistent with other cell types( 16, 18, 19 ), mPGES in the MD is aninducible enzyme, similar to COX-2. Low-salt intake upregulates cortical COX-2expression in various species including rabbit( 14, 28 ). Colocalization of COX-2 and mPGES in the MD and their upregulation by a low-salt diet support thenotion that these enzymes share a common gene-regulatory mechanism( 16, 18, 19 ) and may contribute to theincrease in PGE 2 synthesis associated with stress, inflammatory,and pyretic responses. Consistent with these immunofluorescence findings,recent functional experiments using a biosensor technique ( 22, 23 ) demonstrated significantlyincreased PGE 2 release from MD cells on a low-salt diet, comparedwith normal-salt intake. Further work is needed to characterize the regulation of mPGES expression in response to various other stimuli and in the renalmedulla.& m" I2 Y* z. _4 s) `9 t

& o' P+ A' z6 d$ B- QIn summary, the present studies localized a PGES in DTL, MD, and PC of thecollecting duct system and medullary interstitial cells in the rabbit kidney.Regulation of the mPGES protein expression by various salt diets and ACEinhibition suggests that mPGES is an inducible enzyme, similar to COX-2.Understanding the importance and complex effects of PGE 2 synthesized by mPGES at these sites of the nephron requires furtherstudies.
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( A; D8 D% V% R3 {2 O/ e) iDISCLOSURES
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7 B4 v8 W% r; s7 C" g/ q1 N$ gThis work was supported by grants from National Institute of Diabetes andDigestive and Kidney Diseases (32032) to P. D. Bell and American HeartAssociation SDG (0230074N) and ASN Carl W. Gottschalk Research Scholar Grantto J. Peti-Peterdi.
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  ?1 H4 v$ A% {) |/ c5 gACKNOWLEDGMENTS! L% M) C1 e% J. [4 |0 }% S

  [2 B6 o( Q9 ~We thank J. Hosmer, University of Alabama at Birmingham (UAB) AnimalResources Program, Histology Division, for excellent technical assistance withtissue processing and sectioning. Also, the authors thank A. Tousson and S.Williams at UAB High Resolution Imaging Facility for help with fluorescenceimaging.
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* ]0 ^; y+ r' W5 ?% KGuan Y, ZhangY, Schneider A, Riendeau D, Mancini JA, Davis L, Kömhoff M, Breyer RM,and Breyer MD. Urogenital distribution of a mouse membrane-associatedprostaglandin E 2 synthase. Am J Physiol RenalPhysiol 281:F1173-F1177, 2001.
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& H! _6 g3 C- G: k& VHarris RC Jr. Cyclooxygenase-2 inhibition and renal physiology. Am JCardiol 89:10D-17D, 2002.& w% v0 B, v$ h9 V
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0 q* B/ G! Y: ~' E: gHarris RC andBreyer MD. Physiological regulation of cyclooxygenase-2 in the kidney. Am J Physiol Renal Physiol 281:F1-F11, 2001.' Y* i* X, ]  ~' q7 E4 o5 B1 n
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( p' K& M# I8 J( RHelies-Toussaint C, Aarab L, Gasc JM, Verbavatz JM, and ChabardesD. Cellular localization of type 5 and type 6 ACs in collecting duct andregulation of cAMP synthesis. Am J Physiol RenalPhysiol 279:F185-F194, 2000.
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3 T" O. }! U7 {Jakobsson PJ,Thoren S, Morgenstern R, and Samuelsson B. Identification of humanprostaglandin E synthase: a microsomal, glutathione-dependent, inducibleenzyme, constituting a potential novel drug target. Proc Natl AcadSci USA 96:7220-7225, 1999.
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Loffing J,Loffing-Cueni D, Macher A, Hebert SC, Olson B, Knepper MA, Rossier BC, andKaissling B. Localization of epithelial sodium channel and aquaporin-2 inrabbit kidney cortex. Am J Physiol Renal Physiol 278: F530-F539,2000.0 d5 E( l; P! F+ S6 {

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/ T+ X# I( F' Q; K6 I. m* MMurakami M,Naraba H, Tanioka T, Semmyo N, Nakatani Y, Kojima F, Ikeda T, Fueki M, Ueno A,Oh-Ishi S, and Kudo I. Regulation of prostaglandin E 2 biosynthesis by inducible membrane-associated prostaglandin E 2 synthase that acts in concert with cyclooxygenase-2. J BiolChem 275:32783-32792, 2000.5 x- f) d5 M- e; \5 o2 Y/ N
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作者: MIYAGI    时间: 2015-6-11 07:10

太棒了!  
作者: 榴榴莲    时间: 2015-6-13 07:59

干细胞库  
作者: xuguofeng    时间: 2015-7-5 21:09

挺好啊  
作者: 榴榴莲    时间: 2015-8-10 12:53

淋巴细胞
作者: 杏花    时间: 2015-8-12 17:50

慢慢来,呵呵  
作者: 陈晴    时间: 2015-9-2 04:59

干细胞我这辈子就是看好你
作者: s06806    时间: 2015-9-9 22:10

支持一下吧  
作者: 泡泡鱼    时间: 2015-9-29 12:24

我帮你 喝喝  
作者: txxxtyq    时间: 2015-10-8 03:35

免疫细胞治疗  
作者: immail    时间: 2015-10-23 14:43

说的不错  
作者: beautylive    时间: 2015-11-13 20:53

似曾相识的感觉  
作者: awen    时间: 2015-11-22 20:26

你加油吧  
作者: dypnr    时间: 2015-12-11 23:10

不错!  
作者: tuanzi    时间: 2015-12-12 12:24

昨晚多几分钟的准备,今天少几小时的麻烦。  
作者: bluesuns    时间: 2015-12-21 09:34

厉害!强~~~~没的说了!  
作者: yukun    时间: 2015-12-28 17:10

顶下再看  
作者: xuguofeng    时间: 2015-12-29 21:10

我顶啊。接着顶  
作者: sky蓝    时间: 2015-12-31 14:39

干细胞之家是国内最好的干细胞网站了
作者: 橙味绿茶    时间: 2015-12-31 16:10

不错不错.,..我喜欢  
作者: xuguofeng    时间: 2016-1-6 18:57

不错啊! 一个字牛啊!  
作者: 昕昕    时间: 2016-2-1 13:00

真是佩服得六体投地啊  
作者: MIYAGI    时间: 2016-2-7 11:09

也许似乎大概是,然而未必不见得。  
作者: 我学故我思    时间: 2016-3-20 15:35

哈哈,看的人少,回一下  
作者: biobio    时间: 2016-4-15 11:54

我也来顶一下..  
作者: doors    时间: 2016-4-22 15:27

呵呵,等着就等着....  
作者: Greatjob    时间: 2016-5-22 15:10

有才的不在少数啊  
作者: abc987    时间: 2016-7-5 20:23

我也来顶一下..  
作者: abc987    时间: 2016-8-8 14:18

我的啦嘿嘿  
作者: xiao2014    时间: 2016-9-19 12:01

呵呵 高高实在是高~~~~~  
作者: htc728    时间: 2016-9-22 11:35

也许似乎大概是,然而未必不见得。  
作者: 红旗    时间: 2016-11-7 19:33

这贴?不回都不行啊  
作者: 罗马星空    时间: 2016-11-9 22:43

一定要回贴,因为我是文明人哦  
作者: biodj    时间: 2016-11-12 19:09

我回不回呢 考虑再三 还是不回了吧 ^_^  
作者: 分子工程师    时间: 2016-11-28 18:10

不错,感谢楼主
作者: 蚂蚁    时间: 2016-12-4 00:31

勤奋真能造就财富吗?  
作者: dmof    时间: 2016-12-28 16:07

这贴?不回都不行啊  
作者: qibaobao    时间: 2017-1-8 06:54

看完了这么强的文章,我想说点什么,但是又不知道说什么好,想来想去只想  
作者: 苹果天堂    时间: 2017-1-17 07:35

站个位在说  
作者: 求索迷茫    时间: 2017-2-24 05:50

这贴子你会收藏吗  
作者: 咖啡功夫猫    时间: 2017-2-27 11:43

回帖是种美德.  
作者: 小丑的哭泣    时间: 2017-3-12 17:52

说的不错  
作者: youngcell    时间: 2017-3-21 00:27

只有一条路不能选择——那就是放弃的路;只有一条路不能拒绝——那就是成长的路。  
作者: 365wy    时间: 2017-3-21 02:08

先看看怎么样!  
作者: highlight    时间: 2017-3-21 07:17

家财万贯还得回很多贴哦  
作者: biopxl    时间: 2017-3-28 08:43

天啊. 很好的资源
作者: 水木清华    时间: 2017-4-4 12:53

看或者不看,贴子就在这里,不急不忙  
作者: ines    时间: 2017-4-8 03:47

干细胞研究重在基础
作者: www1202000    时间: 2017-4-19 15:27

真是天底下好事多多  
作者: 小小C    时间: 2017-5-11 15:02

楼上的稍等啦  
作者: 锦锦乐道    时间: 2017-5-13 19:34

慢慢来,呵呵  
作者: myylove    时间: 2017-6-3 22:00

赚点分不容易啊  
作者: 舒思    时间: 2017-6-10 08:45

不错,感谢楼主
作者: dmof    时间: 2017-6-30 02:19

我帮你 喝喝  
作者: HongHong    时间: 2017-7-11 05:54

嘿嘿......哈哈......呵呵.....哟~呼  
作者: 甘泉    时间: 2017-7-19 20:24

楼上的稍等啦  
作者: Greatjob    时间: 2017-8-5 23:27

琴棋书画不会,洗衣做饭嫌累。  
作者: 小倔驴    时间: 2017-8-20 18:37

说的不错  
作者: 生物小菜鸟    时间: 2017-9-15 04:12

每天到干细胞之家看看成了必做的事情
作者: 123456zsz    时间: 2017-10-2 13:46

今天临床的资料更新很多呀
作者: txxxtyq    时间: 2017-11-2 12:26

表观遗传学
作者: dypnr    时间: 2017-11-9 16:09

干细胞存储  
作者: yukun    时间: 2017-11-13 11:35

好人一个  
作者: 桦子    时间: 2017-11-19 06:31

回贴赚学识,不错了  
作者: 小倔驴    时间: 2017-11-22 22:47

人气还要再提高  
作者: 石头111    时间: 2017-12-22 02:07

加油站加油  
作者: 分子工程师    时间: 2017-12-22 09:54

我喜欢这个贴子  
作者: 我学故我思    时间: 2018-1-12 21:07

淋巴细胞
作者: 泡泡鱼    时间: 2018-1-13 21:51

呵呵 高高实在是高~~~~~  
作者: 依旧随遇而安    时间: 2018-1-20 15:49

老大,我好崇拜你哟  
作者: dglove    时间: 2018-1-26 02:57

不错,看看。  
作者: 依旧随遇而安    时间: 2018-2-12 09:35

不错,支持下  
作者: 再来一天    时间: 2018-2-15 05:36

看看..  
作者: heart10    时间: 2018-2-16 11:54

哈哈,看的人少,回一下  
作者: leeking    时间: 2018-3-6 13:00

呵呵 都没人想我~~  
作者: bluesuns    时间: 2018-3-7 09:27

我又回复了  
作者: tian2006    时间: 2018-3-27 14:27

呵呵,等着就等着....  
作者: na602    时间: 2018-4-6 12:25

好 好帖 很好帖 确实好帖 少见的好帖  
作者: syt7000    时间: 2018-4-9 20:27

彪悍的人生不需要解释。  
作者: dd赤焰    时间: 2018-4-27 16:10

很有吸引力  
作者: MIYAGI    时间: 2018-5-7 19:56

我仅代表干细胞之家论坛前来支持,感谢楼主!  
作者: 咖啡功夫猫    时间: 2018-5-21 05:42

干细胞行业门户 干细胞之家
作者: biobio    时间: 2018-5-25 13:27

好困啊  
作者: DAIMAND    时间: 2018-5-26 17:42

呵呵,明白了  
作者: kaikai    时间: 2018-5-27 11:27

初来乍到,请多多关照。。。嘿嘿,回个贴表明我来过。  
作者: 水木清华    时间: 2018-6-18 13:17

哈哈 我支持你
作者: apple0    时间: 2018-6-27 05:37

不要等到人人都说你丑时才发现自己真的丑。  
作者: youngcell    时间: 2018-7-3 17:25

干细胞治疗糖尿病  
作者: netlover    时间: 2018-7-15 03:07

围观来了哦  
作者: 365wy    时间: 2018-7-29 12:18

不错不错.,..我喜欢  
作者: biopxl    时间: 2018-8-7 09:43

呵呵,找个机会...  
作者: 再来一天    时间: 2018-8-9 13:27

加油啊!!!!顶哦!!!!!  
作者: 温暖暖    时间: 2018-8-9 18:04

干细胞研究重在基础
作者: ladybird    时间: 2018-8-27 13:54

拿分走人呵呵,楼下继续!
作者: marysyq    时间: 2018-9-14 13:10

今天无聊来逛逛  
作者: 天蓝色    时间: 2018-9-19 17:20

真是有你的!  
作者: Diary    时间: 2018-10-10 20:35

佩服佩服啊.  
作者: 心仪    时间: 2018-10-26 16:22

支持一下  
作者: 剑啸寒    时间: 2018-10-28 16:39

不错,看看。  
作者: 锦锦乐道    时间: 2018-11-7 02:44

心脏干细胞




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