AJP - Renal Fuel your research with LabChart
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Am J Physiol Renal Physiol 287: F152-F159, 2004. First published March 9, 2004; doi:10.1152/ajprenal.00287.2003
0363-6127/04 $5.00
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
287/1/F152    most recent
00287.2003v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (19)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Paliege, A.
Right arrow Articles by Yang, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Paliege, A.
Right arrow Articles by Yang, T.

Inhibition of nNOS expression in the macula densa by COX-2-derived prostaglandin E2

Alex Paliege,1 Diane Mizel,1 Carmen Medina,2 Anita Pasumarthy,1 Yuning G. Huang,1 Sebastian Bachmann,3 Josephine P. Briggs,1 Jurgen B. Schnermann,1 and Tianxin Yang1,2

1National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; 3Department of Anatomy, University of Berlin, 13353 Berlin, Germany; and 2Division of Nephrology, University of Utah and Salt Lake Veterans Affairs Medical Center, Salt Lake City, Utah 84148

Submitted 18 August 2003 ; accepted in final form 13 February 2004


   ABSTRACT
TOP
 ABSTRACT
METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
It is well established that cyclooxygenase-2 (COX-2) and the neuronal form of nitric oxide synthase (nNOS) are coexpressed in macula densa cells and that the expression of both enzymes is stimulated in a number of high-renin states. To further explore the role of nNOS and COX-2 in renin secretion, we determined plasma renin activity in mice deficient in nNOS or COX-2. Plasma renin activity was significantly reduced in nNOS –/– mice on a mixed genetic background and in COX-2 –/– mice on either BALB/c or C57/BL6 congenic backgrounds. In additional studies, we accumulated evidence to show an inhibitory influence of PGE2 on nNOS expression. In a cultured macula densa cell line, PGE2 significantly reduced nNOS mRNA expression, as quantified by real-time RT-PCR. In COX-2 –/– mice, nNOS mRNA expression in the kidney, determined by real-time RT-PCR, was upregulated throughout the postnatal periods, ranging from postnatal day (PND) 3 to PND 60. The induction of nNOS protein expression and NOS activity in COX-2 –/– mice was localized to macula densa cells using immunohistochemistry and NADPH-diaphorase staining methods, respectively. Therefore, these findings reveal that the absence of either COX-2 or nNOS is associated with suppressed renin secretion. Furthermore, the inhibitory effect of PGE2 on nNOS mRNA expression indicates a novel interaction between NO and prostaglandin-mediated pathways of renin regulation.

juxtaglomerular apparatus; cyclooxygenase-2; neuronal nitric oxide synthase; real-time reverse transcriptase-polymerase chain reaction; plasma renin activity

ELUCIDATION OF THE pathways that determine renin secretion is of critical significance in understanding the role of the renin-angiotensin system in the control of extracellular volume and blood pressure. Macula densa (MD) control of renin secretion is one of the key mechanisms in the regulation of the renin-angiotensin system. The MD cells are unique cells in the kidney capable of sensing luminal NaCl concentrations and thereby regulating renin secretion rate as well as afferent arteriolar tone. Despite intensive investigation, the molecular mechanisms underlying the sensing function of the MD and its communication with vascular effector cells are still incompletely understood. There is consensus that activation of Na-K-2Cl cotransporter (NKCC2) activity in the apical membrane of the MD cells by high luminal NaCl initiates a chain of intra- and extracellular signals that lead to an inhibition of the release of renin secretion from granular cells. A large body of evidence suggests that prostaglandins (PGs) and nitric oxide (NO) may be part of this mediator chain.

Cyclooxygenase-2 (COX-2), the so-called inducible form of cyclooxygenase, is constitutively expressed in the MD and in adjacent cortical thick ascending limb (cTAL) cells (9, 20, 42). Its expression increases in various high-renin states including salt restriction, NKCC2 inhibition, unilateral renal artery stenosis, or blockade of the renin-angiotensin system (19). Participation of COX-2-generated PGs in the stimulation of the renin-angiotensin system under these circumstances is suggested by the inhibitory effects of COX-2 inhibitors reported by some laboratories (11, 18, 46). However, evidence to the contrary has also been reported so that a mandatory coupling between a COX-2 product and renin secretion is not universally accepted (24).

The neuronal form of nitric oxide synthase (nNOS) is abundantly expressed in MD cells (6, 26, 33, 47), and its expression is stimulated in various high-renin states including salt restriction (6, 41, 43), administration of loop diuretics (6), or inhibition of the renin-angiotensin system (27), some of the same interventions that augment COX-2 expression. Direct evidence in support of MD NOS, presumably nNOS, acting as a positive regulator of renin secretion came from studies in the in vitro perfused juxtaglomerular apparatus (JGA). In this preparation, administration of L-arginine-stimulated renin secretion and NOS blockers almost completely abolished the stimulation of renin secretion by low NaCl (21). Results from studies in which NOS inhibitors were administered to whole animals are somewhat less consistent; however, possibly because of the complexities that arise due to the multiple NOS isoforms and cellular sources (23, 40).

The first purpose of the present studies was to further investigate the roles of nNOS and COX-2 in control of renin secretion using nNOS and COX-2 knockout mice. If NO and PGs are important regulators of renin secretion, plasma renin levels should be markedly affected by the absence of either nNOS or COX-2. A second aim of these studies was to extend knowledge of interactions between nNOS and COX-2 and their bioactive products. Numerous studies have documented that NO can stimulate COX-2 activity in a number of different cell types, an effect that may play a role in the upregulation of COX-2 in inflammatory processes (38). In contrast, it is unclear whether PGs generated by COX-2 affect expression and activity of nNOS. The results of the present study demonstrate that plasma renin levels are significantly reduced in both nNOS and COX-2 knockout mice and that PGE2 exerts an inhibitory effect on nNOS expression in the MD. These results suggest a novel cross talk between COX-2 and nNOS that may play a critical role in stabilizing renin secretion.


   METHODS
TOP
 ABSTRACT
 METHODS
RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Materials. Cell culture media and serum were from Life Technologies (Gaithersburg, MD). PGE2 was from Cayman Chemical (Ann Arbor, MI). Rat nNOS antibody that cross-reacts with mouse nNOS was from Santa Cruz Biotechnology (Santa Cruz, CA). Primers and fluorescent probes for real-time PCR were synthesized by the Sequencing Core Facility at National Institute of Diabetes and Digestive and Kidney Diseases, and the probes were HPLC purified by Bioserv Biotechnologies (Laurel, MD). Other reagents for real-time PCR were from PE Applied Biosystems (Foster City, CA).

Animals. nNOS knockout mice on a mixed 129-C57/BL6 background used in the present study were originally generated by Huang et al. (22). The National Institutes of Health subcolony was derived from a heterozygous breeder pair supplied by Dr. O. Carretero (Henry Ford Hospital, Detroit, MI). Animals of the three genotypes were obtained by brother/sister mating of heterozygous offspring. COX-2 knockout mice on 129-C57/BL6 background were originally generated by Dinchuk et al. (13), and the breeder pairs were obtained from Jackson Laboratories.

Establishment of COX-2 congenic lines. Inbred C57/BL6 and BALB/c mice (Jackson Laboratories) were used to generate COX-2 knockout animals on C57/BL6 and BALB/c congenic backgrounds. According to conventional backcross breeding strategy (7, 25), male heterozygous COX-2 knockout mice were crossed with females of the inbred recipient strains, and this breeding strategy was repeated over 3 yr for multiple generations of backcrossing, N9 for BALB/c and N10 for C57/BL6. Congenic homozygous mice were obtained by brother/sister mating of heterozygous animals of the N9 and N10 generation, respectively.

Genotyping. Genomic DNA was isolated from a short segment of tail taken at the time of weaning. Genotyping was determined by PCR with nNOS or COX-2 gene-specific primers positioned in the targeted region and with Neor-specific primers. The sequence of the oligonucleotide primers and their location in the public sequence are as follows: nNOS sense 5'-CCAACCCAACGTCATTTCTG-3' (bp 131–150), antisense 5'-CATAGCTGAGGTCTACCAGG-3' (8); COX-2 sense 5'-GCAGCCAGTTGTCAAACTGC-3' (bp 961–980), COX-2 antisense 5'-CTCGGAAGAGCATCGCAGAGG-3' (bp 1081–1112) (15); Neor sense 5'-CTTGGGTGGAGAGGCTATTC-3' (bp 191–210), Neor antisense 5'-AGGTGAGATGACAGGAGATC-3' (bp 451–470) (2). Amplification was carried out for 30 cycles of 94°C for 40 s, 58°C for 40 s, and 72°C for 40 s, followed by a final extension at 72°C for 8 min.

Plasma renin concentration. Mice were anesthetized by an intraperitoneal injection of ketamine/xylazine (60 mg/kg). Blood was drawn from the vena cava using an insulin syringe coated with EDTA. Plasma renin concentration (PRC) was determined in the presence of excess rat angiotensinogen using a commercially available radioimmunoassay kit (PerkinElmer Life Sciences, Boston, MA) following instructions provided by the supplier.

Experimental protocols. Mouse macula densa-derived (MMDD1) cells, characterized in a previous study (50), were grown to confluence in six-well plates in DMEM supplemented with 10% fetal calf serum and antibiotics. To study the effect of PGE2 and forskolin on nNOS mRNA expression, confluent MMDD1 cells were treated with PGE2 or forskolin at appropriate concentrations. nNOS mRNA was determined by real-time RT-PCR.

cAMP enzyme immunoassay. Confluent MMDD1 cells were treated with PGE2 or vehicle in the presence of 10 µM IBMX in all groups. IBMX was used to prevent degradation of cAMP. cAMP content was determined by enzyme immunoassay following instructions from the supplier (Cayman Chemical). Acetylation was performed to enhance sensitivity of the assay.

Real-time RT-PCR. Total RNA was isolated from cells or renal tissues using TRIzol. One microgram of total RNA was denatured at 65°C for 5 min, and cDNA synthesis was then performed at 42°C for 1 h using Superscript reverse transcriptase (BRL, Gaithersburg, MD). For real-time PCR, oligonucleotides were chosen by using Primer Express 1.0 (PE Applied Biosystems) with probes being positioned at an exon-intron junction. Sequences of oligonucleotides are nNOS sense, 5'-GGGAAACTCTCGGAGGAGGA', antisense, 5'-TGAGG-GTGACCCCAAAGATG-3', and probe, 5'-(FAM)-CGTGGTACCGGTTGTCATCCCCTCAG-(TAMRA)-3'; COX-2 sense, 5'-CCCTGA-AGCCGTACACATCA-3', antisense, 5'-TGTCACTGTAGAGGGCT-TTCAATT-3', probe, 5'-(FAM)-TGCAGCCATTTCCTTCTCTCCTGTAAGTTCT-(TAMARA). Real-time PCR amplification was performed using TaqMan Universal PCR Master Mix and the ABI Prism 7900 Sequence Detection System (Applied Biosystems). Cycling conditions were 50°C for 2 min, 95°C for 10 min, followed by 40 repeats of 95°C for 0.15 min and 60°C for 1 min. Relative amounts of mRNA, normalized by {beta}-actin, were calculated from threshold cycle numbers (CT), i.e., 2–{Delta}{Delta}CT, according to the manufacturer's suggestion.

Immunohistochemistry. Kidneys were perfusion-fixed with 3% paraformaldehyde through an aortic cannula and processed for frozen sectioning. Five-micrometer cryostat sections were incubated in 0.5% Triton X-100/PBS for 30 min. After being rinsed in PBS, unspecific protein binding sites were blocked by a 2-h incubation with 5% dry milk. The primary antibody (rabbit anti-nNOS, Santa Cruz Biotechnology) was applied in a 1:50 dilution in 5% dry milk overnight at room temperature. After being rinsed in PBS, signals were detected with a Cy2-labeled secondary antibody and viewed in an Olympus IMT-2 microscope with a fluorescence module.

NADPH-diaphorase activity assay. This assay was performed as previously described (5). Briefly, 5-µm-thick cryostat sections were incubated in 0.1 mol/l phosphate buffer containing nitroblue tetrazolium (NBT), {beta}-NADPH, and Triton X-100 at 37°C. The reaction was stopped when the MD signal was clearly distinguishable and background staining had not yet appeared.

Statistical analysis. Values shown represent means ± SE. Statistical analysis was performed by ANOVA and Bonferroni tests with a P value of <0.05 being considered statistically significant.


   RESULTS
TOP
 ABSTRACT
 METHODS
 RESULTS
DISCUSSION
 GRANTS
 REFERENCES
 
Plasma renin in nNOS and COX-2 knockout mice. PRC was determined in nNOS –/– mice on a mixed genetic background [nNOS knockout (KO)], in two congenic strains of COX-2 –/– mice on BALB/c (COX-2 KO-BALB/c) and C57/BL6 (COX-2 KO-C57/BL6) backgrounds, and their respective wild-type control mice fed a normal-salt diet. The ages of these mice ranged from 2.5 to 3.5 mo. PRC averaged 222.3 ± 66.5 ng ANG I·ml–1·h–1 in wild-type mice, whereas a mean value of 31.9 ± 8 ng ANG I·ml–1·h–1 was found in nNOS –/– mice (P = 0.027). In wild-type BALB/c mice, PRC was 1,600 ± 447 ng ANG I·ml–1·h–1, whereas in COX-2 KO-BALB/c it averaged 131.7 ± 64 ng ANG I·ml–1·h–1 (P = 0.017). Corresponding values in wild-type C57/BL6 and COX-2 KO-C57/BL6 were 1,505 ± 475 and 320.2 ± 126 ng ANG I·ml–1·h–1 (P = 0.042). Differences in baseline values of PRC between the NOS and COX-2 series are most likely due to different housing conditions, with NOS mice housed in individual cages and COX-2 mice housed as a group. It seems likely that psychosocial stress levels were higher in the COX-2 mice caged as a group and that this contributed to the higher levels of PRC. Despite these differences in baseline values, the difference between the genotypes was comparable with PRC in the nNOS –/–, being 80.7% lower than in wild-type control mice (Fig. 1A), while COX-2 KO-BALB/c and COX-2 KO-C57/BL6 (Fig. 1B) mice had a 91.8 and 78.7% reduction in PRC, respectively.



View larger version (12K):
[in this window]
[in a new window]
  		Fig. 1. Plasma renin concentration (PRC) in neuronal nitric oxide synthase (nNOS) –/– mice on a mixed genetic background (A) and cyclooxygenase-2 (COX-2) –/– mice on congenic BALB/c and C57/BL6 backgrounds (B). PRC was determined by radioimmunoassay and expressed as ng ANG I·ml–1·h–1. Values are means ± SE.

 
Effect of PGE2 on nNOS mRNA expression in cultured MD cells. We examined whether the administration of exogenous PGE2 has an effect on nNOS expression in cultured MMDD1 cells (50). Confluent MMDD1 cells were treated for 16 h with PGE2 or vehicle, and nNOS mRNA was quantified by real-time RT-PCR. A fluorescent probe was positioned at an exon-intron junction, allowing specific detection of mRNA, but not genomic DNA, as confirmed by the absence of signals from RT minus controls (data not shown). Parallel real-time RT-PCR for {beta}-actin was performed to normalize for variations in cDNA concentration. PGE2 at 1 and 5 µM consistently reduced nNOS mRNA expression in a dose-dependent manner (Fig. 2).



View larger version (10K):
[in this window]
[in a new window]
  		Fig. 2. Effect of PGE2 on nNOS mRNA expression in mouse macula densa-derived (MMDD1) cells. Confluent MMDD1 cells were treated for 16 h with PGE2 at the indicated concentrations. nNOS and {beta}-actin mRNA expressions were determined by real-time RT-PCR. Relative abundance of nNOS mRNA, normalized by {beta}-actin, was calculated from threshold cycles (CT), i.e., 2–{Delta}{Delta}CT. Values are means ± SE.

 
To address the signaling mechanism responsible for the PGE2 effect in MMDD1 cells, we first examined whether PGE2 exerts its inhibitory effect on nNOS expression through cAMP. Confluent MMDD1 cells were treated for 30 min with 5 µM PGE2 in the presence of 10 µM IBMX to prevent degradation of cAMP. Forskolin served as a positive control for the assay. cAMP content was determined by enzyme immunoassay using acetylation to enhance the sensitivity of the assay. As shown in Fig. 3, PGE2 induced a significant increase in cAMP content, as did forskolin, a strong activator of adenyl cyclase. Similar to PGE2, forskolin was found to significantly suppress nNOS mRNA expression (Fig. 4).



View larger version (15K):
[in this window]
[in a new window]
  		Fig. 3. Effect of PGE2 on cAMP content in cultured MMDD1 cells. Confluent MMDD1 cells were treated for 30 min with PGE2, forskolin, or vehicle in the presence of 10 µM IBMX in all groups. The supernatant of cell lysates was acetylated and cAMP content was determined by enzyme immunoassay. Values are means ± SE.

 


View larger version (13K):
[in this window]
[in a new window]
  		Fig. 4. Effect of forskolin on nNOS mRNA expression in cultured MMDD1 cells. Confluent MMDD1 cells were treated for 16 h with forskolin at the indicated concentration. Quantification of nNOS mRNA was performed as described in Fig. 2.

 
nNOS expression in the MD of COX-2 knockout mice. To further pursue the notion that PGE2 inhibits nNOS expression, we examined nNOS expression in the MD of COX-2 knockout mice using the 129/C57 mixed background strain. To minimize the possibility that changes in nNOS expression might be secondary to the morphological changes that develop in COX-2-deficient animals with time, experiments were performed in mice at early postnatal periods as well as in adults. nNOS mRNA in the kidney was determined by real-time RT-PCR. An induction of nNOS mRNA in the whole kidney of COX-2 –/– mice was consistently observed on postnatal day 3 (PND 3; Fig. 5A) and PND 10 (Fig. 5B). In adult mice (PND 60), a significant induction of COX-2 expression mRNA in COX-2 –/– mice was detected only in the renal cortex but not in the outer or inner medulla (Fig. 5C). Using immunohistochemistry and NADPH-diaphorase staining, the increase in both nNOS protein expression (Fig. 6) and NADPH-diaphorase activity (Fig. 7) of adult COX-2 –/– mice was localized to the MD.



View larger version (11K):
[in this window]
[in a new window]
  		Fig. 5. Real-time RT-PCR quantification of nNOS mRNA expression in the kidney of COX-2 –/– mice and age-matched controls at various developmental periods. Whole kidneys in young mice at postnatal day 3 (PND 3; n = 8 in each –/– and +/+ group) and PND 10 (n = 4) and kidney regions (CO, cortex; OM, outer medulla; IM, inner medulla) in adult mice at PND 60 (n = 4) were dissected and subject to RNA extraction and real-time RT-PCR for nNOS and {beta}-actin. Shown is the relative abundance of nNOS mRNA normalized by {beta}-actin.

 


View larger version (59K):
[in this window]
[in a new window]
  		Fig. 6. Upregulation of nNOS protein in the macula densa of adult COX-2 homozygous mice. A: representative views of immunostaining of nNOS in the macula densa of COX-2 –/– mice and age-matched controls. B: numbers of nNOS-immunoreactive macula densa cells expressed as positive cells/glomerulus.

 


View larger version (97K):
[in this window]
[in a new window]
  		Fig. 7. Upregulation of NOS activity in the macula densa of adult COX-2 homozygous mice. The in situ NOS activity was determined by NADPH-diaphorase assay. A: representative views of NOS activities in the macula densa of COX-2 –/– mice and age-matched controls. B: numbers of positive macula densa cells expressed as positive cells/glomerulus.

 
Renal COX-2 expression in nNOS knockout mice. Considering that NO is a potential regulator of COX-2 expression, we determined whether renal cortical COX-2 expression is altered in nNOS –/– mice using real-time RT-PCR. As shown in Fig. 8, there was no decrease but a slight increase of COX-2 mRNA in the renal cortex of nNOS –/– mice compared with wild-type controls. However, this increase of COX-2 mRNA did not reach statistical significance.



View larger version (8K):
[in this window]
[in a new window]
  		Fig. 8. Real-time RT-PCR quantification of COX-2 mRNA expression in the renal cortex of nNOS –/– mice and age-matched controls. Renal cortex was dissected and subject to RNA extraction and real-time RT-PCR for COX-2 and {beta}-actin. Shown is relative abundance of COX-2 mRNA normalized by {beta}-actin.

 

   DISCUSSION
TOP
 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
GRANTS
 REFERENCES
 
In addition to being the likely receptor cells for the tubuloglomerular feedback response, MD cells act as sensor cells in the tubular control of renin secretion, one of the major physiological mechanisms in the control of plasma renin levels. Motivated by the observations that both nNOS and COX-2 are constitutively expressed in MD cells, substantial experimental effort has been devoted to elucidating the roles of NO and PGs in the renin-secretory response to changes in luminal NaCl concentration. A sizable body of evidence now suggests that both PGs and NO are part of the mediating pathway for MD-dependent renin release and that several negative feedback pathways exist that stabilize renin secretion at a given level of MD input.

If in fact MD control of renin secretion is dependent on both local nNOS-dependent NO formation and on COX-2-dependent PG synthesis, one would expect that the absence of either enzyme should have discernible effects on renin secretion. Thus, in the first part of this study, we determined PRC in nNOS or COX-2 knockout mice to address the question of the effect of a complete absence of either nNOS or COX-2 on renin secretion. Our data show that the level of plasma renin is significantly and approximately equally reduced in mice deficient in either nNOS or COX-2 enzymes compared with their wild-type controls.

Findings in nNOS knockout mice are consistent with earlier evidence in support of the notion that nNOS-generated NO exerts a tonic stimulatory effect on renin release. A special role of NO in the local regulation of renin secretion by the MD is suggested by the expression of nNOS in MD cells (6, 26, 33, 47). In addition, nNOS immunoreactivity in MD cells colocalizes with NOS activity as determined by NADPH-diaphorase activity using the NBT reaction (1). Glucose-6-phosphate dehydrogenase, a NADPH-generating enzyme, is more abundant in MD cells than in any other renal epithelial cells (34). Functional evidence for a link between nNOS in MD cells and renin secretion is provided by the observation that 7-nitroindazole attenuates furosemide-stimulated renin release, presumably predominantly a MD-mediated effect, but that it does not change the renin stimulation caused by a reduction in renal perfusion pressure (3, 4). When given chronically, 7-nitroindazole also prevented the stimulation of renin secretion resulting from a 7-day treatment with a low-salt diet (3). Furthermore, in an isolated JGA preparation in which nNOS in MD cells is probably the major enzyme responsible for regulated NO release, the stimulation of renin secretion by low NaCl was largely blocked by NOS inhibition (21). Despite a large number of studies supporting a tonically stimulatory role of NO in MD-dependent renin secretion, contradictory observations have also been reported. For example, in an isolated, perfused JGA preparation, elevation of luminal NaCl stimulates NO production measured by DAF-2 fluorescence (28, 31). This effect of NaCl may be most pronounced at concentrations greater than 60 mM, a range where renin secretion is maximally suppressed (21, 28). Thus it is conceivable that the rise in NO is responsible for the failure of high NaCl concentrations to further reduce renin secretion. There is also a limitation of the systemic gene knockout approach in addressing the MD nNOS function given the fact that in addition to the MD cells, nNOS is expressed in other cell types as well, such as renal medullary cells. Systemic factors unrelated to the MD may also be responsible for the reduction of renin in nNOS knockout mice. For example, it has been shown that chronic nNOS inhibition with 7-nitroindazole causes an increase in arterial blood pressure, indicating that nNOS deficiency may cause salt retention and extracellular volume expansion (35).

Evidence for a specific role of PGs in MD control of renin secretion has existed even before it was clear that COX-2 was present in the MD, with experimental observations supporting an involvement of PGs in the release of renin initiated by the MD input but not in baroreceptor-mediated renin secretion (16). The current results showing a significant reduction of plasma renin in COX-2-deficient mice are consistent with a COX-2-generated PG being involved in the control of renin secretion. Our observations confirm an earlier study in which an ~50% reduction in plasma renin activity was noted in COX-2 knockout mice on a mixed genetic background (12). The present studies were performed in mice in which the COX-2 deletion had been bred into congenic C57/BL6 and BALB/c backgrounds using backcrossing of the original knockout mice for 9 or 10 generations. Because plasma renin levels were reduced in both congenic strains compared with their wild-type controls, it appears that differences in genetic background cannot account for the renin phenotype in these mice. These observations complement earlier studies showing that renin mRNA expression and the renin response to salt depletion were reduced in COX-2 knockout mice on a mixed genetic background (49). COX-2 inhibitors also reduce plasma renin activity in patients with Bartter's syndrome and significantly ameliorate the polyuria and elevated sodium excretion caused by NKCC2 malfunction (37). Using an in vitro perfused preparation of the JGA, Traynor et al. (44) demonstrated that NS-398 completely abolished low-NaCl-stimulated renin secretion. Recent elegant experiments in a similar JGA preparation have shown that lowering luminal NaCl concentration causes the release of PGE2 from MD cells (36).

Similar to most systems involved in body homeostasis, renin secretion is under the control of several negative feedback inputs that stabilize renin secretion in the face of stimulatory or feedforward effects. For example, it has long been recognized that ANG II itself inhibits renin release (17). Furthermore, more recent studies indicate that ANG II inhibits COX-2 activity and the secretion of renin-stimulatory PGs (11, 48). Finally, ANG II deficiency in angiotensinogen knockout mice is associated with an increase in MD nNOS expression, suggesting that ANG II also downregulates nNOS (26). In the second part of the present study, we report experimental evidence suggesting another negative feedback loop in which PGE2 generated by COX-2 exerts an inhibitory influence on MD nNOS expression. Using a quantitative real-time RT-PCR method, we consistently observed that PGE2 downregulates nNOS mRNA expression in cultured MD cells in a dose-dependent manner. To our knowledge, this is the first report demonstrating PGE2 downregulation of nNOS in MD cells. The demonstration of dynamic changes in gene expression of the so-called "constitutive" nNOS makes this cell culture model a useful tool to further characterize transcription or posttranscriptional mechanisms governing nNOS gene expression. This in vitro finding is in full agreement with the observation that the MD expression of nNOS was upregulated in COX-2 knockout mice as demonstrated both at the mRNA and protein levels. Using real-time RT-PCR, we quantified nNOS mRNA in the kidney of COX-2 knockout mice at various developmental periods. An induction of nNOS mRNA in the kidney of COX-2 –/– mice was consistently observed at early postnatal periods before the development of the obvious renal abnormalities seen in COX-2 knockout mice with aging. In adult 2-mo-old COX-2 –/– mice, the induction of nNOS mRNA was found to be restricted to the cortex and was not seen in the outer or inner medulla, consistent with the MD localization of nNOS. We previously found that the glomerular filtration rate (GFR) in male COX-2 –/– mice remained normal until 2 mo of age and started to decline afterward, whereas a fall in GFR in female COX-2 –/– mice was not demonstrable over a 1-yr period (data not shown). Therefore, it is unlikely that the induction of nNOS in the kidney of COX-2 –/– mice is secondary to any morphological or functional abnormalities. Using immunohistochemistry and NADPH-diaphorase staining, we confirmed the induction of nNOS in MD cells of COX-2 –/– mice at the protein and enzyme activity level. Based on the demonstration that PGE2 inhibits nNOS mRNA expression in cultured MD cells, we assume that reduced production and release of PGE2 by MD cells of COX-2 knockout mice are the causes of the stimulation of nNOS expression. However, reduced ANG II feedback inhibition resulting from the decrease in plasma renin may contribute to the increase in MD nNOS in COX-2 knockout mice (26).

It is noteworthy that there is no reduction in COX-2 expression in the renal cortex of nNOS –/– mice. Literature concerning dependence of the MD/cTAL COX-2 on NO is conflicting. COX-2 immunoreactivity in the MD cells, determined by a semiquantitative immunohistochemistry technique, is not altered in nNOS –/– mice (42). In contrast, nNOS inhibition with 7-nitroindazole or S-methyl-thiocitrulline remarkably suppresses COX-2 expression in the MD/cTAL in Sprague-Dawley rats (10). The reason for this discrepancy is not known but is possibly related to the high complexity of NO system in the JGA. It is possible that the MD COX-2 expression is under the control of NO derived from multiple sources including nNOS and endothelial (e)NOS. Recent evidence suggests that eNOS may also play a role in the regulation of renin secretion as does nNOS. In this regard, eNOS expression in afferent arterioles is stimulated by salt restriction (43) and plasma renin activity is downregulated in eNOS knockout mice (45). Future studies need to determine the COX-2 expression in models with combined blockade of both nNOS and eNOS. Another possibility is that COX-2 and nNOS mediate parallel renin regulation pathways that interact in a unique way. It is known that NO can exert a direct stimulatory effect on renin secretion in cultured JG cells via elevation of cAMP resulting from cGMP-dependent inhibition of phosphodiesterase 3 (30).

To address the question of the signaling mechanism that may mediate the inhibition of nNOS expression by PGE2 in MD cells, we examined the possibility that PGE2 exerts its effect through the cAMP pathway. In fact, PGE2 was found to increase the accumulation of cAMP in cultured MD cells. This observation suggests that cAMP may be a negative regulator of nNOS expression, an assumption that is supported by the inhibitory effect of the direct activator of adenyl cyclase forskolin. There is an earlier study to indicate that phosphorylation of purified nNOS by protein kinase A and other kinases also causes a marked reduction in nNOS activity within the timespan of an hour (14). Inhibition of nNOS expression in MD cells through the cAMP pathway is opposite to the stimulatory effect of cAMP on the transcription and activity of inducible NOS observed in a number of different cells (29, 39). Thus the regulatory role of protein kinase A appears to be different between Ca2+-dependent and Ca2+-independent forms of NOS. It is unclear which PGE2 EP receptor may mediate the inhibitory effect of PGE2 on nNOS expression, but EP2 or EP4 are likely candidates because they couple to Gs and increase cAMP. Nevertheless, an immunohistochemical study was unable to detect any of the four EP receptors in the MD (32). This may be related to the limitations of the techniques such as low sensitivity, high background, or poor resolution. The issue needs to be addressed in future studies using different approaches such as laser capture microdissection coupled with real-time RT-PCR techniques.

In summary, a reduction in plasma renin activity in both nNOS- and COX-2-deficient mice suggests a tonic stimulatory role of NO and PGs in renin secretion. Whether NO and PGs act in concert or independently remains to be determined. Furthermore, upregulation of nNOS expression in COX-2 knockout mice and inhibition of nNOS expression in cultured MD cells by PGE2 suggest an inhibitory influence of COX-2-generated PGE2 on nNOS-dependent NO formation.


   GRANTS
TOP
 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
 GRANTS
REFERENCES
 
The work was supported by intramural funds from National Institute of Diabetes and Digestive and Kidney Diseases, start-up funds from the Department of Internal Medicine at University of Utah, NIH Grants DK-064981 and DK-066592 (to T. Yang), and American Heart Association Grant 0335305N (to T. Yang).


   ACKNOWLEDGMENTS
 
We thank Dr. C. Noguchi at National Institutes of Health (NIH) for assistance in performing real-time PCR.


   FOOTNOTES
 

Address for reprint requests and other correspondence: T. Yang, Univ. of Utah and Veterans Affairs Medical Center, Bldg 2, Research Service (151 E), 500 Foothill Drive, Salt Lake City, UT 84148 (E-mail: tianxin.yang{at}hsc.utah.edu).

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.


   REFERENCES
TOP
 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 

  1. Bachmann S, Bosse HM, and Mundel P. Topography of nitric oxide synthesis by localizing constitutive NO synthases in mammalian kidney. Am J Physiol Renal Fluid Electrolyte Physiol 268: F885–F898, 1995.[Abstract/Free Full Text]
  2. Beck E, Ludwig G, Auerswald EA, Reiss B, and Schaller H. Nucleotide sequence and exact localization of the neomycin phosphotransferase gene from transposon Tn5. Gene 19: 327–336, 1982.[CrossRef][ISI][Medline]
  3. Beierwaltes WH. Macula densa stimulation of renin is reversed by selective inhibition of neuronal nitric oxide synthase. Am J Physiol Regul Integr Comp Physiol 272: R1359–R1364, 1997.[Abstract/Free Full Text]
  4. Beierwaltes WH. Selective neuronal nitric oxide synthase inhibition blocks furosemide-stimulated renin secretion in vivo. Am J Physiol Renal Fluid Electrolyte Physiol 269: F134–F139, 1995.[Abstract/Free Full Text]
  5. Bosse HM and Bachmann S. Immunohistochemically detected protein nitration indicates sites of renal nitric oxide release in Goldblatt hypertension. Hypertension 30: 948–952, 1997.[Abstract/Free Full Text]
  6. Bosse HM, Bohm R, Resch S, and Bachmann S. Parallel regulation of constitutive NO synthase and renin at JGA of rat kidney under various stimuli. Am J Physiol Renal Fluid Electrolyte Physiol 269: F793–F805, 1995.[Abstract/Free Full Text]
  7. Boyse EA. The increasing value of congenic mice in biomedical research. Lab Anim Sci 27: 771–781, 1977.[ISI][Medline]
  8. Brenman JE, Christopherson KS, Craven SE, McGee AW, and Bredt DS. Cloning and characterization of postsynaptic density 93, a nitric oxide synthase interacting protein. J Neurosci 16: 7407–7415, 1996.[Abstract/Free Full Text]
  9. Campean V, Theilig F, Paliege A, Breyer M, and Bachmann S. Key enzymes for renal prostaglandin synthesis: site-specific expression in rodent kidney (rat, mouse). Am J Physiol Renal Physiol 285: F19–F32, 2003.[Abstract/Free Full Text]
  10. Cheng HF, Wang JL, Zhang MZ, McKanna JA, and Harris RC. Nitric oxide regulates renal cortical cyclooxygenase-2 expression. Am J Physiol Renal Physiol 279: F122–F129, 2000.[Abstract/Free Full Text]
  11. Cheng HF, Wang JL, Zhang MZ, Miyazaki Y, Ichikawa I, McKanna JA, and Harris RC. Angiotensin II attenuates renal cortical cyclooxygenase-2 expression. J Clin Invest 103: 953–961, 1999.[ISI][Medline]
  12. Cheng HF, Wang JL, Zhang MZ, Wang SW, McKanna JA, and Harris RC. Genetic deletion of COX-2 prevents increased renin expression in response to ACE inhibition. Am J Physiol Renal Physiol 280: F449–F456, 2001.[Abstract/Free Full Text]
  13. Dinchuk JE, Car BD, Focht RJ, Johnston JJ, Jaffee BD, Covington MB, Contel NR, Eng VM, Collins RJ, Czerniak PM, Gorry SA, and Trzaskos JM. Renal abnormalities and an altered inflammatory response in mice lacking cyclooxygenase II. Nature 378: 406–409, 1995.[CrossRef][Medline]
  14. Dinerman JL, Steiner JP, Dawson TM, Dawson V, and Snyder SH. Cyclic nucleotide dependent phosphorylation of neuronal nitric oxide synthase inhibits catalytic activity. Neuropharmacology 33: 1245–1251, 1994.[CrossRef][ISI][Medline]
  15. Fletcher BS, Kujubu DA, Perrin DM, and Herschman HR. Structure of the mitogen-inducible TIS10 gene and demonstration that the TIS10-encoded protein is a functional prostaglandin G/H synthase. J Biol Chem 267: 4338–4344, 1992.[Abstract/Free Full Text]
  16. Gerber JG, Nies AS, and Olsen RD. Control of canine renin release: macula densa requires prostaglandin synthesis. J Physiol 319: 419–429, 1981.[Abstract/Free Full Text]
  17. Hackenthal E, Paul M, Ganten D, and Taugner R. Morphology, physiology, and molecular biology of renin secretion. Physiol Rev 70: 1067–1116, 1990.[Free Full Text]
  18. Harding P, Sigmon DH, Alfie ME, Huang PL, Fishman MC, Beierwaltes WH, and Carretero OA. Cyclooxygenase-2 mediates increased renal renin content induced by low sodium diet. Hypertension 29: 297–302, 1997.[Abstract/Free Full Text]
  19. Harris RC and Breyer MD. Physiological regulation of cyclooxygenase-2 in the kidney. Am J Physiol Renal Physiol 281: F1–F11, 2001.[Abstract/Free Full Text]
  20. Harris RC, McKanna JA, Akai Y, Jacobson HR, Dubois RN, and Breyer MD. Cyclooxygenase-2 is associated with the macula densa of rat kidney and increases with salt restriction. J Clin Invest 94: 2504–2510, 1994.[ISI][Medline]
  21. He XR, Greenberg SG, Briggs JP, and Schnermann JB. Effect of nitric oxide on renin secretion. II. Studies in the perfused juxtaglomerular apparatus. Am J Physiol Renal Fluid Electrolyte Physiol 268: F953–F959, 1995.[Abstract/Free Full Text]
  22. Huang PL, Dawson TM, Bredt DS, Snyder SH, and Fishman MC. Targeted disruption of the neuronal nitric oxide synthase gene. Cell 75: 1273–1286, 1993.[CrossRef][ISI][Medline]
  23. Johnson RA and Freeman RH. Renin release in rats during blockade of nitric oxide synthesis. Am J Physiol Regul Integr Comp Physiol 266: R1723–R1729, 1994.[Abstract/Free Full Text]
  24. Kammerl MC, Nusing RM, Seyberth HW, Riegger GA, Kurtz A, and Kramer BK. Inhibition of cyclooxygenase-2 attenuates urinary prostanoid excretion without affecting renal renin expression. Pflügers Arch 442: 842–847, 2001.[CrossRef][ISI][Medline]
  25. Kent G, Iles R, Bear CE, Huan LJ, Griesenbach U, McKerlie C, Frndova H, Ackerley C, Gosselin D, Radzioch D, O'Brodovich H, Tsui LC, Buchwald M, and Tanswell AK. Lung disease in mice with cystic fibrosis. J Clin Invest 100: 3060–3069, 1997.[ISI][Medline]
  26. Kihara M, Umemura S, Kadota T, Yabana M, Tamura K, Nyuui N, Ogawa N, Murakami K, Fukamizu A, and Ishii M. The neuronal isoform of constitutive nitric oxide synthase is upregulated in the macula densa of angiotensinogen gene-knockout mice. Lab Invest 76: 285–294, 1997.[ISI][Medline]
  27. Kihara M, Umemura S, Sugaya T, Toya Y, Yabana M, Kobayashi S, Tamura K, Kadota T, Kishida R, Murakami K, Fukamizu A, and Ishii M. Expression of neuronal type nitric oxide synthase and renin in the juxtaglomerular apparatus of angiotensin type-1a receptor gene-knockout mice. Kidney Int 53: 1585–1593, 1998.[CrossRef][ISI][Medline]
  28. Kovacs G, Komlosi P, Fuson A, Peti-Peterdi J, Rosivall L, and Bell PD. Neuronal nitric oxide synthase: its role and regulation in macula densa cells. J Am Soc Nephrol 14: 2475–2483, 2003.[Abstract/Free Full Text]
  29. Kunz D, Muhl H, Walker G, and Pfeilschifter J. Two distinct signaling pathways trigger the expression of inducible nitric oxide synthase in rat renal mesangial cells. Proc Natl Acad Sci USA 91: 5387–5391, 1994.[Abstract/Free Full Text]
  30. Kurtz A, Gotz KH, Hamann M, and Wagner C. Stimulation of renin secretion by nitric oxide is mediated by phosphodiesterase 3. Proc Natl Acad Sci USA 95: 4743–4747, 1998.[Abstract/Free Full Text]
  31. Liu R, Pittner J, and Persson AE. Changes of cell volume and nitric oxide concentration in macula densa cells caused by changes in luminal NaCl concentration. J Am Soc Nephrol 13: 2688–2696, 2002.[Abstract/Free Full Text]
  32. Morath R, Klein T, Seyberth HW, and Nusing RM. Immunolocalization of the four prostaglandin E2 receptor proteins EP1, EP2, EP3, and EP4 in human kidney. J Am Soc Nephrol 10: 1851–1860, 1999.[Abstract/Free Full Text]
  33. Mundel P, Bachmann S, Bader M, Fischer A, Kummer W, Mayer B, and Kriz W. Expression of nitric oxide synthase in kidney macula densa cells. Kidney Int 42: 1017–1019, 1992.[ISI][Medline]
  34. Norgaard T. Quantitative measurement of glucose-6-phosphate dehydrogenase in cortical fractions of the rabbit nephron. Histochemistry 63: 103–113, 1979.[CrossRef][ISI][Medline]
  35. Ollerstam A, Pittner J, Persson AE, and Thorup C. Increased blood pressure in rats after long-term inhibition of the neuronal isoform of nitric oxide synthase. J Clin Invest 99: 2212–2218, 1997.[ISI][Medline]
  36. Peti-Peterdi J, Komlosi P, Fuson AL, Guan Y, Schneider A, Qi Z, Redha R, Rosivall L, Breyer MD, and Bell PD. Luminal NaCl delivery regulates basolateral PGE2 release from macula densa cells. J Clin Invest 112: 76–82, 2003.[CrossRef][ISI][Medline]
  37. Reinalter SC, Jeck N, Brochhausen C, Watzer B, Nusing RM, Seyberth HW, and Komhoff M. Role of cyclooxygenase-2 in hyperprostaglandin E syndrome/antenatal Bartter syndrome. Kidney Int 62: 253–260, 2002.[CrossRef][ISI][Medline]
  38. Salvemini D, Misko TP, Masferrer JL, Seibert K, Currie MG, and Needleman P. Nitric oxide activates cyclooxygenase enzymes. Proc Natl Acad Sci USA 90: 7240–7244, 1993.[Abstract/Free Full Text]
  39. Schini-Kerth VB, Fisslthaler B, and Busse R. CGRP enhances induction of NO synthase in vascular smooth muscle cells via a cAMP-dependent mechanism. Am J Physiol Heart Circ Physiol 267: H2483–H2490, 1994.[Abstract/Free Full Text]
  40. Sigmon DH, Carretero OA, and Beierwaltes WH. Endothelium-derived relaxing factor regulates renin release in vivo. Am J Physiol Renal Fluid Electrolyte Physiol 263: F256–F261, 1992.[Abstract/Free Full Text]
  41. Singh I, Grams M, Wang WH, Yang T, Killen P, Smart A, Schnermann J, and Briggs JP. Coordinate regulation of renal expression of nitric oxide synthase, renin, and angiotensinogen mRNA by dietary salt. Am J Physiol Renal Fluid Electrolyte Physiol 270: F1027–F1037, 1996.[Abstract/Free Full Text]
  42. Theilig F, Campean V, Paliege A, Breyer M, Briggs JP, Schnermann J, and Bachmann S. Epithelial COX-2 expression is not regulated by nitric oxide in rodent renal cortex. Hypertension 39: 848–853, 2002.[Abstract/Free Full Text]
  43. Tojo A, Kimoto M, and Wilcox CS. Renal expression of constitutive NOS and DDAH: separate effects of salt intake and angiotensin. Kidney Int 58: 2075–2083, 2000.[CrossRef][ISI][Medline]
  44. Traynor TR, Smart A, Briggs JP, and Schnermann J. Inhibition of macula densa-stimulated renin secretion by pharmacological blockade of cyclooxygenase-2. Am J Physiol Renal Physiol 277: F706–F710, 1999.[Abstract/Free Full Text]
  45. Wagner C, Godecke A, Ford M, Schnermann J, Schrader J, and Kurtz A. Regulation of renin gene expression in kidneys of eNOS- and nNOS- deficient mice. Pflügers Arch 439: 567–572, 2000.[CrossRef][ISI][Medline]
  46. Wang JL, Cheng HF, and Harris RC. Cyclooxygenase-2 inhibition decreases renin content and lowers blood pressure in a model of renovascular hypertension. Hypertension 34: 96–101, 1999.[Abstract/Free Full Text]
  47. Wilcox CS and Welch WJ. Macula densa nitric oxide synthase: expression, regulation, and function. Kidney Int Suppl 67: S53–S57, 1998.[Medline]
  48. Wolf K, Castrop H, Hartner A, Goppelt-Strube M, Hilgers KF, and Kurtz A. Inhibition of the renin-angiotensin system upregulates cyclooxygenase-2 expression in the macula densa. Hypertension 34: 503–507, 1999.[Abstract/Free Full Text]
  49. Yang T, Endo Y, Huang YG, Smart A, Briggs JP, and Schnermann J. Renin expression in COX-2-knockout mice on normal- or low-salt diets. Am J Physiol Renal Physiol 279: F819–F825, 2000.[Abstract/Free Full Text]
  50. Yang T, Park JM, Arend L, Huang Y, Topaloglu R, Pasumarthy A, Praetorius H, Spring K, Briggs JP, and Schnermann J. Low chloride stimulation of prostaglandin E2 release and cyclooxygenase-2 expression in a mouse macula densa cell line. J Biol Chem 275: 37922–37929, 2000.[Abstract/Free Full Text]



This article has been cited by other articles:


Home page
 Am. J. Physiol. Renal Physiol.Home page
T. Aoyagi, Y. Izumi, M. Hiroyama, T. Matsuzaki, Y. Yasuoka, A. Sanbe, H. Miyazaki, Y. Fujiwara, Y. Nakayama, Y. Kohda, et al.
Vasopressin regulates the renin-angiotensin-aldosterone system via V1a receptors in macula densa cells
Am J Physiol Renal Physiol, July 1, 2008; 295(1): F100 - F107.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
H. Liu, W. Ye, G. Guan, Z. Dong, Z. Jia, and T. Yang
Developmental regulation of calcineurin isoforms in the rodent kidney: association with COX-2
Am J Physiol Renal Physiol, December 1, 2007; 293(6): F1898 - F1904.
[Abstract] [Full Text] [PDF]

Home page
 Physiol. Rev.Home page
R. A. Fenton and M. A. Knepper
Mouse Models and the Urinary Concentrating Mechanism in the New Millennium
Physiol Rev, October 1, 2007; 87(4): 1083 - 1112.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
V. Bachteeva, E. Fock, E. Lavrova, S. Nikolaeva, S. Gambaryan, and R. Parnova
Prostaglandin E2 inhibits vasotocin-induced osmotic water permeability in the frog urinary bladder by EP1-receptor-mediated activation of NO/cGMP pathway
Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2007; 293(1): R528 - R537.
[Abstract] [Full Text] [PDF]

Home page
 Annals of Clinical & Laboratory ScienceHome page
G. Natarajan, M. Glibetic, V. Raykova, J. P Ofenstein, R. L Thomas, and J. V Aranda
Nitric Oxide and Prostaglandin Response to Group B Streptococcal Infection in the Lung
Ann. Clin. Lab. Sci., January 1, 2007; 37(2): 170 - 176.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
S. M. Kim, L. Chen, D. Mizel, Y. G. Huang, J. P. Briggs, and J. Schnermann
Low plasma renin and reduced renin secretory responses to acute stimuli in conscious COX-2-deficient mice
Am J Physiol Renal Physiol, January 1, 2007; 292(1): F415 - F422.
[Abstract] [Full Text] [PDF]

Home page
 Circ. Res.Home page
Z. Jia, A. Zhang, H. Zhang, Z. Dong, and T. Yang
Deletion of Microsomal Prostaglandin E Synthase-1 Increases Sensitivity to Salt Loading and Angiotensin II Infusion
Circ. Res., November 24, 2006; 99(11): 1243 - 1251.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
F. Theilig, H. Debiec, B. Nafz, P. Ronco, R. Nusing, H. W. Seyberth, H. Pavenstadt, N. Bouby, and S. Bachmann
Renal cortical regulation of COX-1 and functionally related products in early renovascular hypertension (rat)
Am J Physiol Renal Physiol, November 1, 2006; 291(5): F987 - F994.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
T. Yang, A. Zhang, A. Pasumarthy, L. Zhang, Z. Warnock, and J. B. Schnermann
Nitric oxide stimulates COX-2 expression in cultured collecting duct cells through MAP kinases and superoxide but not cGMP
Am J Physiol Renal Physiol, October 1, 2006; 291(4): F891 - F895.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
B. Yao, J. Xu, Z. Qi, R. C. Harris, and M.-Z. Zhang
Role of renal cortical cyclooxygenase-2 expression in hyperfiltration in rats with high-protein intake
Am J Physiol Renal Physiol, August 1, 2006; 291(2): F368 - F374.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
H.-F. Cheng, M.-Z. Zhang, and R. C. Harris
Nitric oxide stimulates cyclooxygenase-2 in cultured cTAL cells through a p38-dependent pathway
Am J Physiol Renal Physiol, June 1, 2006; 290(6): F1391 - F1397.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
W. Ye, H. Zhang, E. Hillas, D. E. Kohan, R. L. Miller, R. D. Nelson, M. Honeggar, and T. Yang
Expression and function of COX isoforms in renal medulla: evidence for regulation of salt sensitivity and blood pressure
Am J Physiol Renal Physiol, February 1, 2006; 290(2): F542 - F549.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
287/1/F152    most recent
00287.2003v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend