Renal expression of aminopeptidase A in rats with two-kidney, one-clip hypertension

Gunter Wolf, Ulrich Wenzel, Karel J. M. Assmann1 and Rolf A. K. Stahl

Department of Medicine, Division of Nephrology and Osteology, University of Hamburg, Hamburg, Germany and 1 Department of Pathology, University Hospital Nijmegen, Nijmegen, The Netherlands



   Abstract
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Background. Angiotensin II (ANG II) is a major factor involved in the progression of chronic renal disease. Although the generation of this vasoactive peptide has been investigated in great detail, only a few studies have hitherto addressed the metabolism of ANG II into fragments such as angiotensin III and IV (ANG III, IV) which may exert physiological effects independent of ANG II. Aminopeptidase A (APA) is the major enzyme degrading ANG II. The aim of the current study was to evaluate glomerular APA expression in rats with two-kidney, one-clip hypertension.

Methods. The left renal artery was restricted with a 0.2-mm silver clip. Kidneys were harvested 1 and 4 weeks after surgery. APA enzyme and protein expression was evaluated in kidney sections. Total APA enzyme activity and mRNA expression was assessed in isolated glomeruli. Degradation of exogenous ANG II by isolated glomeruli was measured with reverse-phase high-performance liquid chromatography.

Results. APA enzyme activity, protein, and mRNA expression were stimulated in the clipped kidney 1 week after surgery compared with the contralateral kidney or normal controls. In contrast, 4 weeks after clipping APA activity and expression was higher in the contralateral kidney. In parallel to these findings, degradation of ANG II was greatest in isolated glomeruli obtained from the clipped kidney after 1 week. However, preparations from the contralateral kidney 4 weeks after surgery were more active in the metabolism of exogenous ANG II.

Conclusion. The present study provides evidence that APA is complexly regulated in in vivo situations with an activated local renin–ANG II system. ANG II appears to play a direct role in this regulation. However, since conversion of ANG II to ANG III by APA is the initial step leading to the formation of ANG IV which may exert detrimental effects not mediated through classical ANG II receptors, a local increase in APA activity may contribute to the progression of chronic renal disease even during complete AT1-receptor blockade.

Keywords: aminopeptidase A; goldblatt hypertension; progression of renal disease; renin–angiotensin system



   Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Although multiple factors may influence the progression of chronic renal diseases to end-stage renal failure, overwhelming evidence surfaced in recent years indicating that angiotensin II (ANG II) plays a pivotal role in this process [1]. ANG II could contribute to the progression of chronic renal disease by a wide variety of different mechanisms including regulation of glomerular haemodynamics, stimulation of tubular sodium reabsorption, growth induction, and profibrogenic actions [1]. Moreover, recent evidence suggest that ANG II may also exert immunological function in the kidney by induction of chemokines and proinflammatory cytokines [1].

Traditionally, almost all studies have focused on the generation of ANG II and all components of the renin–angiotensin system (RAS) have been characterized on a molecular level. The discovery of organ specific, local RAS that function independent from their systemic counterparts had added to the complex understanding of ANG II formation. However, local concentration of the small peptide ANG II may not only be determined by the generation, but also by its metabolism [2,3]. In addition, recent data have found that further degradation of ANG II leads to other peptide fragments such as angiotensin IV (ANG IV) that may bind to their own receptors exerting specific physiological actions different from ANG II [3]. Therefore, a better insight as to how the metabolism of ANG II is regulated in vivo is necessary to understand the complexity of the RAS. Aminopeptidase A (APA) (E.C. 3.4.11.7) is the major enzyme metabolizing ANG II to angiotensin III (ANG III) [2,3]. Furthermore, APA may be also involved in the degradation of angiotensin I (ANG I) and angiotensin [17]. In the kidney, APA is localized in the glomeruli (podocytes and, depending on the species, endothelial and perhaps mesangial cells as well as tubular cells, [3]. The present study was undertaken to investigate the enzyme, protein, and mRNA expression of APA in glomeruli from rats with two-kidney, one-clip (2-K 1-C) rats [4], a model which is, at least in its early phase, characterized by high ANG II levels.



   Materials and methods
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Animal Protocol
A 0.2-mm (internal diameter) silver clip was placed on right arteries of male Wistar rats weighting 150–200 g (Charles River, Sulzfeld, Germany) exactly as previously described [4]. For control animals, the right renal artery was manipulated with forceps, but no clip was placed. Two different time points were investigated: 1 and 3 weeks after clipping. At the end of the experimental period, systolic blood pressure was measured by tail plethysmography of slightly restrained unanaesthetized rats. Blood was directly collected by aortal puncture in pre-chilled EDTA tubes on ice. Plasma renin activity (PRA) was measured as the generation of ANG I per millilitre per hour with a commercial RIA (Sorin Biomedica, Saluggia, Italy). Clipped and contralateral kidneys were harvested separately, weighted, and small pieces were immediately frozen in isopentane cooled by liquid nitrogen. The remaining kidneys were subjected to differential sieving for the isolation of glomeruli using methods established for this laboratory [5].

APA enzyme activity
APA enzyme activities were measured as previously described in detail [5]. A glomerular suspension of 200 µl was incubated with 800 µl of a substrate solution containing 17.5 mM alpha-glutamyl-nitranilide (Bachem, Bubendorf, Switzerland) in 0.5 M Tris–HCl (pH 7.2) supplemented with 10 mM CaCl2. Suspensions were rotated at 37°C for 30 min. At the end of the incubation, tubes were centrifuged and the supernatants were measured at 405 nm against the substrate solution as blank [5]. Glomerular pellets were lysed and the protein content was measured by a modification of the Lowry method. APA activity was calculated as described and is expressed in µU/mg glomerular protein [5].

Degradation of ANG II by isolated glomeruli
To measure functional APA activity in glomerular suspensions, ANG II degradation was evaluated. To this end, 200 µl of isolated glomeruli suspension were incubated with 80 µg ANG II (Sigma, Deisenhofen, Germany) in PBS with 10 mM CaCl2 for 60 min at room temperature on a shaker. For selected experiments, glomeruli were preincubated for 20 min with 0.5 mM amastatin (Sigma), an inhibitor of APA and other aminopeptidases. After centrifugation, the supernatants were dried in a speed-vac whereas glomerular pellets were lysed for determination of protein content by the Lowry methods. Supernatants were redissolved in 50 µl of a 1 : 3 mixture of acetonitrile and 34.5 mM NaH2PO4 buffer (pH 6.0). Peptides were analysed by reverse-phase high-performance liquid chromatography (HPLC; M-45 pumps, 2487 Dual {lambda} Absorbance Detector, Waters, Milford, USA) using a C18 reverse-phase HPLC column (Nova-Pak, 4 µM, 3.9x150 mm, Waters) with the mobile phase consisting of a 1 : 3 mixture of acetonitrile and 34.5 mM NaH2PO4 buffer (pH 6.0) at a flow rate of 1 ml/min [6]. Retention times of synthetic peptides were 75 s for ANG II and 105 s for ANG III. Quantification of peptide concentrations was performed by Gaussian integration of peaks, compared with standards of known concentration, using the computer program GS365W (Hoefer Scientific Instruments, San Francisco, CA, USA). Pilot experiments revealed that formed ANG III was rapidly further degraded by glomeruli into smaller peptides indicating a very short half-life of ANG III, and the presence of other glomerular proteases. Therefore, data are expressed as remaining µg ANG II per mg glomerular protein rather than as de novo formed ANG III.

APA mRNA expression
Total RNA was isolated from pooled glomeruli obtained from 6–8 kidneys exactly as previously described [7]. Total RNA (20 µg) was electrophoresed through a 1.2% agarose gel with 2.2 M formaldehyde. The RNA was vacuum blotted onto a nylon membrane (Zetabind; Cuno, Meriden, USA) and UV cross-linked. For the detection of rat APA transcripts, a 3.5 kb fragment of the cDNA BP-1 (generous gift of Dr Max Cooper, Birmingham, USA) was labelled using random primers [7]. For control hybridization after stripping, a 2.0 kb insert of the plasmid pMC1 encoding the murine 18S RNA band was used. Hybridization, washing, and stripping procedures were performed exactly as previously described [7]. Exposed films were scanned with Fluor-STM multi-imager (Bio-Rad laboratories, Hercules, USA), and data were analysed with the computer program Multi-Analyst from Bio-Rad. A ratio of the intensities of the bands for APA and 18S was calculated. The intensity of the bands from control animals (sham-operation) of each independent group was assigned an arbitrary value of 1.00. Northern blots were independently repeated three times with qualitatively similar results.

Enzyme and immunohistochemistry for APA
Cryosections (5 µM-thick) were prepared. Enzyme histochemical demonstration of APA was performed as previously described with simultaneous azo-coupling using alpha-4-glutamly-methoxy-2-napthylamide (Bachem) as substrate [5].

The mouse monoclonal antibody ASD-51 generated against rat APA was used for immunohistochemistry [8]. This antibody has been previously characterized in detail [8]. Cryosections (7 µM-thick) were fixed for 10 min in acetone at -20°C. Endogenous peroxidase was blocked with 0.3% H2O2 in PBS for 30 min. The hybridoma culture supernatant containing the mouse monoclonal anti-rat APA antibody was used undiluted. Detection of antibody binding was performed using the avidin–biotin complex method (Vectastain EliteTM, Vector Laboratories, Burlingame, USA) according to the manufacturer's recommendations. Sections were counterstained with haematoxylin. As a negative control, sections were incubated with normal mouse serum. The intensity of the glomerular enzyme- and immunohistochemistry was semi-quantitatively evaluated by an investigator blinded to the origin of the various section. The following score was used: no staining or very weak staining, 1; medium staining, 2; strong staining, 3, very strong staining, 4.

Statistical analysis
All data are presented as the means±SEM. Statistical significance between different groups was first tested with Kruskal–Wallis test. Individual groups were then tested using the Wilcoxon–Mann–Whitney test. A P value of <0.05 was considered significant.



   Results
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Body weights, kidney weights, systolic blood pressure, and plasma renin activities
Table 1Go reveals basic parameters 1 and 4 weeks after clipping. There was no significant difference in systolic blood pressure between controls and clipped rats after 1 week. However, a significant increase was observed in clipped rats after 4 weeks of surgery (Table 1Go). As predicted, the weight of the contralateral kidneys increased compared with the clipped kidney (Table 1Go). Systemic PRA were stimulated 1 and 4 weeks after clipping (Table 1Go).


View this table:
[in this window]
[in a new window]
 
Table 1. Body weights, kidney weights, systolic blood pressure, plasma renin activities

 

APA enzyme activity in isolated glomeruli and enzyme histochemistry
Table 2Go shows APA enzyme activities in isolated glomeruli of the diverse groups. One week after clipping, APA activity was significantly higher in glomeruli isolated from the clipped kidney compared with the contralateral kidney or sham-operated controls. In contrast, 4 weeks after surgery, APA activity was highest in glomeruli from contralateral kidneys whereas enzyme activities from isolated glomeruli harvested from clipped kidneys returned to base-line levels.


View this table:
[in this window]
[in a new window]
 
Table 2. APA enzyme activity in isolated glomeruli

 
To further gain insight into the capacity of isolated glomeruli to directly degrade ANG II, suspensions of isolated glomeruli from various animals were incubated with exogenous ANG II under standard conditions. As newly formed ANG II was rapidly degraded by isolated glomeruli to peptide fragments, we measured the amounts of ANG II remaining in the supernatants, normalized per mg glomerular proteins, by HPLC. As shown in Table 3Go, the concentration ANG II was principally inverse correlated with APA enzyme activities. Thus, glomeruli isolated from the clipped kidney 1 week after surgery split more ANG II than preparations from the contralateral kidney or normal controls. Along this line, more ANG II was degraded by glomeruli obtained from contralateral kidneys 4 weeks after clipping (Table 3Go). Preincubation with amastatin, an APA inhibitor, though not specific for this enzyme, abolished the decrease in ANG II indicating that mainly APA is responsible for the degradation of ANG II (Table 3Go).


View this table:
[in this window]
[in a new window]
 
Table 3. Amount of exogenous ANG II remaining in the supernatant after 1 h of incubation at room temperature

 
Figure 1AGo–FGo displays enzyme histochemical staining for APA on cryosections under defined conditions. Under the chosen incubation conditions, there was only very little glomerular APA staining in controls at 1 and 4 weeks whereas the brush border of proximal tubules showed a stronger staining (Fig. 1AGo and DGo). However, 1 weeks after clipping, the staining intensity for glomerular APA increased in clipped kidneys (Fig. 1BGo) compared with contralateral kidneys (Fig. 1CGo) or controls (Fig. 1AGo). In contrast, after 4 weeks APA staining was strongest in glomeruli from the contralateral kidneys (Fig. 1FGo). A semiquantitative evaluation of glomerular staining intensities is shown in Table 4Go.



View larger version (61K):
[in this window]
[in a new window]
 
Fig. 1. Enzymehistochemical staining for APA on cryosections. There was only little staining localized in glomeruli and the brush border of proximal tubules in control rats at 1 (A) and 4 (D) weeks. At 1 week after surgery, APA staining was stronger in the clipped (B) compared with the contralateral kidney (C). However, 4 weeks after clipping this pattern was reversed and APA staining was strongest in glomeruli from the contralateral kidneys (F) compared with the clipped organ (E). Magnification x400.

 

View this table:
[in this window]
[in a new window]
 
Table 4. Semiquantitative scoring of enzyme and immunohistochemistry

 

APA mRNA expression
Figure 2Go shows an exemplary Northern blot of total RNA prepared from isolated glomeruli. APA mRNA expression increased in clipped kidneys after 1 week compared with controls or the contralateral kidneys (controls after 1 weeks: 1.00±0.0, clipped kidneys after 1 week: 1.44±0.3*, contralateral kidneys after 1 week: 0.78±0.2#; relative changes in RNA expression normalized to 18S, *P<0.05 versus controls, #P<0.05 versus clip, n=3). In contrast, APA transcripts were highest in the contralateral kidneys 4 weeks after clipping (controls after 4 weeks: 1.00±0.0, clipped kidneys after 4 week: 1.23±0.3, contralateral kidneys after 4 week: 3.00±0.72*#; relative changes in RNA expression normalized to 18S, *P<0.05 versus controls, #P<0.05 versus clip n=3).



View larger version (41K):
[in this window]
[in a new window]
 
Fig. 2. Northern blot for APA. Isolated glomeruli were obtained at 1 and 4 weeks after surgery. At 1 week, glomeruli isolated from clipped kidneys exhibited more APA transcripts than preparations from the contralateral kidneys or controls. In contrast, APA mRNA expression was higher in glomeruli isolated from contralateral kidneys 4 weeks after surgery. This blot is representative of three independent experiments with qualitatively similar results.

 

APA protein expression
Normal kidneys from sham-operated control rats at 1 and 4 weeks revealed a moderate intensity of staining for APA protein using the monoclonal antibody ASD-51 (Fig. 3AGo and DGo). There was a stronger staining in the clipped kidney at 1 week after surgery (Fig. 3BGo) compared with time-matched contralateral kidneys (Fig. 3CGo). However, a stronger staining was present in hypertrophic contralateral kidneys 4 weeks after clipping (Fig. 3FGo) compared with clipped kidneys (Fig. 3EGo). A semiquantitative evaluation of glomerular immunohistochemistry is shown in Table 4Go.



View larger version (85K):
[in this window]
[in a new window]
 
Fig. 3. Immunohistochemical staining for APA protein using a specific monoclonal antibody generated against rat APA. There was a moderate glomerular staining for APA protein in normal controls at 1 (A) and 4 (D) weeks. There was a stronger staining in the clipped kidney at 1 week after surgery (B) compared with contralateral kidneys (C). A stronger staining was present in hypertrophic contralateral kidneys 4 weeks after clipping (F) compared with clipped kidneys (E). Magnification x800.

 



   Discussion
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
APA is a homodimeric type II membrane-bound peptidase that specifically cleaves the N-terminal aspartyl residues from ANG II leading to the generation of ANG III [2,9]. Furthermore, APA also cleaves ANG I to form (des-Asp)ANG I which can be further metabolized by ACE to ANG III [2]. Finally, APA may be involved in the inactivation of the heptapeptide ANG(1–7). APA activity is enhanced by various divalent cations, particularly calcium [2].

After binding of ANG II to its putative receptors, receptor-mediated endocytosis and recycling of receptors have been described [10]. It is imaginable that local ANG II which is present in the microenvironment is degraded by APA localized on the same or adjacent cells than ANG II receptors during diffusion to the receptors. In addition, the effect of surging ANG II concentrations may be limited by APA-mediated degradation before remaining ANG II could bind to recycled empty receptors potentially inducing a second wave of signal transduction.

Indeed, several in vivo observations indicate that APA is closely involved in ANG II metabolism. For example, inhibition of APA activity in vivo using specific inhibitors induces a modest increase in systemic blood pressure [11]. On the other hand, in mice the injection of an antibody directed against the enzymatic centre of APA stimulates acute albuminuria associated with inhibition of APA activity [12]. Administration of an ACE-inhibitor or an AT1-receptor antagonists abolished this proteinuria strongly suggesting that an increase in ANG II concentration after antibody-mediated inhibition of APA plays an important role in this model [12]. Furthermore, central nervous actions of ANG II such as the control of vasopressin release are actually caused by ANG III indicating that local conversion by APA is important in mediating effects of ANG II in the brain [2]. On B-lymphocytes, APA serves as an differentiation marker of unknown function [2].

We and others have previously investigated APA enzyme activity in the kidney in situations with a stimulated RAS [5,7,1216]. Treatment of normal rats with furosemide to induce volume depletion leads to a significant increase in glomerular APA activity [5]. Direct infusion of exogenous ANG II in concentrations that induce hypertension leads to an increase in glomerular APA activity [15]. However, the situation with an endogenous activated RAS may be more complex. We have previously investigated APA enzyme activity and mRNA expression in glomeruli of rats subjected to renal ablation, a model with a known activation of the intrarenal RAS [7]. APA enzyme activity significantly increased 5 weeks after ablation [7]. However, this strong increase in enzyme activity was only accompanied by a rather modest stimulation of transcripts indicating that APA activity is mainly regulated by posttranscriptional mechanisms in this model of chronic renal injury [7]. Although glomerular APA activity as well as mRNA expression significantly increased in parallel in rats with insulin-dependent diabetes mellitus compared with normoglycaemic controls, application of insulin suppressed only APA mRNA expression but failed to have any effect on enzyme activity [14]. These findings suggest that APA mRNA and enzyme activity may be differentially regulated under certain pathophysiological conditions.

To obtain more insight into the interaction between ANG II and APA, we studied a classical in vivo model of an activated RAS, namely rats with 2-K 1-C Goldblatt hypertension. In contrast to our previous observations in the remnant kidney model and in diabetic rats [7,14], APA enzyme activity, conversion of ANG II to ANG III, as well as APA protein and mRNA expression were concomitantly regulated. We observed a biphasic pattern of glomerular APA expression. One week after clipping, APA enzyme activity and mRNA expression was higher in the clipped kidney compared with the contralateral organ or sham-operated controls, In contrast, 4 weeks after clipping, APA was upregulated in the contralateral kidney, whereas expression in the clipped kidney decreased to base-line levels. We observed this biphasic response not only by measuring APA enzyme activity, mRNA and protein expression, but provide also some functional data that isolated glomeruli from the groups with increased APA expression metabolized ANG II to a greater extent. This increased degradation of ANG II was inhibited by amastatin suggesting that the disappearance of ANG II from the supernatant is not simply caused by increased binding to receptors. However, although amastatin is widely used as an inhibitor of APA, this substance may also inhibit other aminopeptidases. Thus, it is possible that other ANG II metabolizing glomerular enzymes may be activated in addition to APA.

Although the mechanism of this biphasic induction of APA is currently unknown and requires further studies, it shows similarity with the regulation of AT1-receptors which are down-regulated already after a few days in the clipped kidney, probably due to high intra-renal ANG II concentrations. If APA expression is directly induced by ANG II as suggested by several studies [15,16], target cells that could upregulate APA must sense the increased ANG II concentration in the local micro-environment. This sensing mechanism most likely involves AT1-receptors because treatment with ANG II-receptor antagonists abolishes APA expression in situations with a stimulated RAS [12]. Thus, down-regulation of AT1-receptors in the clipped kidney at latter time points (>1 week) may very well explain why APA is only initially upregulated in the stenotic kidney [17,18]. A less likely explanation for the increased APA expression in the contralateral kidney at 4 weeks may be a persisting increase in intrarenal ANG II concentrations in the contralateral kidney accompanied by a normalization of the systemic RAS [18]. However, a fall in the systemic PRA has been only described at much latter time-points (>12 weeks) in dogs with 2-K 1-C and not necessarily in the rat model [18].

During the preparation of our manuscript, we learned of a similar study by Song and Healy [16]. In accordance with our results, these investigators found a significant increase of APA enzyme activity and transcript expression in the contralateral kidney 4 weeks after clipping [16]. In contrast to our study, Song and Healy also found an increase in enzyme histochemical staining for APA in the clipped kidney after 4 weeks [16]. However, transcript expression at earlier time-points was not evaluated in this study. Although the reason for this somewhat discrepancy to our study is currently unclear, APA enzymehistochemistry as used in the study of Song and Healy is certainly not totally specific for this protease and may be also difficult to quantify.

We have recently overexpressed APA in cultured mouse mesangial cells which do normally not possess this peptidase [13]. In contrast to wild type cells or cells being transfected with a control construct, ANG II failed to stimulate proliferation and intracellular inositol 1,4,5-triphosphate accumulation in APA overexpression cells indicating that major functions of the vasopeptide were abolished [13]. Furthermore, inhibition of APA activity in overexpressing mesangial cells with amastatin or an specific APA-inhibiting monoclonal antibody restored the function of exogenous ANG II on these cells [13]. Although we have not directly measured the degradation of ANG II in these in vitro experiments, the study suggest that expression of APA may very well regulate the function of ANG II in the local microenvironment [13].

On the other hand, an increase in ANG II degradation may not necessarily imply a protective mechanism for renal function because APA metabolizes ANG II into ANG III [2,3]. Although ANG III exerts less affinity for the AT1-receptor than ANG II, ANG III stimulates profibrogenic cytokines such as TGF-ß and increases the synthesis of extracellular matrix in cultured mesangial cells and renal fibroblasts [19,20]. A recent study showed that ANG III formed by APA could effectively induce calcium influx in several nephron segments of the rat [20]. Moreover, ANG III itself is cleaved by non-specific proteases such as aminopeptidase M to ANG IV [3]. These aminopeptidases are almost ubiquitously distributed in the kidney including in mesangial and tubular cells [3]. ANG IV exhibits distinct effects that are different from those of ANG II and ANG III and binds to its own receptor, named AT4. Such specific receptors for ANG IV have been characterized on endothelial, mesangial, proximal tubular as well as collecting duct cells [2123]. This AT4-receptors are not blocked by conventional AT1-receptor antagonists. ANG IV may have potential profibrogenic effects and it has been described in endothelial and tubular cells that this ANG II-fragment stimulates the expression of plasminogen activator inhibitor leading to a decrease in extracellular matrix turnover [2123]. Therefore, an up-regulation in APA expression could induce detrimental effects on the kidney by enhancing the formation of active ANG II-fragments that bind to other receptors than the parental peptide.



   Acknowledgments
 
We thank R. Schroeder and I. Jacob for excellent technical help. This work was supported by the Deutsche Forschungsgemeinschaft (Wo 460/2–3, 2–4; and a Heisenberg fellowship to G.W.).



   Notes
 
Correspondence and offprint requests to: Gunter Wolf, MD, University of Hamburg, University Hospital Eppendorf, Department of Medicine, Division of Nephrology and Osteology, Pavilion 61, Martinstraße 52, D-20246 Hamburg, Germany. Back



   References
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 

  1. Wolf G. Angiotensin II is involved in the progression of renal disease: importance of non-hemodynamic mechanisms. Néphrologie1998; 19: 451–456
  2. Wolf G, Mentzel S, Assmann KJM. Aminopeptidase A. a key enzyme in the intrarenal degradation of angiotensin II. Exp Nephrol1997; 5: 364–369[ISI][Medline]
  3. Ardaillou R, Chansel D. Synthesis and effects of active fragments of angiotensin II. Kidney Int1998; 52: 1458–1468[ISI]
  4. Wolf G, Schneider A, Wenzel U, Helmchen U, Stahl RAK. Regulation of glomerular TGF-ß expression in the contralateral kidney of two-kidney, one-clip hypertensive rats. J Am Soc Nephrol1998; 9: 763–772[Abstract]
  5. Wolf G, Thaiss F, Scherberich JE, Schoeppe W, Stahl RAK. Glomerular angiotensinase A in the rat: increase of enzyme activity following renal ablation. Kidney Int1990; 38: 862–868[ISI][Medline]
  6. Seikaly MG, Arant BS, Sebey FD. Endogenous angiotensin concentrations in specific intrarenal fluid compartments of the rat. J Clin Invest1990; 86: 1352–1357[ISI][Medline]
  7. Wolf G, Thaiss F, Mueller E et al. Glomerular mRNA expression of angiotensinase A after renal ablation. Exp Nephrol1995; 3: 240–248[ISI][Medline]
  8. Mentzel S, Van Son JPHF, Dijman HPM, Wetzels JFM, Assmann KJM. Induction of albuminuria in mice: synegistic effect of two monoclonal antibodies directed to different domains of aminopeptidase A. Kidney Int1999; 55: 1335–1347[ISI][Medline]
  9. Zini S, Fournie-Zaluski MC, Chauvel E, Roques BP, Corvol P, Elorens-Cortes C. Identification of metabolic pathways of brain angiotensin II and III using specific aminopeptidase inhibitors: predominant role of angiotensin III in the control of vasopressin release. Proc Natl Acd Sci USA1996; 93: 11968–11973[Abstract/Free Full Text]
  10. Ullian ME, Linas SL. Role of receptor cycling in the regulation of angiotensin II surface receptor number and angiotensin II uptake in rat vascular smooth muscle cells. J Clin Invest1989; 84: 840–846[ISI][Medline]
  11. Ahmad S, Ward PE. Role of aminopeptidase activity in the regulation of the pressor activity of circulating angiotensins. J Pharmacol Exper Therap1990; 252: 643–650[Abstract]
  12. Mentzel S, Assmann KJM, Dijkman HBPM et al. Inhibition of aminopeptidase A activity causes an acute albuminuria in mice: an angiotensin II-mediated effect? Nephrol Dial Transplant1996; 11: 2163–2169[Abstract]
  13. Wolf G, Assmann KJM, Stahl RAK. Overexpression of aminopeptidase A abolishes the growth promoting effects of angiotensin II in cultured mouse mesangial cells. Kidney Int1997; 52: 1250–1260[ISI][Medline]
  14. Thaiss F, Wolf G, Assad N, Zahner G, Stahl RAK. Angiotensinase A gene expression and enzyme activity in isolated glomeruli of diabetic rats. Diabetologia1996; 39: 275–280[Medline]
  15. Johnson RJ, Alpers CE, Yoshimura A et al. Renal injury form angiotensin II-mediated hypertension. Hypertension1992; 19: 464–474[Abstract]
  16. Song L, Healy DP. Kidney aminopeptidase A and hypertension, part II. Effects of angiotensin II. Hypertension1999; 37: 746–752
  17. Della Bruno R, Bernhard I, Gess B, Schricker K, Kurtz A. Renin gene and angiotensin II AT1 receptor gene expression in the kidneys of normal and of two-kidney/one-clip rats. Eur J Physiol1995; 430: 265–272[ISI][Medline]
  18. Martinez-Maldonado M. Pathophysiology of renovascular hypertension. Hypertension1991; 17: 707–719[Abstract]
  19. Ruiz-Ortega M, Lorenzo O, Egido J. Angiotensin III up-regulates genes involved in kidney damage in mesangial cells and renal interstitial fibroblasts. Kidney Int1998; 54 [Suppl. 68]: S41–S45[ISI]
  20. Hus-Citharel A, Gasc JM, Marchetti J, Roques B, Corvol P, Llorens-Cortes C. Aminopeptidase A activity and angiotensin III effects on [Ca2+]i along the rat nephron. Kidney Int1999; 56: 850–859[ISI][Medline]
  21. Kerins DM, Hao Q, Vaughan DE. Angiotensin induction of PAI-1 expression in endothelial cells is mediated by the hexapeptide angiotensin IV. J Clin Invest1995; 96: 2515–2520[ISI][Medline]
  22. Chansel D, Czekalski S, Vandermeersch S, Ruffet E, Fournié-Zaluski MC, Ardaillou R. Characterization of angiotensin IV-degrading enzymes and receptors on rat mesangial cells. Am J Physiol1998; 275: F535–F542[Abstract/Free Full Text]
  23. Gesualdo L, Ranieri E, Monno R et al. Angiotensin IV stimulates plasminogen activator inhibitor-1 expression in proximal tubular epithelial cells. Kidney Int1999; 56: 461–470[ISI][Medline]
Received for publication: 6. 1.00
Revision received 13. 7.00.



This Article
Abstract
FREE Full Text (PDF)
Alert me when this article is cited
Alert me if a correction is posted
Services
Email this article to a friend
Similar articles in this journal
Similar articles in ISI Web of Science
Similar articles in PubMed
Alert me to new issues of the journal
Add to My Personal Archive
Download to citation manager
Search for citing articles in:
ISI Web of Science (3)
Disclaimer
Request Permissions
Google Scholar
Articles by Wolf, G.
Articles by Stahl, R. A. K.
PubMed
PubMed Citation
Articles by Wolf, G.
Articles by Stahl, R. A. K.