Ureteric bud derivatives express angiotensinogen and AT1 receptors

MINOLFA PRIETO1,2, SUSANA DIPP1, SUZANNE MELEG-SMITH3 and SAMIR S. EL-DAHR1,2

1 Departments of Pediatrics
2 Physiology
3 Pathology, Tulane University School of Medicine, New Orleans, Louisiana 70112


    ABSTRACT
 TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Inactivation of the renin-angiotensin system interferes with the morphogenesis of the renal medulla. Thus ureteric bud (UB) derivatives may be a target for angiotensin production and action. To begin to test this hypothesis, we examined the cellular expression of angiotensinogen (Ao) and AT1 receptor proteins during rat metanephrogenesis by immunohistochemistry. In addition, we tested whether UB-derived cells in culture express the Ao and AT1 proteins. On embryonic day E15, Ao and AT1 are expressed in the UB branches and stromal mesenchyme. S-shaped bodies, including the vascular cleft, express AT1 but not Ao. The metanephric mesenchyme and pretubular aggregates are Ao negative and AT1 negative. Expression of Ao and AT1 in UB branches and ampullae is also observed on E16. However, UB expression of Ao is transient and is no longer detectable in the developing distal nephron beyond E17. On E17, both Ao and AT1 are expressed in capillary loop glomeruli and proximal tubules, whereas UB branches express AT1 only. By E18, the majority of Ao immunoreactivity is clustered in terminally differentiated proximal tubules, whereas AT1 receptors are expressed in both proximal and distal nephron segments. The specificity of Ao and AT1 staining was documented by the elimination/attenuation of immunoreactivity after preadsorption of the primary antibodies with their respective antigens. Consistent with the in vivo findings, the AT1 protein is abundantly expressed in cellular lysates of mouse UB (E11.5) and IMCD3 (adult) cells. Moreover, AT1 receptors in UB and IMCD3 cells are functional, since angiotensin II treatment elicits the tyrosine phosphorylation of the mitogen-activated protein kinases, ERK1/2. To our knowledge, this is the first demonstration of Ao and AT1 protein expression in the developing distal nephron. Angiotensin II may have a paracrine role in the ontogeny of the collecting system.

nephrogenesis; renal medulla; collecting duct; proximal tubule; immunohistochemistry


    INTRODUCTION
 TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
THE RENIN-ANGIOTENSIN SYSTEM is essential for the structural and functional maturation of the metanephric kidney (reviewed in Refs. 2, 5, and 8). For example, treatment of newborn rats with an antagonist of the AT1 receptor (6, 30), or elimination of both subtypes of the AT1 receptor (22, 28), angiotensinogen (Ao) (14, 18, 19), or angiotensin-converting enzyme (4, 15), by gene targeting in mice produce specific defects in the development of the renal microvasculature and the renal papilla. Moreover, biochemical studies have demonstrated that the synthesis of renal renin and angiotensin peptides peaks perinatally and declines dramatically during postnatal maturation (9, 32).

Although angiotensin II is clearly required for normal renal development and function, little is known regarding the specific developmental steps that are dependent on angiotensin actions. Previous studies have reported that AT1 receptor transcripts and binding sites are diffusely expressed in the nephrogenic zone (7, 13, 20, 25, 26, 29), implicating angiotensin II in various stages of nephron maturation ranging from early epithelialization to tubular and glomerular differentiation. Moreover, the papillary hypoplasia in AT1/Ao/angiotensin converting enzyme (ACE)-deficient mice suggested for the first time that angiotensin II may also be required for ureteric bud (UB) growth and differentiation. However, such a hypothesis requires the demonstration of a potential angiotensin-producing/responsive system in the differentiating distal nephron. In this study, we examined the cellular localization of Ao and AT1 receptor proteins during renal morphogenesis. Our specific objectives were: 1) to determine whether Ao and AT1 are expressed in UB-derived tubules and cells, and 2) to correlate the spatiotemporal expression of Ao and AT1 with cellular growth and differentiation in vivo.


    METHODS
 TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Immunohistochemistry
Immunolocalization of Ao and AT1 was carried out in Sprague-Dawley rat embryos (E) ranging in age from days E15 to E19 (n = 4 per age group; Hybrid-Ready Tissue, Novagen). Embryos were fixed in 10% buffered formalin, dehydrated in graded solutions of alcohol, embedded in paraffin blocks, and 7-µm sections were made and mounted onto slides with Vectabond (Vector Laboratories). Immunostaining was performed by the immunoperoxidase technique using the Vectastain Elite kit (Vector Laboratories, Burlingame, CA) as previously described (11). Briefly, after deparaffinization in xylene and hydration in 95 to 70% alcohol, the sections were washed in PBS (pH 7.2) for 5 min. Quenching of endogenous peroxidase activity was performed by treating the sections with 0.3% H2O2 in methanol for 30 min. After washing in PBS for 20 min, the sections were incubated with the blocking antibody (normal horse or rabbit serum) for 20 min. Thereafter, the sections were incubated for 90 min with the primary antibody diluted in PBS containing 1% BSA. Sections were rinsed in PBS for 10 min and subsequently incubated with IgG-biotinylated antibody (anti-rabbit or anti-sheep) for 30 min. Subsequently, the sections were washed in biotinylated horseradish peroxidase complex and exposed for 5–7 min to 0.1% diaminobenzidine tetrahydrochloride and 0.2% H2O2. The slides were then washed in tap water and counterstained with hematoxylin.

The primary antibodies utilized in this study were used as follows: 1) a polyclonal anti-rat Ao antibody raised in the sheep was used at concentrations of 1/2,000 to 1/8,000 (generously provided by Dr. Conrad Sernia) (3); 2) a polyclonal rabbit AT1 receptor antibody directed against the NH2-terminal domain of the human receptor (identical sequence in rat) (Santa Cruz, N-10, sc-1173) was used at concentrations of 1/200 to 1/800 (1); and 3) a monoclonal antibody against proliferating cell nuclear antigen (PCNA) (clone PC10; DAKO, Carpenteria, CA) was used at a concentration of 1/200. Controls consisted of tissue sections in which the Ao and AT1 antibodies were preadsorbed with either Ao-rich plasma or the AT1 peptide sequence, respectively (11). Additional controls included sections where the primary antibodies were substituted with buffer or nonimmune serum.

Western Blot Analysis
Kidneys, mouse embryonic UB cells originally isolated from day E11.5 mouse generously provided by Jonathan Barasch, Columbia University, and inner medullary collecting duct cells (IMCD3, American Type Culture Collection) were homogenized in cold lysis buffer (50 mM Tris·HCl, pH 8.0, 150 mM NaCl, 0.02% sodium azide, 0.1% SDS, 1% Nonidet P-40, and 0.5% deoxycholate) containing a cocktail of enzyme inhibitors added fresh to the lysis buffer (100 µg/ml phenylmethylsulfonyl fluoride, 1 µg/ml aprotinin, 1 µg/ml leupeptin, and 10 µg/ml Na3VO4). Insoluble material was removed by centrifugation for 10 min at 14,000 g at 4°C. Proteins (20 µg) were resolved on 10% SDS-polyacrylamide gels and transferred to nitrocellulose membranes. The adequacy of transfer was assessed by Ponceau-S staining of the membranes. Nonspecific binding sites were blocked with a blocking solution (PBS containing 0.1% Tween and 3% BSA) overnight at 4°C. Membranes were then incubated with the Ao (1/1,000), AT1 receptor (1/400), ERK (New England Biolabs, 1/200), or ß-actin (from Sigma, diluted 1/4,000) antibodies at room temperature for 1 h. After three washes in PBS/Tween, the nitrocellulose membrane was exposed for 1 h at room temperature to the secondary antibody. Immunoreactive bands were visualized using the enhanced chemiluminescence detection system (ECL, Amersham), per manufacturer’s recommendations. The immunoblots were then exposed to Hyperfilm-ECL films.

Cell Culture
UB and IMCD3 cells were maintained in minimum essential medium supplemented with 10% fetal bovine serum, penicillin (100 U/ml), and streptomycin (100 µg/ml) (Life Technologies) at 37°C in a humidified incubator with 5% CO2. The cells were treated with angiotensin II (10-7 M), and whole cell lysates were collected at 0–15 min after treatment. Proteins were separated by SDS-PAGE and blotted on nitrocellulose followed by immunoblotting with anti-phospho-ERK antibodies. Signal detection was performed using ECL (Amersham).


    RESULTS
 TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Immunohistochemical Localization of Ao and AT1
Kidney tissue sections from each age group were immunostained in the same run for Ao and AT1 utilizing several dilutions of the respective antibodies. The intensity of Ao and AT1 immunoreactivity was relatively low during early embryonic kidney development and increased substantially toward the end of gestation. For example, on day E15, detection of Ao staining was not possible at antibody dilution higher than 1/2,000. In comparison, Ao immunoreactivity was easily visualized at dilutions of 1/6,000 on day E17 and 1/8,000 on day E19. For AT1, antibody concentrations ranged from 1/200 on day E15 to 1/800 on day E18.

Angiotensinogen
Day E15.
Ao immunoreactivity was observed in the loose stromal mesenchyme (Fig. 1A) and on apical membranes of UB branches (Fig. 1B). The epithelial anlagen in the nephrogenic zone (pretubular aggregates, comma-shaped bodies, and S-shaped bodies) were Ao negative. Control sections incubated with nonimmune serum in lieu of the primary antibody (Fig. 1C) or in which the primary antibody was preadsorbed with Ao-rich plasma (Fig. 1D) showed no specific staining. Compared with the kidney, the adrenal gland and liver contained greater Ao immunoreactivity in the day E15 embryo (Fig. 1A).



View larger version (158K):
[in this window]
[in a new window]
 
Fig. 1. Localization of angiotensinogen (Ao) in the metanephric rat kidney on embryonic day 15 (E15). Ao antibody concentration is 1/2,000. A: low-power view showing stronger Ao immunostaining in the liver (Liv) and adrenal gland (Ad) than the kidney (Kid). B: high-power view showing Ao immunoreactivity in ureteric bud (UB) (arrows) and surrounding stromal mesenchyme (SM). Primitive nephrons [comma-shaped (c) and S-shaped (S) bodies] are Ao negative. C: a control section incubated with nonimmune serum shows lack of staining. D: a consecutive section to B, in which the Ao antibody was preadsorbed with Ao-rich plasma, showing markedly attenuated Ao immunostaining.

 
Day E16.
Ao was detectable with antibody concentration of 1/4,000 (Fig. 2). Ao immunoreactivity was observed in the UB branches and their ampullae (Fig. 2, AC). Ao was also expressed in early proximal tubules and capillary loop stage glomeruli, whereas the glomerular epithelial cells were Ao negative (Fig. 2D).



View larger version (150K):
[in this window]
[in a new window]
 
Fig. 2. Localization of Ao in the metanephric kidney on E16. Ao antibody concentration is 1/4,000. A and B: Ao immunostaining is present in ampulla (Amp) of UB branches. The surrounding metanephric condensate (MC) does not express Ao. C: high-power view showing a bifurcating UB expressing immunoreactive Ao. The metanephrogenic mesenchyme (MM) is weakly positive. D: diffuse Ao staining is observed in a tubule associated with a cup-shaped glomerulus. Ao is expressed in the glomerular tuft (arrow).

 
Day E17.
Ao immunoreactivity was detected at antibody concentration of 1/6,000 and was prominent in the tubules associated with mature glomeruli (Fig. 3A). Closer examination of Ao-containing structures revealed the presence of staining along the luminal aspect of proximal tubules (Fig. 3, B and C). Ao immunostaining was observed for the first time in S-shaped bodies on both luminal and basolateral aspects of the epithelial cells destined to give rise to the proximal tubule as well as in glomeruli (Fig. 3D). Of interest is that UB branches and tips became Ao negative at this developmental stage. Thus Ao expression in the developing distal nephron occurs early and transiently and shifts to proximal tubules with further differentiation.



View larger version (167K):
[in this window]
[in a new window]
 
Fig. 3. Localization of Ao in the metanephric kidney on day E17. Ao antibody concentration is 1/6,000. A: low-power view showing predominant expression of Ao in deep cortical proximal tubules (PT). The epithelial anlagen are Ao negative. Note the absence of Ao from the collecting ducts at this stage. B: Ao is expressed on the apical surface of a well-differentiated PT. Other positive structures include the glomerular mesangium (G) and surrounding interstitial cells. C: Ao is expressed on the apical aspect of an early PT. D: a capillary loop stage glomerulus showing expression of Ao in a mesangial pattern; the early PT is Ao positive, whereas the distal tubule (DT) is not.

 
Day E19.
At this stage, there was an obvious surge in the intensity of Ao staining, and Ao immunoreactivity was easily detectable using antibody concentration of 1/8,000. Ao was restricted to proximal tubules (Fig. 4), reminiscent of its localization in the adult kidney (12). Unlike capillary loop stage glomeruli, fully mature glomeruli were Ao negative. Nuclear PCNA immunoreactivity was present in the nephrogenic zone (Fig. 4). The cells at these sites were Ao negative. Conversely, Ao-containing proximal tubular cells were, for the most part, PCNA negative. The medullary rays were PCNA-positive but Ao negative (Fig. 4, B and C). Thus Ao expression is clustered in more differentiated structures toward the end of nephrogenesis.



View larger version (160K):
[in this window]
[in a new window]
 
Fig. 4. Complementary spatial expression of Ao and proliferating cell nuclear antigen (PCNA) in the metanephric kidney on day E19. Ao antibody concentration is 1/8,000. A: low-power view showing distinct expression of Ao in the PT (original magnification, x10). B: at higher magnification, Ao is observed in well-differentiated PT. The tubular structures in the nephrogenic zone (NZ), glomeruli (G), and medullary rays (MR) are Ao negative (original magnification, x20). C: by comparison, PCNA (a marker of proliferating cells) is expressed in NZ, G, and MR (original magnification, x20).

 
Angiotensin II Type 1 Receptor (AT1)
The antibody utilized in this study is directed against an NH2-terminal peptide sequence that is identical in the AT1A and AT1B receptors. Accordingly, the following description, referred to as AT1, encompasses both receptor subtypes.

Day E15.
AT1 was detectable using antibody concentrations of 1/200. AT1 immunoreactivity was present in the epithelial cells of S-shaped bodies and in the vascular cleft (Fig. 5, AC). The stromal mesenchyme was also AT1 positive. UB branches were strongly positive for AT1 on both apical and basolateral membranes (Fig. 6, AC). Thus, at this early stage of nephrogenesis, AT1 receptors are preferentially expressed in epithelialized structures of the nephrogenic zone and in the UB branches.



View larger version (149K):
[in this window]
[in a new window]
 
Fig. 5. Kidney AT1 receptor localization on day E15. AC: AT1 is detectable using antibody concentrations of 1/200. AT1 immunoreactivity is present in the epithelial cells of S-shaped bodies and in the vascular cleft. The stromal mesenchyme is also AT1 positive. D: control section incubated with AT1 antibody preadsorbed with the antigenic sequence, showing lack of staining.

 


View larger version (94K):
[in this window]
[in a new window]
 
Fig. 6. Kidney AT1 localization on day E16. AC: UB branches are strongly positive for AT1 on both apical and basolateral membranes (arrows in C).

 
Day E17.
AT1 antibody concentrations of 1/400 were adequate in visualizing the receptor. AT1 immunoreactivity remained positive in S-shaped nephrons and on apical and basolateral membranes of UB branches (Fig. 7, AC). In addition, AT1 receptors were observed in new locations such as the mesangium of capillary loop stage glomeruli (Fig. 7B). The metanephrogenic mesenchyme and metanephric condensates showed extremely weak reactivity to the AT1 antibody (Fig. 7, A and C).



View larger version (103K):
[in this window]
[in a new window]
 
Fig. 7. Kidney AT1 immunolocalization on day E17. A and B: AT1 immunoreactivity is positive in a UB and its branches. C: strong AT1 expression in UB branches and tuft of capillary loop stage glomeruli (G). The stromal mesenchyme (SM) is also AT1 positive. V, vesicle.

 
Day E18.
AT1 immunoreactivity was specifically enhanced in the differentiating proximal tubules (Fig. 8A). The collecting ducts continued to express AT1 at this stage (Fig. 8B). Capillary loop and cup-shaped glomeruli exhibited AT1 staining in the tuft but not in the epithelial cells.



View larger version (103K):
[in this window]
[in a new window]
 
Fig. 8. A: kidney AT1 immunolocalization on day E18. AT1 immunoreactivity is enhanced in the differentiating PT. B: the collecting ducts (CD) express AT1 receptors predominantly on the luminal aspect with smaller amounts on the basolateral membranes. C: a cup-shaped glomerulus exhibiting AT1 staining in the tuft but not in the epithelial cells.

 
Expression of Ao and AT1 in UB-Derived Renal Epithelial Cells
To test whether renal epithelial cells of distal nephron origin express Ao and AT1, whole cell lysates from UB cells (fetal) and IMCD3 cells (adult) were probed for the Ao and AT1 proteins by Western blotting. As shown in Fig. 9A, adult mouse kidney expresses two molecular species of Ao (52 and 60 kDa). As expected from the immunohistochemical results, IMCD3 cells, which are derived from adult mouse kidney, express only trace amounts of Ao. UB cells also express very low levels of Ao. On the other hand, UB cells express abundant AT1 receptors with molecular masses varying from 41 to 75 kDa (Fig. 9B). IMCD3 cells and the adult mouse kidney homogenate contain predominantly the higher molecular weight forms of the receptor. The correlation, if any, between the molecular size of the AT1 protein and the relative expression level during differentiation is potentially very interesting but was not investigated in this study.



View larger version (49K):
[in this window]
[in a new window]
 
Fig. 9. Western blot analysis of Ao (A), AT1 (B), and ß-actin (C) in UB and IMCD3 cells (20 µg total protein/lane). Similar results were obtained in 2 independent experiments.

 
To determine whether AT1 receptors in UB and IMCD3 cells are functional and can therefore respond to ligand stimulation by activation of specific intracellular signaling pathways, the cells were treated with angiotensin II (10-7 M). Cell lysates were harvested at times of 0, 2, 5, 10, and 15 min and were subjected to Western blotting using the phospho-ERK antibody. As shown in Fig. 10, angiotensin II stimulated a time-dependent increase in ERK1/2 tyrosine phosphorylation without a change in total ERK protein levels. These findings indicate that AT receptors in collecting duct cells are functional in that they are coupled to the mitogen-activated protein kinase (MAPK) pathway.



View larger version (65K):
[in this window]
[in a new window]
 
Fig. 10. Angiotensin II (10-7 M) stimulates mitogen-activated protein kinase (MAPK) phosphorylation in IMCD3 cells. A: Western blot of IMCD3 cell lysates after treatment with angiotensin II for 0–15 min was probed with a monoclonal anti-phospho-ERK antibody that recognizes p-ERK-1 (44 kDa) and p-ERK-2 (42 kDa). B: Western blot probed with non-phospho-ERK antibody. Similar results were obtained in UB cells.

 

    DISCUSSION
 TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
The present study demonstrates the expression of Ao and AT1 proteins in UB-derived renal epithelia. In a previous study, we demonstrated AT1 protein expression in the collecting ducts of adult rat kidneys (11). Thus AT1 is expressed in the distal nephron from the early stages of branching morphogenesis until terminal differentiation. In comparison, Ao expression in the distal nephron is transient and developmentally restricted.

The ontogeny of the renin-angiotensin system components has been extensively studied in several species. It is now established that renal angiotensin II synthesis is activated during nephrogenesis (32) and that this is primarily due to enhanced renin gene expression (9). Like other components of the renin-angiotensin system, the Ao and AT1 genes are developmentally regulated in the kidney and other organs (3, 7, 10, 13, 16, 20, 23–36, 29). Functionally, blockade of ACE or AT1 receptors in newborn animals or during gestation is associated with severe abnormalities in kidney development (6, 8, 30). These abnormalities can be recapitulated by genetic disruption of the renin-angiotensin system in mice (4, 14, 15, 18, 19, 28). A major renal defect in these mutant mice is apparent hydronephrosis secondary to papillary hypoplasia, the pathogenesis of which is not well understood.

The expression of Ao and AT1 receptors in UB-derived epithelia raises the intriguing possibility for the existence of a paracrine angiotensin-generating/responsive system in the developing distal nephron. In this regard, several important questions will need to be answered. First, does the distal nephron have an intrinsic capacity to generate angiotensin II? If so, what is the nature of the angiotensin-generating enzyme? We have recently reported the presence of angiotensin II-generating kallikrein-like enzymes in the developing rat kidney (32). Since kallikreins are distal nephron enzymes, this serine protease family may be such a candidate. Second, what is the functional relevance of angiotensin II in the distal nephron? There is evidence that angiotensin II acts via basolateral AT1 to stimulate luminal alkalinization in rabbit cortical collecting duct (31) and H+-ATPase activity in rat collecting duct (27). Functional studies in AT1-deficient mice also suggest a role for angiotensin in the urinary concentrating mechanism (21). To our knowledge, direct evidence linking angiotensin II with collecting duct morphogenesis is still lacking, and the specific roles of Ao and AT1 in distal nephrogenesis remain to be explored.

An important finding of this study is the expression of Ao, along with AT1, in the developing glomerulus. A recent study found that angiotensin II displays chemotactic activity toward retinal pericytes (17), a cell type similar to glomerular mesangial cells. This raises the intriguing possibility that angiotensin II may function to recruit mesangial cell precursors into the forming glomerulus.

Comparison of Ao, AT1, and PCNA localization sites revealed that angiotensin-producing/responsive cells exhibit a differentiated phenotype. This finding suggests that, in addition to its roles in the regulation of renal growth and maturation of renal hemodynamic and excretory functions, angiotensin II may be important for the maintenance of terminal epithelial differentiation.

In summary, the present study demonstrates that Ao and AT1 receptors share common expression sites within the developing nephron. During early nephrogenesis, Ao and AT1 are expressed in UB branches and tips, the loose stromal mesenchyme, and capillary loop glomeruli. AT1 receptors (but not Ao) are expressed in S-shaped bodies and in the vascular clefts. Compared with Ao, distal nephron AT1 expression is longer lasting and persists until terminal differentiation. The presence of a paracrine angiotensin system in the developing distal nephron may explain, at least in part, why fetal interruption of renin-angiotensin function results in abnormal development of the renal medulla.


    ACKNOWLEDGMENTS
 
We are grateful to Dr. Conrad Sernia (University of Queensland, Australia) for the angiotensinogen antibody and Dr. Jonathan Barasch (Columbia University, New York) for the ureteric bud cell line.

This study was supported by a grant from the National Institutes of Health DK-56264.


    FOOTNOTES
 
Article published online before print. See web site for date of publication (http://physiolgenomics.physiology.org).

Address for reprint requests and other correspondence: S. S. El-Dahr, Tulane Univ. Health Sciences Center, Dept. of Pediatrics, SL-37, Section of Pediatric Nephrology, 1430 Tulane Ave., New Orleans, LA 70112 (E-mail: seldahr{at}tulane.edu).


    REFERENCES
 TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Ali MS, Sayeski PP, Dirksen LB, Hayzer DJ, Marrero MB, Bernstein KE. Dependence on the motif YIPP for the physical association of Jak2 kinase with the intracellular carboxyl tail of the angiotensin II AT-1 receptor. J Biol Chem 272: 23382–23388, 1997.[Abstract/Free Full Text]
  2. Coffman TM. Gene targeting in physiological investigations: studies of the renin-angiotensin system. Am J Physiol Renal Physiol 274: F999–F1005, 1998.[Abstract/Free Full Text]
  3. Darby IA and Sernia C. In situ hybridization and immunohistochemistry of renal angiotensinogen in neonatal and adult rat kidneys. Cell Tissue Res 281: 197–206, 1995.[ISI][Medline]
  4. Esther, CR Jr, Howard TE, Marino EM, Goddard JM, Capecchi MR, and Bernstein KE. Mice lacking angiotensin-converting enzyme have low blood pressure, renal pathology, and reduced male fertility. Lab Invest 74: 953–965, 1996.[ISI][Medline]
  5. Fogo A and Ichikawa I. Renin angiotensin system in development of mice and men. Am J Pathol 149: 1797–1801, 1996.[ISI][Medline]
  6. Friberg P, Sundelin B, Bohman SO, Bobik A, Nilsson H, Wickman A, Gustafsson H, Peterson J, and Adams MA. Renin-angiotensin system in neonatal rats: induction of a renal abnormality in response to ACE inhibition or angiotensin II antagonism. Kidney Int 45: 485–492, 1994.[ISI][Medline]
  7. Gimonet V, Bussieres L, Medjebeur AA, Gasser B, Lelongt B, and Laborde K. Nephrogenesis and angiotensin II receptor subtypes gene expression in the fetal lamb. Am J Physiol Renal Physiol 274: F1062–F1069, 1998.[Abstract/Free Full Text]
  8. Gomez RA and Norwood VF. Developmental consequences of the renin-angiotensin system. Am J Kidney Dis 26: 409–431, 1995.[ISI][Medline]
  9. Gomez RA, Lynch KR, Sturgill BC, Elwood JP, Chevalier RL, Carey RM, and Peach MJ. Distribution of renin mRNA and its protein in the developing kidney. Am J Physiol Renal Fluid Electrolyte Physiol 257: F850–F858, 1989.[Abstract/Free Full Text]
  10. Gomez RA, Cassis L, Lynch KR, Chevalier RL, Wilfong N, Carey RM, and Peach MJ. Fetal expression of the angiotensinogen gene. Endocrinology 123: 2298–2302, 1988.[Abstract]
  11. Harrison-Bernard LM, Navar LG, ho MM, Vinson GP, and El-Dahr SS. Immunohistochemical localization of angiotensin II AT1 receptor in the adult rat kidney using a monoclonal antibody. Am J Physiol Renal Physiol 273: F170–F177, 1997.[Abstract/Free Full Text]
  12. Ingelfinger JR, Zuo WM, Fon EA, Ellison KE, and Dzau VJ. In situ hybridization evidence for angiotensinogen messenger RNA in the rat proximal tubule. An hypothesis for the intrarenal renin-angiotensin system. J Clin Invest 85: 417–423, 1990.[ISI][Medline]
  13. Kakuchi J, Ichiki T, Kiyama S, Hogan BLM, Fogo A, Inagami T, and Ichikawa I. Developmental expression of renal angiotensin II receptor genes in the mouse. Kidney Int 47: 140–147, 1995.[ISI][Medline]
  14. Kim HS, Krege JH, Kluckman KD, Hagaman JR, Hodgin JB, Best CS, Jenette JC, Coffman TM, Maeda N, and Smithies O. Genetic control of blood pressure and the angiotensinogen locus. Proc Natl Acad Sci USA 92: 2735–2739, 1995.[Abstract]
  15. Krege JH, John SWM, Langenbach LL, Hodgin JB, Hagaman JR, Bachman ES, Jenette JC, O’Brien DA, and Smithies O. Male-female differences in fertility and blood pressure in ACE-deficient mice. Nature 375: 146–148, 1995.[ISI][Medline]
  16. Lynch KR and Peach MJ. Molecular biology of angiotensinogen. Hypertension 17: 263–269, 1991.[ISI][Medline]
  17. Nadal JA, Scicli GM, Carbini LA, Naussbaum JJ, and Scicli AG. Angiotensin II and retinal pericytes migration. Biochem Biophys Res Commun 266: 382–385, 1999.[ISI][Medline]
  18. Nagata M, Tanimoto K, Fikamizu A, Kon Y, Sugiyama F, Yagami K, Murakami K, and Watanabe T. Nephrogenesis and renovascular development in angiotensinogen-deficient mice. Lab Invest 75: 745–753, 1996.[ISI][Medline]
  19. Niimura F, Labosky PA, Kakuchi J, Okubo S, Yoshida H, Oikawa T, Ichiki T, Naftilan AJ, Fogo A, Inagami T, Hogan BLM, and Ichikawa I. Gene targeting in mice reveals a requirement for angiotensin in the development and maintenance of kidney morphology and growth factor regulation. J Clin Invest 96: 2947–2954, 1995.[ISI][Medline]
  20. Norwood VF, Craig MR, Harris JM, and Gomez RA. Differential expression of angiotensin II receptors during early renal morphogenesis. Am J Physiol Regulatory Integrative Comp Physiol 272: R662–R668, 1997.[Abstract/Free Full Text]
  21. Oliverio MI, Delnomdedieu M, Best CE, Ping L, Morris M, Callahan MF, Johnson GA, Smithies O, and Coffman TM. Abnormal water metabolism in mice lacking the type 1A receptor for ANG II. Am J Physiol Renal Physiol 278: F75–F82, 2000.[Abstract/Free Full Text]
  22. Oliverio MI, Kim HS, Ito M, Le T, Audoly L, Best CF, Hiller S, Kluckman K, Maeda N, Smithies O, and Coffman TM. Reduced growth, abnormal kidney structure, and type 2 (AT2) angiotensin receptor-mediated blood pressure regulation in mice lacking both AT1A and AT1B receptors. Proc Natl Acad Sci USA 95: 15496–15501, 1998.[Abstract/Free Full Text]
  23. Olson AL, Perlman S, and Robillard JE. Developmental regulation of angiotensinogen gene expression in sheep. Pediatr Res 28: 183–185, 1990.[Abstract]
  24. Robillard JE, Schutte BC, Page WV, Fedderson JA, Porter CG, and Segar JL. Ontogenic changes and regulation of renal angiotensin type 1 receptor gene expression during fetal and newborn life. Pediatr Res 36: 755–762, 1994.[Abstract]
  25. Schütz S, Le Moullec JM, Corvol P, and Gasc JM. Early expression of all the components of the renin-angiotensin system in human development. Am J Pathol 149: 2067–2079, 1996.[Abstract]
  26. Shanmugam S, Corvol P, and Gasc JM. Ontogeny of the two angiotensin II type 1 receptor subtypes in rats. Am J Physiol Endocrinol Metab 267: E828–E836, 1994.[Abstract/Free Full Text]
  27. Tojo A, Tisher CC, and Madsen KM. Angiotensin II regulates H+-ATPase activity in rat cortical collecting duct. Am J Physiol Renal Fluid Electrolyte Physiol 267: F1045–F1051, 1994.[Abstract/Free Full Text]
  28. Tsuchida S, Matsusaka T, Chen X, Okubo S, Niimura F, Nishimura H, Fogo A, Utsunomyia H, Inagami T, and Ichikawa I. Murine double nullizygotes of the angiotensin type 1A and 1B receptor genes duplicate severe abnormal phenotypes of angiotensinogen nullizygotes. J Clin Invest 101: 755–760, 1998.[Abstract/Free Full Text]
  29. Tufro-McReddie A, Harrison JK, Everett AD, and Gomez RA. Ontogeny of type 1 angiotensin II receptor gene expression in the rat. J Clin Invest 91: 530–537, 1993.[ISI][Medline]
  30. Tufro-McReddie A, Romano LM, Harris JM, Ferder L, and Gomez RA. Angiotensin II regulates nephrogenesis and renal vascular development. Am J Physiol Renal Fluid Electrolyte Physiol 269: F110–F115, 1995.[Abstract/Free Full Text]
  31. Weiner ID, New AR, Milton AE, and Tisher CC. Regulation of luminal alkalinization and acidification in the cortical collecting duct by angiotensin II. Am J Physiol Renal Fluid Electrolyte Physiol 269: F730–F738, 1995.[Abstract/Free Full Text]
  32. Yosipiv IV and El-Dahr SS. Activation of angiotensin-generating systems in the developing rat kidney. Hypertension 27: 281–286, 1996.[Abstract/Free Full Text]