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Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana.
Correspondence to Dr. Hiroyuki Kobori, Department of Physiology, Tulane University School of Medicine, 1430 Tulane Ave., SL39, New Orleans, LA 70112-2699. Phone: 504-588-5251; Fax: 504-584-2675; E-mail: hkobori{at}1tulane.edu
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Although chronic administration of subpressor doses of AngII to normal rats produces slowly developing hypertension that is associated with diminished renal renin content and mRNA levels, there is enhancement of renal angiotensin-converting enzyme activity and augmentation of the intrarenal AngII content, which are attributable, in part, to sustained local production of AngII (10,11,12). However, the relative contributions of the renal and hepatic expression of angiotensinogen mRNA to the increased intrarenal AngII content remain unclear. Schunkert et al. (13) demonstrated that AngII infusion (300 to 1000 ng/kg per min, administered subcutaneously) for 3 d increased renal angiotensinogen mRNA levels, whereas Sechi et al. (14) demonstrated that AngII infusion (200 ng/kg per min, administered subcutaneously) for 7 d did not alter the renal expression of angiotensinogen mRNA. In addition, Schunkert et al. (13) and Abe and associates (15,16,17) (using 200 ng/kg per min, administered intravenously for 4 h) demonstrated that AngII-treated rats exhibited increased hepatic angiotensinogen mRNA levels, whereas Sechi et al. (14) demonstrated that AngII infusion did not alter the hepatic expression of angiotensinogen mRNA. Previous studies did not determine the effect of AngII infusion on renal or hepatic angiotensinogen protein levels in AngII-dependent hypertension. This study was performed to examine the changes in renal and hepatic angiotensinogen mRNA and protein levels in AngII-treated rats at a time when intrarenal AngII levels are increased.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Primary Antibody for Angiotensinogen
Sheep polyclonal antibody against purified rat angiotensinogen was produced
and characterized at the University of Queensland
(20,21).
The primary antiserum was diluted 1:4000 for immunohistochemical analyses and
1:5000 for Western blot analyses.
Immunohistochemical Analyses
Five-micron sections of kidneys fixed with Bouin's fixative were
immunostained for angiotensinogen using the immunoperoxidase technique, with a
commercially available kit (Vectastain ABC kit; Vector Laboratories,
Burlingame, CA), as described previously
(19). Sections were
counterstained with hematoxylin and lithium carbonate. The reaction times for
the primary and biotinylated secondary antibodies (Vector Laboratories) were
90 and 30 min, respectively. The specificity of immunostaining was determined
by omission of the primary antibody.
Western Blot Analyses
Proteins were routinely extracted from kidney and liver samples, after
homogenization with protease inhibitors (100 µg/ml phenylmethylsulfonyl
fluoride, 1 µg/ml leupeptin, 1 µg/ml aprotinin, and 2 mM
ethylenediaminetetraacetate, final concentrations in lysis buffer), and
quantified as described previously in detail
(2). Plasma (5 µg), kidney
(25 µg), or liver (25 µg) protein samples were electrophoretically
separated on 3 to 8% Tris-glycine stacking gels at 125 V for 2.5 h, in
duplicate. One gel was stained with 0.1% Coomassie Blue R250 (Sigma Chemical
Co., St. Louis, MO) for observation of the protein bands, to confirm equal
loading of protein samples. The proteins from the second gel were
electrophoretically transferred to a nitrocellulose membrane (Bio-Rad
Laboratories, Hercules, CA) for 90 min at 25 V (XCell II Mini-Cell; Novex, San
Diego, CA). The efficiency of transfer was confirmed by staining the depleted
gel with Coomassie Blue. Molecular mass markers (10- to 250-kD rainbow
markers; Amersham Pharmacia Biotech, Piscataway, NJ) were used to determine
approximate molecular masses. Western blot analyses were performed as
described previously
(2,19).
Blots were incubated with the primary antibody for 3 h, washed, incubated with
horseradish peroxidase-conjugated secondary antibody (donkey anti-sheep IgG,
1:30,000; Sigma) for 1 h, and washed again. Detection was accomplished using
enhanced chemiluminescence Western blotting (ECL system; Amersham Pharmacia
Biotech), and the blots were exposed to x-ray film (Hyperfilm-ECL; Amersham
Pharmacia Biotech). The autoradiographic films were scanned using digital
imaging and analysis systems (Alpha Innotech, San Leandro, CA), to obtain
integrated densitometric values (IDV). IDV were normalized using the average
values for the sham-treated group. To determine the degree of glycosylation of
plasma angiotensinogen, 5 µg of plasma protein was incubated with peptide
N-glycosidase F (4000 U; New England Bio-Labs, Beverly, MA) overnight
at 37°C. As a positive control, a single plasma sample was obtained from a
rat 24 h after bilateral nephrectomy.
Angiotensinogen protein levels were measured in the linear range of the detection method. Protein samples of 1.25 to 10, 6.25 to 100, and 6.25 to 100 µg/lane resulted in linear increases in the densitometric signals for plasma, kidney, and liver, respectively.
Isolation of Total RNA
Total RNA was extracted from kidney and liver (tissue weight, 150 to 200
mg) using a RNeasy midi kit (Qiagen, Chatsworth, CA), according to the
protocol provided by the manufacturer. The extracted RNA was suspended in
ribonuclease-free water and was quantified by measuring the absorbance at 260
nm. The integrity of the purified RNA collected by this method was confirmed
by observation of the 28S and 18S rRNA bands after agarose gel
electrophoresis.
Reverse Transcription of RNA
Total RNA from each kidney or liver sample was reverse-transcribed using
the SuperScript preamplification system for first-strand cDNA synthesis (Life
Technologies BRL, Gaithersburg, MD). Each sample contained 2.5 µg of total
RNA, 50 ng of random hexamers, 2 µl of 10 x buffer, 50 nmol of
MgCl2, 10 nmol of each dNTP (dATP, dTTP, dGTP, and dCTP), 200 nmol
of dithiothreitol, and 200 U of SuperScript II reverse transcriptase, in a
final volume of 20 µl. After preincubation at 25°C for 10 min, the
samples were incubated at 42°C for 50 min and then heated at 70°C for
15 min, to terminate the reaction. To remove the remaining RNA, 2 U of
Escherichia coli RNase H was added to the samples, which were then
incubated at 37°C for 20 min.
Preparation of Primers
Oligonucleotide primers were designed from the published cDNA sequences of
angiotensinogen (22) and
glyceraldehyde-3-phosphate dehydrogenase (GAPDH)
(23). GAPDH was used as an
internal standard. The sequences of the angiotensinogen primers were as
follows: sense, 5'-TTGTTGAGAGCTTGGGTCCCTTCA-3' (exon 2, bases +638
to +661); antisense, 5'-CAGACACTGAGGTGCTGTTGTCCA-3' (exon 3, bases
+901 to +878). The sequences of the GAPDH primers were as follows: sense,
5'-TCCCTCAAGATTGTCAGCAA-3' (bases +421 to +440); antisense,
5'-AGATCCACAACGGATACATT-3' (bases +728 to +709). The expected
sizes of the amplified angiotensinogen and GAPDH PCR products were 264 and 308
bp, respectively.
Semiquantitative PCR
Semiquantitative reverse transcription-PCR (RT-PCR) was performed as
described previously (24).
Each reaction contained 0.25 to 4 µl of the RT mixture, 2.5 µl of 10
x buffer, 37.5 nmol of MgCl2, 5 nmol of each dNTP, 5 pmol of
each sense and antisense primer for angiotensinogen or GAPDH, and 0.625 U of
Taq DNA polymerase (Life Technologies BRL), in a final volume of 25
µl. PCR was performed in a thermocycler (DNA thermal cycler 480; Perkin
Elmer, Norwalk, CT) for 15 to 40 cycles, using a 45-s denaturation step at
94°C, a 30-s annealing step at 52°C, and a 90-s extension step at
72°C, with a final 10-min extension step at 72°C. After completion of
RT-PCR, PCR products for angiotensinogen and GAPDH from each animal were
combined and electrophoresed on a 3% agarose gel for 1.5 h at 200 V. The gel
was stained with ethidium bromide for 30 min and scanned with ultraviolet
illumination, using digital imaging and analysis. No PCR products were
detected in the absence of reverse transcriptase. Because GAPDH mRNA levels
did not differ between groups, angiotensinogen mRNA expression was evaluated
as the angiotensinogen IDV/GAPDH IDV ratio.
The relationship between the amount of total RNA template (31.25 to 500 ng) and RT-PCR products was evaluated. A linear relationship was observed in the range of 62.5 to 500 ng for renal angiotensinogen and 62.5 to 250 ng for renal GAPDH at 28 cycles and in the range of 31.25 to 125 ng for hepatic angiotensinogen and 31.25 to 62.5 ng for hepatic GAPDH at 25 cycles.
The relationship between PCR cycle number (15 to 40 cycles) and RT-PCR products was also evaluated. A linear relationship between the number of PCR cycles and the amount of PCR product was observed from 23 to 33 cycles for renal angiotensinogen and from 23 to 28 cycles for renal GAPDH with 125 ng of total renal RNA and from 23 to 28 cycles for hepatic angiotensinogen and from 18 to 25 cycles for hepatic GAPDH with 62.5 ng of total hepatic RNA. On the basis of these data, the optimal total RNA template amounts and PCR cycle numbers were as follows: 125 ng and 33 cycles for kidney angiotensinogen, 125 ng and 25 cycles for kidney GAPDH, 62.5 ng and 28 cycles for liver angiotensinogen, and 62.5 ng and 25 cycles for liver GAPDH.
The PCR products were dideoxy-sequenced (Research Genetics Genome Center, Huntsville, AL), using an ABI PRISM cycle sequencing kit (Perkin Elmer), to confirm that they were angiotensinogen and GAPDH. The sequences obtained were identical to those previously reported (22,23).
Statistical Analyses
Results are expressed as mean ± SEM. The data were analyzed between
groups using the unpaired t test. Statistical significance was
defined at a value of P < 0.05.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Systolic BP values for the two groups were similar before implantation of the osmotic minipumps (AngII, 117 ± 2 mmHg; sham, 116 ± 2 mmHg). On days 3, 6, and 12 of infusion, systolic BP was significantly elevated, to 141 ± 1, 159 ± 3, and 184 ± 3 mmHg, respectively, for the AngII-treated rats, compared with sham-treated rats (116 ± 3, 114 ± 3, and 125 ± 1 mmHg, respectively).
Plasma renin activity was markedly suppressed in the AngII-treated rats, compared with the sham-treated rats [0.2 ± 0.1 ng AngI/ml per h (n = 8) versus 5.3 ± 1.2 ng AngI/ml per h (n = 7)]. The kidney AngII content was significantly increased in AngII-treated rats, compared with sham-treated rats [273 ± 29 fmol/g kidney (n = 8) versus 99 ± 18 fmol/g kidney (n = 4)].
Immunohistochemical Detection of Renal Angiotensinogen
Immunohistochemical detection of angiotensinogen in the renal cortex of
normal rats was performed to determine the intrarenal localization of
angiotensinogen and to confirm that the protein detected by Western blot
analysis was consistent with the known proximal tubular localization.
Figure 1A demonstrates
prominent proximal tubular immunolocalization of angiotensinogen protein.
Distal tubules exhibited negative results.
Figure 1B demonstrates strong
positive immunostaining in proximal convoluted tubules and weak positive
staining in glomerular endothelial cells; however, there was no staining in
distal tubules or the renal vasculature. There was no staining in collecting
ducts; however, faint positive immunostaining was detected in vasa recta
bundles (data not shown). There was no positive immunostaining when the
primary antibody was omitted (Figure
1C). Therefore, Western blot analysis of angiotensinogen contents
in total kidney protein extracts should reflect changes in proximal tubule
angiotensinogen protein contents.
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Western Blot Analysis of Plasma Angiotensinogen
Western blot analysis of plasma protein using the angiotensinogen-specific
polyclonal antibody demonstrated two specific bands, at 52 and 64 kD
(Figure 2A, left lane). It was
previously demonstrated that preabsorption of the primary antibody with pure
angiotensinogen or replacement of the angiotensinogen-specific antibody with
preimmune serum abolished both bands
(20,21).
Incubation of plasma with peptide N-glycosidase F demonstrated that
the two bands were shifted to one band at approximately 50 kD
(Figure 2A, right lane),
suggesting the presence of highly glycosylated and slightly glycosylated forms
of circulating angiotensinogen. Densitometric analysis of plasma protein
obtained 24 h after bilateral nephrectomy
(Figure 2B, lane
PNx) indicated that levels of the 64-kD angiotensinogen protein
were elevated by approximately 50%, compared with values for sham-treated
control animals (Figure 2B,
lane PC). Levels of the 52-kD angiotensinogen protein were not
altered. Figure 2C shows a
representative Western blot of plasma (5 µg) angiotensinogen from
AngII-treated and sham-treated rats. Densitometric analysis of the
immunoreactive bands indicated that AngII infusion did not alter plasma
angiotensinogen protein levels (densitometric value/average control value
ratios of 0.95 ± 0.08 versus 1.00 ± 0.06 for the 64-kD
protein and 1.04 ± 0.07 versus 1.00 ± 0.08 for the
52-kD protein) (Figure 2D).
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Western Blot Analysis of Kidney and Liver Angiotensinogen
Western blot analysis of kidney protein (25 µg) using a polyclonal
anti-angiotensinogen antibody demonstrated one specific immunoreactive band,
at 52 kD (Figure 2B, lane K),
whereas liver protein (25 µg) presented bands at 52 and 64 kD
(Figure 2B, lane L).
Densitometric analysis of the immunoreactive bands demonstrated that total
angiotensinogen protein contents (52 and 64 kD) in the liver were
approximately 2.4-fold higher than those in the kidney.
Figure 3A shows a representative Western blot of renal angiotensinogen protein from AngII-treated and sham-treated rats. Renal angiotensinogen protein levels were not significantly increased by AngII infusion, although an upward trend was observed (densitometric ratios of 1.23 ± 0.14 versus 1.00 ± 0.08, P = 0.161) (Figure 3B).
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Figure 3C shows a representative Western blot of hepatic angiotensinogen protein from AngII-treated and sham-treated rats. AngII infusion increased hepatic levels of the 64-kD angiotensinogen protein almost fourfold (densitometric ratios of 3.79 ± 1.16 versus 1.00 ± 0.35, P = 0.039) (Figure 3D); however, hepatic levels of the 52-kD angiotensinogen protein were not altered (densitometric ratios of 1.21 ± 0.21 versus 1.00 ± 0.12, P = 0.409).
Expression of Renal and Hepatic Angiotensinogen mRNA
Representative RT-PCR results for the renal expression of angiotensinogen
mRNA in control and AngII-treated rats are depicted in
Figure 4A. Semiquantitative
analysis indicated that AngII infusion significantly increased renal
angiotensinogen mRNA expression, by 42% (densitometric value/GAPDH mRNA value
ratios of 0.82 ± 0.11 versus 0.58 ± 0.04, P =
0.038) (Figure 4B).
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Representative RT-PCR results for the hepatic expression of angiotensinogen mRNA in control and AngII-treated rats are depicted in Figure 4C. Semiquantitative analysis indicated that AngII infusion significantly increased hepatic angiotensinogen mRNA expression, by 78% (densitometric value/GAPDH mRNA value ratios of 2.34 ± 0.07 versus 1.32 ± 0.15, P = 0.0001) (Figure 4D).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Angiotensinogen is a moderately abundant glycoprotein that is the precursor to the angiotensin peptides and is the only known naturally occurring renin substrate (30). The mature form of angiotensinogen consists of 453 amino acids (22,31), and its calculated molecular mass is 50 kD. Angiotensinogen contains two potential sites for N-linked glycosylation (Asn-X-Ser/Thr-X, amino acid positions 295 and 319), and different glycosylation patterns are apparently responsible for size variations in the circulating protein (30). When our deglycosylation study results are considered, we can conclude that the immunoreactive band at 64 kD is a highly glycosylated form and that at 52 kD is a slightly glycosylated form. It is interesting to note that the increase in plasma levels of the highly glycosylated form of angiotensinogen protein after bilateral nephrectomy is consistent with the increased levels of 64-kD angiotensinogen protein observed in the liver after chronic AngII infusion. However, the predominant form in the kidney is the lower-molecular mass form, which suggests a dissociation between the circulatory and intrarenal angiotensinogen forms. The similarity of the distributions of the 52- and 64-kD angiotensinogen proteins observed in liver and plasma suggests that circulating plasma angiotensinogen originates mainly from angiotensinogen synthesized in the liver. The finding that almost all of the renal angiotensinogen was of the slightly glycosylated form suggests that renal angiotensinogen may be primarily of local origin or may be altered to that form during uptake into renal cells. Another interpretation for the similarity of the distribution patterns of the 52- and 64-kD angiotensinogen proteins in liver and plasma is that the distribution patterns could reflect similar levels of glycosylation and deglycosylation in those tissues. Kidney angiotensinogen could originate from the liver and be proteolytically processed differently after it reaches the kidney; alternatively, the kidney may produce only the slightly glycosylated form of angiotensinogen.
It is interesting to note that the relative amounts of the glycosylated forms of liver angiotensinogen were altered by AngII infusion, with the 64-kD form exhibiting a 3.8-fold increase. Tewksbury and Dart (32) reported that increases in high-molecular weight angiotensinogen, but not low molecular-weight angiotensinogen, were associated with pregnancy-induced hypertension in woman. Tewksbury and Tryon (33) also reported that high-molecular weight angiotensinogen was a better substrate for renin, compared with low-molecular weight angiotensinogen. In general, glycosylated proteins are more stable than nonglycosylated proteins (34). In our study, glycosylation of liver angiotensinogen might have modified its biochemical properties to promote the production of AngII, despite marked suppression of renin activity.
In agreement with previous findings, chronic low-dose infusion of AngII produced significant elevations in systolic BP (2,11,12,18), reductions in plasma renin activity (2,10,11,12), and increases in renal AngII contents (10,11,12,18). After 13 d of infusion, we observed that plasma angiotensinogen protein levels (52 and 64 kD) were maintained under conditions of chronically increased AngII levels. Although renal angiotensinogen protein levels were not significantly increased, hepatic levels of the 64-kD angiotensinogen protein were significantly elevated. Furthermore, renal and hepatic angiotensinogen mRNA levels were significantly elevated (by 42 and 78%, respectively) in AngII-treated rats, compared with sham-treated rats.
Schunkert et al. (13) demonstrated that AngII infusions of 300 ng/kg per min (approximately 80 ng/min) did not alter plasma angiotensinogen concentrations in male Sprague-Dawley rats. Gahnem et al. (35) presented evidence that there was no significant tonic stimulatory effect of AngII on plasma angiotensinogen levels in stroke-prone spontaneously hypertensive rats or Dahl salt-sensitive rats. In this study, we did not observe changes in the levels of either form of plasma angiotensinogen protein in response to chronic AngII infusions. In rats, plasma angiotensinogen concentrations are quite high, relative to circulating angiotensin peptide levels (11,36), and small variations in angiotensin peptide production rates may not significantly affect circulating angiotensinogen concentrations. Furthermore, in this study we used an antibody that recognizes both angiotensinogen and des-AngI angiotensinogen, so that the total amount of angiotensinogen would be reflected in Western blot analyses (C. Sernia, personal communication).
Ingelfinger et al. (9) recently demonstrated positive AngII feedback on angiotensinogen and AngII receptor mRNA expression in an immortalized rat proximal tubular cell line. However, the results of in vivo studies of the contribution of increased renal expression of angiotensinogen mRNA to the hypertensinogenic effects of AngII have remained inconclusive (13,14). Our results for AngII-treated rats demonstrated a 42% increase in renal angiotensinogen mRNA levels associated with increased intrarenal AngII contents. These findings are consistent with the concept that elevated circulating and intrarenal AngII concentrations lead to increased angiotensinogen mRNA levels, which may provide an enhanced angiotensin peptide-generating capability for the kidney. However, the renal angiotensinogen mRNA data are not complemented by elevated angiotensinogen protein levels, suggesting only maintained and not increased substrate availability. Zou et al. (11) assessed kidney angiotensinogen levels by measuring AngI generation after incubation with excess renin and similarly demonstrated sustained angiotensinogen levels in AngII-dependent hypertension. The concentration of angiotensinogen is close to the Km for renin (3); therefore, changes in either substrate or enzyme levels could affect angiotensin production. Increases in angiotensinogen levels could thus help maintain AngI levels in the presence of decreased renin levels. The importance of angiotensinogen production levels was also shown by Smithies and Kim (37), who demonstrated a linear relationship between angiotensinogen gene copy number and BP in transgenic mice. Whether angiotensinogen levels are sustained or slightly increased, the significant point of pathophysiologic relevance is that they are not decreased, despite the elevations in circulating and intrarenal AngII levels and arterial BP. These sustained angiotensinogen levels are presumably responsible for continued intrarenal production of AngI. These data help explain the results of Zou et al. (11), which indicated a dissociation between the plasma and intrarenal AngI levels in AngII-treated rats. Chronic AngII infusions markedly suppressed renin levels and predictably reduced circulating AngI concentrations to barely detectable levels (11). Nevertheless, kidney AngI contents were not significantly reduced in the AngII-treated rats, demonstrating a sustained AngI-generating capacity in the kidney that may contribute importantly to the increased intrarenal AngII levels (11). Our data are consistent with the recent findings of Bohlender et al. (38), which demonstrated that transgenic offspring of rats that overexpressed both the human angiotensinogen and human renin genes exhibited elevated plasma renin activities and concentrations and elevated BP, although the human and rat renin genes were downregulated. Those authors concluded that increased angiotensinogen concentrations decreased the renin metabolic clearance rate, resulting in increased AngI levels independent of renin secretion and AngII-mediated feedback.
Our results also demonstrated marked stimulation of hepatic angiotensinogen
mRNA levels in AngII-treated rats. Klett et al.
(8) presented evidence that
AngII enhances hepatic angiotensinogen synthesis by inhibiting the degradation
of angiotensinogen mRNA in hepatocytes. Brasier and Li
(3,39)
suggested that angiotensinogen gene activation by AngII is mediated by the
nuclear factor-
B p65 transcription factor in hepatocytes.
However, Corvol and associates
(40,41,42)
demonstrated that exposure of human hepatoma cells to the AngII agonist
Sar1-AngII caused a dose-dependent decrease in angiotensinogen
production and that the cellular mechanism involved a pertussis
toxin-sensitive G protein. In vivo studies by Schunkert et
al. (13) and Abe and
associates
(15,16,17)
demonstrated that AngII infusion increased hepatic angiotensinogen mRNA
levels, whereas Sechi et al.
(14) found that AngII infusion
did not alter the hepatic expression of angiotensinogen mRNA. Although
substantial variability in the magnitude of the responses was observed, our
data also demonstrated a significant increase in hepatic angiotensinogen
protein levels in rats treated with AngII for 13 d.
In our study, renal angiotensinogen mRNA expression was increased significantly with AngII infusion; renal angiotensinogen protein levels were not increased significantly with AngII infusion, although an upward trend was noted. One possible explanation for the apparent discrepancy between angiotensinogen mRNA and protein levels may be related to the differences in the amplification and sensitivity of the methods used to detect angiotensinogen mRNA (RT-PCR) and angiotensinogen protein (Western blotting). Furthermore, because angiotensinogen is constitutively secreted, it may be more difficult to demonstrate changes in steady-state tissue levels. It is also possible that the control rats might already have been experiencing substantial stimulation of angiotensinogen production, making it more difficult to demonstrate an additional increase in angiotensinogen levels with AngII infusion.
On the basis of these results and our previous results, we conclude that increased angiotensinogen mRNA levels contribute to the maintenance of intrarenal endogenous AngII levels observed in AngII-treated hypertensive rats, by sustaining locally formed AngI and AngII. Because renal renin synthesis is markedly suppressed, increased angiotensinogen production may be necessary to simply sustain intrarenal AngI and AngII production. However, activation of hepatic angiotensinogen synthesis, which helps maintain endogenous production of circulating AngII in the presence of continuous exogenous infusion of AngII, may also contribute to the elevated intrarenal AngII levels.
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M. C. Prieto-Carrasquero, H. Kobori, Y. Ozawa, A. Gutierrez, D. Seth, and L. G. Navar AT1 receptor-mediated enhancement of collecting duct renin in angiotensin II-dependent hypertensive rats Am J Physiol Renal Physiol, September 1, 2005; 289(3): F632 - F637. [Abstract] [Full Text] [PDF]
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 H. Kobori, Y. Ozawa, Y. Suzaki, and A. Nishiyama Enhanced Intrarenal Angiotensinogen Contributes to Early Renal Injury in Spontaneously Hypertensive Rats J. Am. Soc. Nephrol., July 1, 2005; 16(7): 2073 - 2080. [Abstract] [Full Text] [PDF]
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 B. C Cholewa and D. L Mattson Influence of elevated renin substrate on angiotensin II and arterial blood pressure in conscious mice Exp Physiol, July 1, 2005; 90(4): 607 - 612. [Abstract] [Full Text] [PDF]
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M. C. Prieto-Carrasquero, L. M. Harrison-Bernard, H. Kobori, Y. Ozawa, K. S. Hering-Smith, L. L. Hamm, and L. G. Navar Enhancement of Collecting Duct Renin in Angiotensin II-Dependent Hypertensive Rats Hypertension, August 1, 2004; 44(2): 223 - 229. [Abstract] [Full Text] [PDF]
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X174 RF DNA).
*P < 0.05.