From the Research Institute of Angiocardiology and Cardiovascular Clinic,
Kyushu University Faculty of Medicine, Fukuoka, Japan.
Correspondence to Toshihiro Ichiki, MD, PhD, Research Institute of Angiocardiology and Cardiovascular Clinic, Kyushu University Faculty of Medicine, 3–1-1, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Endothelium plays an important role in the homeostasis
of vascular tone by producing endothelium-derived
substances.13 14 15 An important
endothelium-derived relaxing factor has been identified
to be nitric oxide (NO) or a related
compound.16 17 In addition, NO inhibits
platelet aggregation and leukocyte adhesion, which suggests that NO
may have a negative effect on the growth and/or proliferation of blood
vessels.13 15 18 19 20 21 22 Several reports have shown
that NO antagonizes the biological function of Ang II. NO inhibits Ang
II–induced migration of vascular smooth muscle
cells.23 NO also prevents Ang II–induced
[3H]thymidine incorporation and cell
proliferation in rat mesenteric arteriolar smooth muscle
cells.24
We25 26 27 and other
investigators26 27 28 29 30 31 have recently reported that
long-term blockade of NO synthesis with chronic administration of
N
Drugs and Materials
Animal Preparation and Tissue Preparation
After 1 week of treatment, systolic blood pressure (SBP;
tail-cuff method) and body weight were measured. All rats were
anesthetized with an injection of sodium pentobarbital (50
mg/kg IP) and killed by exsanguination. Blood was collected into
prechilled tubes containing EDTA disodium salt for the measurements of
plasma renin activity (PRA) and plasma aldosterone
concentration (PAC). Blood was collected in plain tubes for the
measurement of serum ACE activity, serum corticosterone concentration
(SCC), and serum potassium and sodium concentrations. The plasma and
serum were separated by centrifugation at 3000 rpm for
20 minutes at 4°C and stored at -80°C until measurement of PRA,
PAC, serum ACE activity, SCC, and serum potassium and sodium
concentrations. PRA was measured as the rate of angiotensin
I generation from angiotensinogen, determined with a
radioimmunoassay (SRL Co Ltd). PAC was also determined with a
radioimmunoassay method (SRL Co Ltd). Serum ACE activities were
measured using a fluorometric assay described by Cheung and
Cushman35 and Hayashi et al.36 Serum ACE
activity was calculated as nanomoles His-Leu generated per
milliliter of serum per hour. SCC was also determined with a
radioimmunoassay method (SRL Co Ltd). Left and right adrenal glands
were removed, frozen in liquid nitrogen, and stored at -80°C. Both
adrenal glands from 6 rats in each group were pooled and used for RNA
extraction for Northern blot analysis, and adrenal glands from
another 4 rats were used for the radioligand binding
assay.
cDNA Probes for Northern Blot Analysis
RNA Extraction and Northern Blots
Ang II Receptor Binding Assay
Statistical Analysis
SBP in the L group increased, but drug treatment did not change SBP in
the C and L+B groups. After treatment, heart rate in the L group was
less than in the C group but was comparable to that in the L+B
group.
AT1A, AT1B, and AT2 mRNA Levels
in Adrenal Gland
Ligand Binding
Figure 5
PAC, PRA, Serum ACE Activity, Serum Potassium Concentration,
and SCC
As shown previously,34 SBP in the L group was
increased after 1 week of treatment (204±9 mm Hg) compared with
that in the C group (140±5 mm Hg). The mRNA levels of
AT1A-R and AT1B-R in the L
group were increased 1.7-fold and 1.8-fold, respectively. Although
bunazosin reduced blood pressure to a level comparable to that in the C
group, it did not affect the mRNA level and the number of
AT1-R. These results suggest that the
upregulation of AT1-R (both mRNA level and
receptor number) by L-NAME was independent of blood pressure elevation.
Although bunazosin reduced blood pressure to the control level, heart
rate in the L+B groups remained decreased. Although the mechanism is
not clear, it may suggest that bradycardia induced by L-NAME is not due
to an elevation of blood pressure but to inhibition of NO itself.
Our results are consistent with those of Cahill et
al.40 They reported that NO-generating drugs
decreased Ang II receptors in cultured rat vascular smooth muscle
cells. However, the precise mechanism of the downregulation of
AT1-R by NO donor or the upregulation of
AT1-R by L-NAME is unknown.
Differential regulation of the transcription of
AT1A-R and AT1B-R gene has
been reported.37 41 The
AT1A-R mRNA levels in the kidney are
significantly increased, whereas renal AT1B-R
mRNA levels are markedly decreased by low dietary sodium
intake.37 The AT1B-R mRNA
levels in the adrenal gland are reduced by treatment with the
AT1-specific antagonist TCV 116, but
AT1A-R mRNA levels are unchanged. In this study,
both AT1A-R and AT1B-R mRNA
levels were upregulated by L-NAME treatment. Therefore, some stimuli
upregulate the expression of both receptors, whereas others
differentially affect AT1A-R and
AT1B-R gene transcription. The gene expression of
AT2-R is modulated by many
cytokines,42 growth
factors,43 and protein kinase
C.44 In the adrenal gland, blockade of NO
synthesis did not affect the mRNA level and the receptor number of
AT2-R.
Ang II is a strong secretagogue of aldosterone from adrenal
cortex and also important for basal aldosterone
release.20 Takemoto et al34
reported that the inhibition of NO synthesis by L-NAME for 8 weeks
increased PRA and serum ACE. In this study, we showed that L-NAME
administration for 1 week increased PAC but not PRA or serum ACE
activity. Bunazosin did not affect PAC. These findings suggest that
increased PAC induced by L-NAME was not dependent on the systemic RAS
or blood pressure. Because not only Ang II but also
corticotropin or serum potassium concentration affect
aldosterone secretion, we examined SCC and serum potassium
concentration in this study. SCC was slightly increased in the L and
L+B groups, but there was no significant statistical difference among 3
groups, and there was no correlation between PAC and SCC. Therefore, it
suggests that corticotropin level is not significantly different among
3 groups. In this study, PAC was increased in L and L+B groups, but
serum potassium was not increased in these groups. Some compensatory
mechanism may work, but the mechanism is not clear. Because PRA, serum
ACE activity, and SCC did not change, it is likely that increased PAC
caused by L-NAME treatment resulted from the increase in the
AT1-R in the adrenal glands. However, we did not
exclude the possibility that the local RAS in the adrenal gland was
activated by the blockade of NO synthesis. Our results differed
from those of Simmons and Freeman,45 which
suggested that the aldosterone secretion rate was
attenuated in rats treated with L-NAME or
N
Recently, many studies have reported that aldosterone is
involved in cardiac hypertrophy and fibrosis, which,
together with myocardial cell death, may contribute to progressive
myocardial remodeling.46 47 48 49 50 51 We have previously
shown that chronic treatment with L-NAME in rats caused vascular
thickening and myocardial hypertrophy with perivascular
fibrosis.34 Therefore, the results of this study
suggest the possibility that aldosterone may play a role in
perivascular and myocardial fibrosis in these models. However, it is
necessary to confirm whether aldosterone
antagonist is effective in preventing or attenuating the
myocardial remodeling in L-NAME–treated animals.
Aldosterone stimulates sodium uptake in the distal tubule
of the kidney, resulting in water retention. Therefore, increased PAC
may play a role in maintaining high blood pressure in L-NAME–treated
rats. Under normal conditions, NO may inhibit aldosterone
secretion by suppressing AT1-R expression.
Our finding that NO modulates the Ang II receptor may have an important
implication for the understanding of the role of these molecules in the
progression of atherosclerosis. In the rodent model,
ACE inhibitor prevents neointimal formation
induced by balloon injury. These data suggest that Ang II plays an
important role in the growth and proliferation of vascular smooth
muscle cells and remodeling of the vascular wall. Our data clearly show
that blockade of NO enhanced the expression of Ang II receptor and its
biological function in the adrenal gland independent of systemic blood
pressure or the systemic RAS. Therefore, it is possible that vascular
thickening and perivascular fibrosis observed in rats with chronic
treatment of L-NAME are due to upregulation of Ang II receptor in
vascular wall. Studies examining the Ang II receptor in vascular wall
are in progress and will address the role of Ang II receptor in the
pathogenesis of structural changes of coronary artery in
L-NAME–treated rats.
In conclusion, these data demonstrate that the inhibition of NO
synthesis by L-NAME increased both AT1A-R and
AT1B-R mRNA expression and
AT1-R number in the rat adrenal gland independent
of blood pressure and the systemic RAS. AT2-R
mRNA expression and AT2-R number did not change
with L-NAME, and the inhibition of NO synthesis increased PAC but not
PRA or serum ACE activity. Our findings suggest that inhibition of NO
synthesis causes AT1-R upregulation in the
adrenal gland and increases PAC. Therefore, L-NAME–induced
hypertension and myocardial fibrosis may be partially due to the
elevation of PAC induced by increased AT1-R in
the adrenal gland.
Received March 23, 1998;
first decision April 2, 1998;
accepted April 13, 1998.
© 1998 American Heart Association, Inc.
Scientific Contributions
Regulation of Angiotensin II Receptor Expression by Nitric Oxide in Rat Adrenal Gland
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
Abstract—We recently reported that
administration of
N
-nitro-L-arginine methyl
ester (L-NAME), an inhibitor of nitric oxide (NO)
production, activates the vascular and cardiac
renin-angiotensin systems and causes vascular thickening
and myocardial hypertrophy in rats with perivascular and
myocardial fibrosis. It has been reported that aldosterone
may contribute to the development of cardiac fibrosis, but it is not
known whether inhibition of NO synthesis affects
angiotensin II (Ang II) receptor gene expression and
aldosterone secretion. The aim of this study was to
investigate the effect of NO inhibition on the expression of Ang II
receptors in the adrenal gland and on aldosterone secretion
in rats. Wistar King A rats received normal water, L-NAME alone (1
mg/mL in the drinking water), or L-NAME and the 
1-adrenergic
receptor blocker bunazosin (0.1 mg/mL in the drinking water) for 1
week. After 1 week of treatment with L-NAME, systolic blood
pressure, plasma aldosterone concentration (PAC), and mRNA
level and number of Ang II type 1 receptor (AT1-R)
were increased. Plasma renin activity, serum
angiotensin-converting enzyme activity, and the number of
AT2-R were unchanged. Although addition of bunazosin to
L-NAME restored systolic blood pressure to the control level,
PAC and AT1-R numbers remained significantly higher than
those of control level. These results suggest that the increased
AT1-R number and PAC induced by the inhibition of NO
synthesis were independent of blood pressure and systemic
renin-angiotensin system. Therefore, hypertension and
myocardial fibrosis induced by NO blockade may be due in part to an
elevation of PAC caused by increased AT1-R in the
adrenal gland.
Key Words: nitric oxide • receptors, angiotensin • plasma aldosterone concentration • L-NAME • adrenal gland
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
Angiotensin II (Ang
II) has a strong vasopressor effect and also regulates electrolyte
balance and drinking behavior. Its actions are mediated by specific
receptors located on various target organs, including the adrenal
gland, kidney, uterus, brain, and arterioles.1 2
Recently, it was discovered that Ang II receptors are
heterogeneous and could be classified into at least 2
subtypes: Ang II type 1 receptor (AT1-R) and type
2 receptor (AT2-R). It is generally accepted that
most of the biological effects of Ang II known to date are mediated by
the AT1-R. AT1-R
antagonists reduce blood pressure in renal hypertensive
rats and inhibit Ang II–induced aldosterone release from
adrenal cortex, epinephrine secretion, and water
drinking.3 4 5 6 7 Recent molecular cloning of the
AT1-R in rats revealed the existence of 2
subtypes, ie, AT1A-R and
AT1B-R.8 9 10 11 12 The
AT2-R is abundantly expressed in adrenal medulla,
but its function has not been identified. -nitro-L-arginine methyl
ester (L-NAME) caused systemic arterial hypertension,
microvascular structural changes (medial thickening and perivascular
fibrosis), and myocardial hypertrophy in rats and pigs.
L-NAME–induced microvascular structural changes were prevented by
angiotensin-converting enzyme (ACE) inhibition and Ang II
receptor antagonism,32 33 34 suggesting that the
renin-angiotensin system (RAS) is activated by
inhibition of NO. However, it has not been determined whether
inhibition of NO synthesis modulates Ang II receptor expression and
aldosterone secretion in the adrenal gland. In the
present study, we investigated the regulation of adrenal Ang II
receptor expression and plasma aldosterone concentration
(PAC) in rats treated with L-NAME.
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
The following protocols were reviewed and approved by the
Committee of the Ethics on Animal Experiment in the Faculty of
Medicine, Kyushu University, and met the requirements of the Law (No.
105) and Notification (No. 6) of the Government.
We used L-NAME (Sigma Chemical Co), bunazosin (Esai
Pharmaceutical Co), CV11974 (Takeda Pharmaceutical Co), PD123319
(Warner-Lambert Co), and [32P]-dCTP and
[125I]-Sar,1Ile8-Ang
II (New England Nuclear).
Eight-week-old male Wistar King A (WKA) rats were obtained from
an established colony at the Animal Research Institute of Kyushu
University Faculty of Medicine. Three groups of rats were studied; the
first group (C group, n=10) received normal drinking water, the second
(L group, n=10) received L-NAME in drinking water (1 g/L), and the
third (L+B group, n=10) received L-NAME and the 1-adrenergic blocker
bunazosin (0.1 g/L) in the drinking water. The daily intake of L-NAME
was approximately 100 mg · kg-1 ·
d-1 in the L group. All rats were fed with
normal chow and were housed in a viral-antigen–free facility for 1
week. All hemodynamic and biochemical studies were
performed after 1 week of treatment.
The cDNA probes were prepared as described
previously.37 To obtain a rat
AT1A-R–specific probe, total RNA from rat kidney
was reverse transcribed (Ready-To-Go T-Primed First-Strand kit,
Pharmacia Biotech AB), and the resultant cDNA was amplified by
polymerase chain reaction (PCR) with the following
primers38 : sense primer
5'-TGGCTTACGACCAAAGGACCA-3' and antisense primer
5'-CAAAGGGAGACTGATGAGATTG-3'. The
AT1B-R–specific probe was prepared in the same
way, except that total RNA from rat adrenal gland was used. A noncoding
fragment (395 bp; +1246 to +1641) was used as a template for making
cDNA probes.8 PCR was carried out by 25 cycles of
denaturation at 95°C for 60 seconds, annealing at 60°C for 60
seconds, and polymerization at 72°C for 60 seconds. The 379-bp
products for AT1A and 395-bp PCR products
for AT1B were subcloned into the pBluescript II
KS(+) vector (Stratagene). The specificity of the
AT1A-R and the AT1B-R
probes was confirmed by a lack of cross-hybridization between
AT1A-R and AT1B-R cDNAs.
The cDNA probe for AT2 was provided by Dr Tadashi
Inagami, Vanderbilt University, Nashville, Tenn.
Total RNA was extracted by the guanidine
thiocyanate-phenol-chloroform extraction method (Isogen; Wako Pure
Chemical Ltd). Total RNA (20 µg) was electrophoresed in a 1% agarose
formaldehyde gel and transferred to a nylon membrane
(Hybond-N+, Amersham Co). After prehybridization
for 2 hours at 42°C in a hybridization buffer containing 50%
formamide, 5x Denhardt's solution, 5x SSC (1x SSC is made up of
150 mmol/L NaCl and 15 mmol/L Na citrate), 0.5% SDS, and 1
g/L heat-denatured salmon sperm DNA, the membrane was hybridized with
[32P]-labeled probe in the same hybridization
buffer for 20 hours at 42°C and washed twice in 2x SSC/1.0% SDS for
30 minutes at 55°C. Blots were exposed to XAR-5 x-ray film (Eastman
Kodak) at -70°C. The membrane was stripped by boiling in 0.1% SDS
solution for 5 minutes and rehybridized to a
[32P]-labeled probe for GAPDH cDNA to obtain a
reference for the amount of applied RNA. Autoradiographic
signals were scanned by a densitometer (Mac Scope, Mitani Co Ltd).
Relative gene expression was expressed as the ratio of
AT1A-R, AT1B-R, or
AT2-R mRNA to GAPDH mRNA.
Details of the experimental procedures used to prepare the
membrane fraction and the binding assay were essentially the same as
those described previously by Takahashi et
al.39 In brief, whole adrenal tissue was
excised and homogenized in 20 volumes of ice-cold buffer
(0.25 mol/L sucrose containing 5 mmol/L Tris-HCl and 1 mmol/L
MgCl2, pH 7.5) in a Polytron PT-10 (Kinematica)
with 3 bouts of 10 seconds each at a setting of 7. The
homogenate was centrifuged at 500g for
15 minutes at 4°C. The supernatant was filtered through a double
layer of cheesecloth and centrifuged at 50 000g for
30 minutes at 4°C. The resulting pellet was washed twice with an
ice-cold incubation buffer (50 mmol/L Tris-HCl, 10 mmol/L
MgCl2, pH 7.5) by repeated resuspension and
recentrifugation. The final pellet was resuspended in
an ice-cold incubation buffer that contained 2 g/L BSA and 0.2 g/L
bacitracin. The membrane preparations were stored at -80°C until
use. Binding of
[125I]-Sar,1Ile8-Ang
II to membrane fractions was carried out as follows. The incubation
mixture contained 200 µL of membrane preparation (
150 to 300 µg
of protein), 50 µL of solution with
[125I]-Sar,1Ile8-Ang
II at various concentrations (specific activity, 2200 Ci/mmol), and 50
µL of incubation buffer (for total binding), unlabeled
Sar,1Ile8-Ang II (1
µmol/L; for nonspecific binding), PD123319 (10 µmol/L; for
AT1-R binding), or CV11974 (10 µmol/L; for
AT2-R binding). The incubation, started by the
addition of the membrane fraction, was carried out for 60 minutes at
25°C and terminated by addition of 2 mL of an ice-cold incubation
buffer. The mixtures were subjected to rapid filtration under reduced
pressure through glass-fiber Whatman GF/B filters (presoaked in the
incubation buffer containing 2 g/L BSA) using a Brandel 24R cell
harvester. The filters were immediately washed 4 times with 3 mL of
ice-cold incubation buffer. After the filters were dried, the
radioactivity trapped on the filters was quantified with an automatic
gamma counter (Aloka) at an efficiency of 83%. Specific binding of
[125I]-Sar,1Ile8-Ang
II was defined in terms of total radioactivity minus radioactivity due
to nonspecific binding. Each binding assay was carried out in
duplicate. The protein concentration was determined by the BCA protein
assay (Pierce Chemical Co) using BSA as a standard. To calculate the
maximal number of Ang II binding sites (Bmax) and
the binding constant (Kd), the values of
specific binding of Ang II to membrane were plotted according to the
method of Scatchard.39
Results are expressed as mean±SEM. Statistical analysis
was performed using 1-way ANOVA followed by Fisher's test for multiple
comparison. A value of P<0.05 was considered statistically
significant.
Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
Body Weight and Hemodynamic Variables
Body weights, SBPs, and heart rates before treatment were
comparable among the 3 groups (Table 1
). Body weight in the C
group increased, whereas it did not increase during the 1-week
treatment period in the L and L+B group.
View this table:
[in a new window]
Table 1. Body Weight and Hemodynamic
Variables
The expression levels of AT1A-R,
AT1B-R, and AT2-R mRNA in
the rat adrenal glands were determined by Northern blot
analysis (Figures 1 through 3). Densitometric analysis
indicated that the ratio of AT1A-R mRNA to GAPDH
mRNA was elevated in the L (1.68±0.15-fold, P<0.01) and
L+B (1.58±0.14-fold, P<0.01) groups compared with that in
the C group. Similarly, the ratio of AT1B-R mRNA
to GAPDH mRNA was elevated in the L (1.79±0.28-fold,
P<0.01) and L+B (1.63±0.20-fold, P<0.05)
groups compared with that in the C group. The ratio of
AT2-R mRNA to GAPDH mRNA did not differ among the
3 groups.
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Figure 1. Northern blot
analysis of AT1A-R mRNA in rat adrenal gland. Left,
Adrenal AT1A mRNA and GAPDH mRNA in control rats (C), rats
treated with L-NAME (L), and rats treated with L-NAME plus bunazosin
(L+B). A representative autoradiogram
is shown. Right, Densitometric data in which AT1A mRNA
levels were normalized by GAPDH mRNA level in 3 groups (n=6). mRNA
level of control rats was expressed as 1.0. **P<0.01 vs
C group. Values are expressed as mean±SEM. AT1A
mRNA was significantly increased in the L group (1.7-fold,
P<0.01 vs control) and L+B group (1.6-fold,
P<0.01 vs control).
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[in a new window]
Figure 2. Northern blot
analysis of AT1B-R mRNA in rat adrenal gland. Left,
Adrenal AT1B mRNA and GAPDH mRNA in control rats (C), rats
treated with L-NAME (L), and rats treated with L-NAME plus bunazosin
(L+B). A representative autoradiogram
is shown. Right, Densitometric data in which AT1B mRNA
levels were normalized by GAPDH mRNA level in 3 groups (n=6). mRNA
level of control rats was expressed as 1.0.
*P<0.05, **P<0.01 vs C group. Values
are expressed as mean±SEM. AT1B mRNA was
significantly increased in the L group (1.8-fold,
P<0.01 vs control) and L+B group (L+BUNA; 1.6-fold,
P<0.05 vs control).
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[in a new window]
Figure 3. Northern blot analysis of
AT2-R mRNA in rat adrenal gland. Left, Adrenal
AT2 mRNA and GAPDH mRNA in control rats (C), rats treated
with L-NAME (L), and rats treated with L-NAME plus bunazosin (L+B;
L+BUNA). A representative autoradiogram
is shown. Right, Densitometric data in which AT2 mRNA
levels were normalized by GAPDH mRNA level in 3 groups (n=6).
AT2 mRNA level was not changed among the 3 groups. mRNA
level of control rats was expressed as 1.0.
Figure 4 shows the saturation curves
and the scatchard plots of the binding of
[125I]-Sar,1Ile8-Ang
II to Ang II receptors in the membrane fraction of adrenal gland from
the 3 experimental groups. The calculated maximal binding sites
(Bmax) and dissociation constants
(Kd) are summarized in Table 2. The differences in
binding constant were not statistically significant among the 3 groups
(Table 2). Numbers of total receptor and AT1-R in
the L and L+B groups were significantly increased. The
AT2-R number was slightly increased in the L and
L+B groups; however, this difference was not statistically significant
(Table 2 and Figure 4). Therefore, the increased
AT1-R number accounted for the increased Ang II
receptor number in the L and L+B groups.
View larger version (21K):
[in a new window]
Figure 4. Saturation curves (left) and scatchard plot
analyses (right) of
[125I]-Sar,1Ile8-Ang II binding
to Ang II receptors in membrane from rat adrenal glands from the
control, L-NAME, and L-NAME plus bunazosin (L+B) groups (n=4). Membrane
protein (20 µg) was incubated with
[125I]-Sar,1Ile8-Ang II (0.5 to
20 nmol/L) in a final volume of 300 µL assay buffer containing 0.1%
BSA. Each point represents mean value of 4 rats in each group.
Kd value was not changed among the 3 groups,
whereas maximal binding of Ang II (Bmax) was significantly
increased in the L (P<0.01 vs control) and L+B
(P<0.05 vs control) groups. Data are shown in Table 3 
.
View this table:
[in a new window]
Table 2. Characterization of Ang II Receptors in
L-NAME–Treated
Rats shows the total,
AT1, and AT2 receptor
density in the adrenal gland of 3 groups measured using 5 nmol/L
[125I]-Sar,1Ile8-Ang
II. Consistent with the changes in total receptor density, the
AT1-R density in the L and L+B groups was
significantly (P<0.01) increased compared with that in the
C group.
View larger version (29K):
[in a new window]
Figure 5. Total Ang II, AT1, and
AT2 receptor density in rats from the control, L-NAME, and
L-NAME plus bunazosin (L+B) groups (n=4). Specific binding to
AT1 was measured in the presence of 10 µmol/L
PD123319, and specific binding to AT2 was measured in the
same way as AT1 in the presence of 10 µmol/L
CV11974. *P<0.05, **P<0.01 vs C group.
Values are expressed as mean±SEM. AT1 Bmax was
significantly increased in the L group (P<0.01 vs
control) and L+B group (P<0.01 vs control), but
AT2 Bmax was not changed among the 3
groups.
PAC was significantly increased in the L and L+B groups
compared with that in the C group, but PRA, serum ACE activities, and
serum potassium concentration were not different among the 3 groups
(Table 3). SCC was slightly
increased in the L and L+B groups, but there was no significant
statistical difference among the 3 groups (Table 3).
View this table:
[in a new window]
Table 3. Effects of Treatments on Biochemical
Variables
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
The present study demonstrates three major findings. First,
inhibition of NO synthesis by L-NAME in rats increased both
AT1A-R and AT1B-R mRNA
expression and the AT1-R number in the adrenal
gland, but it did not increase AT2-R mRNA
expression or AT2-R number. Second, inhibition of
NO synthesis increased PAC without significant increases of PRA, serum
ACE activity, SCC, or serum potassium concentration. Third,
normalization of blood pressure in L-NAME–treated rats did not affect
the expression levels of AT1A-R and
AT1B-R mRNA, the AT1-R
number of the adrenal gland, or PAC. This study is the first to show
that inhibition of NO synthesis upregulates the
AT1 receptors in vivo. -nitro-L-arginine (L-NNA)
compared with that in control animals; however, Simmons and Freeman
examined aldosterone secretion rate only 30 minutes after
L-NAME or L-NNA injection. We administered L-NAME for 1 week and
examined PAC. The difference between our results and those of Simmons
and Freeman may be derived from the difference in the period of L-NAME
treatment.
Acknowledgments
This study was supported in part by grants-in aid for scientific
research (06670725, 06404034, 07557346) from the Ministry of Education,
Science, and Culture, Tokyo; by research grants from the Uehara
Memorial Foundation, Tokyo, the Study Group of Molecular
Cardiology, Tokyo, and the Kaibara Morikazu Science
Promotion Foundation, Fukuoka; and a Kimura Memorial Heart Foundation
research grant for 1996, Kurume, Japan. The authors would like to thank
Fumiko Amano and Tomoko Takebe for their excellent
assistance.
References
Top
Abstract
Introduction
Methods
Results
Discussion
References
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J. Y.H. Chan, L.-L. Wang, C.-C. Ou, and S. H.H. Chan Downregulation of Angiotensin Subtype 1 Receptor in Rostral Ventrolateral Medulla During Endotoxemia Hypertension, July 1, 2003; 42(1): 103 - 109. [Abstract] [Full Text] [PDF]
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 S. P. Malhotra, V. M. Reddy, S. Thelitz, Y.-P. He, F. L. Hanley, S. Suleman, and R. K. Riemer Cavopulmonary anastomosis induces pulmonary expression of the angiotensin II receptor family J. Thorac. Cardiovasc. Surg., April 1, 2002; 123(4): 655 - 660. [Abstract] [Full Text] [PDF]
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 M. Chidambaram, J. A. Duncan, V. S. Lai, D. C. Cattran, J. S. Floras, J. W. Scholey, and J. A. Miller Variation in the Renin Angiotensin System throughout the Normal Menstrual Cycle J. Am. Soc. Nephrol., February 1, 2002; 13(2): 446 - 452. [Abstract] [Full Text] [PDF]
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E. SEELIGER, P. B. PERSSON, W. BOEMKE, G. MOLLENHAUER, B. NAFZ, and H. W. REINHARDT Low-Dose Nitric Oxide Inhibition Produces a Negative Sodium Balance in Conscious Dogs J. Am. Soc. Nephrol., June 1, 2001; 12(6): 1128 - 1136. [Abstract] [Full Text]
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R. Salemi, J. G. McDougall, K. J. Hardy, and E. M. Wintour Local inhibition of nitric oxide temporarily stimulates aldosterone secretion in conscious sheep in vivo Am J Physiol Endocrinol Metab, April 1, 2001; 280(4): E584 - E590. [Abstract] [Full Text] [PDF]
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L. Raij Workshop: Hypertension and Cardiovascular Risk Factors : Role of the Angiotensin II-Nitric Oxide Interaction Hypertension, February 1, 2001; 37(2): 767 - 773. [Abstract] [Full Text] [PDF]
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C. J. Hanke and W. B. Campbell Endothelial cell nitric oxide inhibits aldosterone synthesis in zona glomerulosa cells: modulation by oxygen Am J Physiol Endocrinol Metab, October 1, 2000; 279(4): E846 - E854. [Abstract] [Full Text] [PDF]
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M. d. Gasparo, P. Hess, B. Nuesslein-Hildesheim, P. Bruneval, and J.-P. Clozel Combination of non-hypotensive doses of valsartan and enalapril improves survival of spontaneously hypertensive rats with endothelial dysfunction Journal of Renin-Angiotensin-Aldosterone System, June 1, 2000; 1(2): 151 - 158. [Abstract] [PDF]
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C. J. Hanke, T. O'Brien, K. A. Pritchard Jr, and W. B. Campbell Inhibition of Adrenal Cell Aldosterone Synthesis by Endogenous Nitric Oxide Release Hypertension, January 1, 2000; 35(1): 324 - 328. [Abstract] [Full Text] [PDF]
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