bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Evidence That Loss of Intra-Renal Angiotensinogen Is not the Cause of Lethality in Angiotensinogen Deficient Mice
Authors: Ding Yueming , Sigmund Curt D
Published: March 2022

51

Angiotensinogen (Agt) deficient mice are born in normal numbers but die before weaning presumably due to renal dysfunction caused by severe vascular lesions. Since Agt is expressed in renal proximal tubule cells, we hypothesized that its loss is responsible for the lethal phenotype. We generated two models to test this hypothesis by breeding transgenic mice expressing human renin (R+) with mice expressing human Agt either systemically (A+) or kidney-specifically (KA+). We then bred double transgenic mice (R+/A+ or R+/KA+) with Agt-/- mice to generate R+/A+ Agt+/- or R+/KA+ Agt+/-. We then intercrossed the compound heterozygotes by brother/sister mating. Each offspring of this cross was genotyped for the presence of the human transgenes and at the Agt locus. The population was then stratified into groups (double transgenic and non-double transgenic), and the data was analyzed by χ
2
. Based on Mendelian genetics, if survival is not an issue, 25% of the offspring should be Agt-/-. Of 63 R-/A- (non-double transgenic) offspring, only 3 survivors were genotyped as Agt-/-, whereas of 68 R+/A+ offspring, 17 were Agt -/- and all survived to adults. These data demonstrate that systemic expression of Agt and Ang-II can rescue the Agt deletion. On the contrary, of 65 R-/KA- and 63 R+/KA+ offspring, not a single mouse was genotyped as Agt-/- (χ
2
= 0.0001). An analysis of 159 newborns indicated that Agt-/- mice were born in normal numbers (n= 41). Collection of dead 10-day old pups (n= 27) revealed an enrichment in Agt-/- (20 of 27 mice). Importantly, using RNase protection analysis we demonstrated that the KA+ transgene was temporally expressed during renal development similar to the endogenous Agt and at comparable levels. These data strongly support the notion that the loss of intra-renal Agt is not responsible for death in the Agt-/- mouse model. Taken together with our previous results, we conclude that the intra-renal renin-angiotensin system located in the proximal tubule plays an important role in blood pressure regulation, and may cause hypertension if overexpressed, but is not required for continued development of the kidney after birth.
Renal Vascular Kv and Ca
2+
Channel Alterations in the SHR are Dependent on Protein Kinase C Activity
Authors: Gelband Craig H
Published: March 2022

60

It is well established that in renal vascular smooth muscle cells of the SHR there is membrane depolarization, a decrease in Kv current and an increase in Ca
2+
current when compared to control WKY cells. It is also well accepted that protein kinase C (PKC) activity in SHR vascular smooth muscle is increased when compared to the WKY vasculature. The objective of this study was to investigate if the increased vascular PKC activity of the SHR plays a role in the regulation of SHR renal smooth muscle cell Kv and Ca
2+
channels. Basal PKC activity was increased ∼3-fold in the SHR renal arterioles when compared to the WKY (2.2±0.4 vs 6.3±0.6 nmol[
32
P]/min/mg protein, n=7, P≤0.01). Western blot analysis showed the presence of four different PKC isoforms, α, δ, ε and ζ, in both WKY and SHR renal resistance arterioles. Of the four isoforms, only the levels of PKC-α and ε were significantly increased in the SHR when compared to the WKY. To investigate the influence of PKC on vascular membrane potential, Kv and Ca
2+
current, renal resistance arteriolar cells were treated with PKC inhibitors (staurosporine or Calphostin C,1 μM) or activators (PMA or PDBu, 100 nM) for 1 hour and then subjected to whole cell patch clamp analysis. Interestingly, when SHR renal smooth muscle cells were treated with either PKC inhibitor, the membrane depolarization, decrease in Kv current and increase in Ca
2+
current usually observed were
abolished
, i.e. the SHR cells electrophysiologically resemble WKY cells. When WKY renal smooth muscle cells were treated with either phorbol ester, they caused membrane depolarization (22±3.5 mV, n=8), a decrease in Kv current (65±8.5%, n=10) and an increase in Ca
2+
current (125±11%, n=9), i.e. WKY cells electrophysiologically resemble SHR cells. These data suggest, that in renal arterioles of the SHR, increased PKC activity plays a role in the regulation of Kv and Ca
2+
channels, which in turn alters membrane potential, intracellular free Ca
2+
concentration and the resting tone of vascular smooth muscle in the kidney. This then would further decrease renal blood flow and exacerbate the hypertensive state.
Effect of Ac-SDKP on Cardiac and Renal Collagen Deposition in Aldosterone-Salt Hypertension
Authors: Peng Hong-Mei , Carretero Oscar A , Yang Fang , Yang Xiao-Ping , Rhaleb Nour-Eddine
Published: March 2022

62

Ac-SDKP is a natural substrate for the N-terminal active site of ACE. We have data showing that Ac-SDKP inhibits collagen synthesis both
in vitro
and
in vivo
. In the present study, we tested whether Ac-SDKP prevents cardiac and renal fibrosis in a renin-independent model of hypertension (aldosterone-salt) characterized by renal and cardiac fibrosis. Uninephrectomized adult SD rats were divided into 3 groups: control (saline) and aldosterone-salt (18 μg/d) alone or combined with Ac-SDKP 800 μg/kg/d.Saline,

aldosterone or Ac-SDKP was given s.c.
via
osmotic pump for 6 weeks. We found that Ac-SDKP decreased collagen content (hydroxyproline assay) in the LV, right ventricle (RV) and kidney, and LV collagen fraction, with no significant effect on BP and LV hypertrophy (Table). Our results suggest that Ac-SDKP prevents cardiac and renal fibrosis in renin-independent hypertension. This indicates that Ac-SDKP could participate in the antifibrotic effect of ACEi, since ACEi inhibit fibrosis in this model of hypertension and markedly increase plasma Ac-SDKP.
L-Arginine Prevents and Reverses the Hypertension Produced by Combining Chronic Hyperinsulinemia and Subpressor Inhibition of Nitric Oxide Synthase.
Authors: Bursztyn Michael , Mekler Judith , Bernheim Jacques
Published: March 2022

67

Previously we found that chronic hyperinsulinemia does not cause hypertension without sugar supplementation. An explanation may be insulin’s nitric oxide (NO) mediated vasodilation. To test this hypothesis we studied 4 groups of rats: INS (n=9) treated by a gradual increase of a subcutaneous insulin pellet; LNM (n=9) treated by L-NAME, 50mg/l in drinking water; INM (n=19) treated by the combination of insulin+L-NAME; and controls(CON)(n=9). Systolic blood pressure (SBP), was (mean±SD) by week 3, 122±17, 118±17, 118±24 mmHg in the CON, LNM, INS and 136±14 mmHg in the INM p≤0.03. By week 6, SBP was 128±14, 127±15, 118±13 mmHg in CON, LNM, INS and, 150±14 mmHg in the INM respectively p≤0.0005. Body weight was not affected. Excretion of urinary NO metabolites (NO
x
) (μmol/24h) was 21.6±2.5, and 24.3±2.9, in CON and INS, ,and 13.9±1.2, and 16.6±1.7 p≤0.05, in INS, and LNM respectively. Insulin levels were doubled 534±66, and 654±60pmol/l in INS and INM,
vs
270±18, and 264±50 pmol/l in CON, and LNM by week 6. There was no hypoglycemia and fructosamine levels were comparable. Urinary norepinephrine (nmol/24h) was lower in LNM 5.8±1.8
vs
CON 8.8±1.3, p≤0.05. In a subsequent experiment rats treated by both insulin+L-NAME as above received L-arginine 2g/l in drinking water, either from day 1 INMARG (n=12), or from day 30 INMAR30 (n=9), INM (n=4) and L-arginine ARG(n=4) served as controls. By week 4, SBP was 156±12, and 160±10 mmHg in INM and INMARG30 vs 126±26, and 132±18mmHg in ARG and INMARG p≤0.03. By week 8 SBP was 165±15 in INM, and 141±10, 116±24, 132±13 mmHg in INMARG, ARG, and INMARG30 respectively,p≤0.005. Urinary NO
x
(μmol/24h) were higher in ARG, and INMARG 23.7±3.7, and 19.2±3.8, p≤0.005
vs
14.5±6.5, and 13.2±5.2 in INM and INMARG30 respectively. Urinary norepinephrine was not affected. In both experiments food and water intake, urine volume, creatinine clearance and urinary Na
+
excretion were also not affected
.
In conclusion whereas hyperinsulinemia does not cause hypertension it does so when endothelial function is compromised. This effect reflects action of NOS as it is reversible and preventable with L-arginine.
Angiotensin II Type 1 Receptor Antagonism Prevented the Effects of Hypercholesterolemia on Plasma Fibrinolytic Balance in Rabbits.
Authors: Victoria Cachofeiro F , Oubina Pilar , HERAS Natalia de las , Vazquez-Perez Sandra , Navarro-Cid Josefa , Cediel Eva , Sanz-Rosa David , GASPARO Marc de , Ruilope Luis M , Lahera Vicente
Published: March 2022

P8

We have studied the effect of valsartan treatment (3 and 10 mg/kg/day) on plasma fibrinolytic balance in normo- and hypercholesterolemic rabbits. Animals were fed a normal chow or an experimental diet containing 1% cholesterol for 10 weeks. Systolic blood pressure, as well as plasma cholesterol, dimer D, plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (tPA) were measured. Plasma cholesterol concentrations were higher in rabbits fed the experimental diet compared with control ones. None of the doses of valsartan were able to affect either plasma cholesterol or blood pressure levels in any group.As compared with control animals hypercholesterolemic rabbits presented lower dimer D (0.37±0.07 mg/ml vs 0.96±0.13, p<0.05) and tPA levels (0.27±0.003 ng/ml vs 0.31±0.007, p<0.05) but higher PAI-1 levels (11.1±0.9 ng/ml vs 8.84±0.04, p<0.05). In cholesterol-fed rabbits, valsartan treatment (3 or 10 mg/kg/day) significantly increased both dimer D (0.73±0.1 mg/ml and, 1.3±0.2, respectively, p<0.05) and tPA (0.29±0.007 ng/ml and 0.3±0.01, respectively, p<0.05) levels. Likewise, both doses of valsartan reduced PAI-1 concentrations (9.4±0.1 ng/ml and 9.2±=.1, respectively, p<0.05). By contrast, valsartan treatment was unable to modify these parameters in control rabbits. All these data suggest that, in rabbits, hypercholesterolemia is associated with an impaired plasma fibrinolytic balance. In addition, prolonged treatment with valsartan prevented all these changes without modifying either plasma cholesterol or bllod pressure levels.This supports that angiotensin II may play a role in the thrombotic complications of athrosclerosis.
Human Endothelial Cells Bind and Activate Noncleavable Prorenin
Authors: Eijnden Mark Med van den , Sluiter Wim , Derkx Frans Hm , Reudelhuber Timothy L , Schalekamp Maarten Adh , Danser Alexander Hj
Published: March 2022

P15

Circulating prorenin (PR), following binding to endothelial mannose 6-phosphate (M6P) receptors, is activated proteolytically, and may thus play a role in vascular angiotensin (A) generation (Admiraal et al., J Hypertension 1999). In addition,
in vivo
studies with noncleavable PR (i.e., PR in which Lys in position 42 of the prosegment is mutated to Ala, thereby preventing cleavage by known proteases) in mice have revealed that PR may also generate AI following nonproteolytic activation (Methot et al., Circ Res 1999). Here, we studied the nature of the PR-activating enzyme in human umbilical vein endothelial cells (HUVECs), as well as the activation of noncleavable and nonglycosylated PR (i.e., PR mutated at its glycosylation sites) by these cells. HUVECs were incubated with 100 U/L recombinant human native, noncleavable, or nonglycosylated PR at 4°C or 37°C for 4 h with or without 10 mM M6P or inhibitors of serine (AEBSF, aprotinin), cysteine (E64, leupeptin), metallo (EDTA, phenanthrolin), or aspartic (pepstatin A) proteases. Intact and activated PR were measured in cell lysates by immunoradiometric assays with monoclonal antibodies (mAbs) directed against the prosegment (amino acids 20-43) or a renin-specific epitope. The prosegment-specific mAb recognizes intact PR only after nonproteolytic activation (either in the cells or after incubation of the lysates with the renin inhibitor remikiren for 48 h). At 37°C, HUVECs bound and internalized native and noncleavable, but not nonglycosylated, PR. Internalization did not occur at 4°C, and binding was blocked by M6P. More than 60% of the internalized native PR was activated. This was due to proteolytic cleavage, since the prosegment-specific mAb recognized <40% of PR after remikiren pretreatment, and did not detect PR without remikiren. Results with noncleavable PR were identical. None of the used protease inhibitors blocked the activation of native PR. In conclusion, HUVECs bind and activate PR through proteolytic cleavage of the prosegment. Binding is limited to glycosylated (i.e., M6P-containing) PR. Cleavage did not occur by any of the known proteases, and this may explain why noncleavable PR was also proteolytically activated in HUVECs.
Gender Difference in the Contribution of an Indomethacin-Sensitive Constrictor Factor to Phenylephrine Responsiveness in Rat Mesenteric Arteries
Authors: McKee Alyson P , Davison Cathy A
Published: March 2022

P22

The mechanism for gender differences in cardiovascular disease may be due, in part, to differences in vascular function. Based on previous studies from our laboratory, we hypothesized that there is enhanced production of a vasoconstrictor cyclooxygenase product in arteries from males when compared to those from females. We studied three month-old male and female Sprague-Dawley rats (n=6 in each group). Small mesenteric arteries (∼400 μm) were isolated, pressurized, and the outer diameter was measured. Arteries from each rat were paired: one had intact endothelium (ENDO +) and the other was mechanically denuded (ENDO -). Dose-response curves to the α
1
-adrenergic agonist, phenylephrine (PE), were performed in the absence and presence of the cyclooxygenase inhibitor, indomethacin (INDO; 10 μM). Negative log EC
50
values were calculated as an index of PE sensitivity and compared between groups using ANOVA and lsd. There were no differences in the sensitivity to PE in ENDO + arteries from males (6.07±0.07) and females (6.12±0.10, p=0.93). In ENDO + arteries from females, the PE sensitivity was unchanged in the presence of INDO (6.11±0.13, p=0.94 when compared to control). However, INDO significantly decreased PE sensitivity in ENDO + arteries from males (5.70±0.08, p=0.01 when compared to control). Endothelium denudation had no significant effect on PE sensitivity in males or females. In denuded arteries from females, INDO produced no change in PE sensitivity (denuded female: 6.08±0.09, denuded + INDO: 5.88±0.13, p=0.23). In contrast, INDO produced a significant decrease in sensitivity in denuded arteries from males (denuded male: 6.33±0.14, denuded + INDO (5.94±0.09, p=0.03). The magnitude of the shift in PE sensitivity produced by INDO (Δ EC
50
)in males was equivalent in ENDO + (0.37±0.07) and ENDO - (0.39±0.09, p=0.9, Student’s t-test) arteries. In conclusion, arteries from male rats produce more of an indomethacin-sensitive vasoconstrictor factor than arteries from female rats. The site of enhanced production of this cyclooxygenase product in males is not the endothelium, but may be vascular smooth muscle.
Superoxide Excess in Hypertension and Aging: A Common Cause of Endothelial Dysfunction?
Authors: Hamilton Carlene A , McIntyre Martin , Brosnan Mary J , Graham Delyth , Dominiczak Anna F
Published: March 2022

P23

Objective: Excess superoxide (O
2
-
) contributes to the endothelial dysfunction in 4 month (mo) old stroke prone spontaneously hypertensive rats (SHRSP). We sought to determine the relationship between endothelial function and age in normotensive Wistar-Kyoto (WKY) and SHRSP. Methods: Aortic rings were removed from female WKY and SHRSP at 4mo and 12mo of age. Nitric oxide (NO) bioavailability was measured by the size of contraction produced in response to the nitric oxide synthase (NOS) inhibitor L-NAME (0.1mmol/L). O
2
-
generation by aortic rings was measured by lucigenin chemiluminescence before and after removal of the endothelium, or incubation with L-NAME (0.1mmol/L), or the NAD(P)H oxidase inhibitor diphenyleneiodinium (DPI, 0.1mmol/L). Results: Contraction to L-NAME (% of PE ± SEM) was significantly lower in 12mo WKY (296 ± 30, n=11) compared to 4mo WKY (523 ± 51, n=15; P=0.0009) and in also in 12mo SHRSP (220 ± 28, n=8) compared to 4mo SHRSP (341 ± 26, n=16; P=0.005). O
2
-
generation (nmol/min/mg ± SEM) was significantly greater in 12mo WKY (2.83 ± 0.30, n=21) compared to 4mo WKY (1.06 ± 0.20, n=7; P=0.0001), but the difference between 12mo SHRSP (3.44 ± 0.31, n=13) and 4mo SHRSP (2.98 ± 0.49, n=9) did not achieve significance. Removal of the endothelium resulted in a significant reduction in O
2
-
generation in 12mo SHRSP (2.49 ± 0.18
v
3.35 ± 0.29, n=12; P=0.009). In 12mo WKY the reduction was not statistically significant. L-NAME significantly reduced O
2
-
generation in 12mo SHRSP (2.04 ± 0.54
v
1.5 ± 0.41, n=5; P=0.03), but made no difference to 12mo WKY. DPI significantly reduced O
2
-
generation in 12mo WKY (2.83 ± 0.28
v
1.42 ± 0.27, n=4; P=0.009) and also 12mo SHRSP (2.25 ± 0.0.43
v
0.64 ± 0.07, n=7; P=0.01). Similar increases in O
2
-
generation were observed with age and hypertension in carotid arteries (WKY: 4mo 0.88 ± 0.18, 12mo 3.88 ± 0.50; SHRSP: 4mo 3.35 ± 0.46, 12mo 4.89 ± 0.55). Conclusion: NO bioavailability decreases with age in WKY and SHRSP females. O
2
-
generation increases with age in WKY and may contribute to the reduced NO by scavenging. Both NOS and NAD(P)H oxidases appear to be important contributors to the age related increase in O
2
-
.
Tempol, Vitamin C and Vitamin E Improve Endothelial Dysfunction, Regress Vascular Hypertrophy and Prevent Progression of Hypertension and Renal Dysfunction in Stroke-Prone Shr
Authors: Park Jeong Bae , Touyz Rhian M , Chen Xin , Schiffrin Ernesto L
Published: March 2022

P35

Antioxidant vitamins reduce oxidative stress in vascular injury associated with atherosclerosis and balloon injury. The role of these agents in the pathogenesis of hypertension is unclear. We investigated effects of vitamins C and E and the superoxide dismutase (SOD) mimetic, tempol, on development of blood pressure, vascular structure and endothelial function in salt-loaded stroke-prone SHR (SHRSP). 16 week-old SHRSP (n=26) on a high salt diet (4% NaCl) were randomly divided into 4 groups: control (C), Vit C (1000 mg/d), Vit E (1000 IU/d) and tempol (1 mmol/d). Systolic blood pressure (SBP) and renal function were assessed weekly. 6 weeks after treatment rats were killed. Vascular structure (media:lumen ratio) and endothelial function (acetylcholine (Ach)-induced vasodilation) were assessed in small mesenteric arteries mounted as pressurized preparations. SBP increased from 204± to 265±6 mmHg in C group. Progression of hypertension was prevented in Vit C (234±4 mmHg), Vit E (227±11mmHg) and tempol (208±8 mmHg) groups. Development and severity of proteinuria was delayed in all treated groups compared with C. The media:lumen ratio was reduced (p<0.001) in the Vit E (7.4±0.5%) and tempol (7.2±0.01%) groups compared with C group (12±0.1%). Structure was not significantly altered in the Vit C group. Maximal Ach-induced dilation was significantly improved in all treated groups, particularly in the Vit C group (85±4 % vs C 40±9 %, p<0.01). In conclusion antioxidant vitamins and tempol prevent progression of hypertension and improve renal dysfunction in SHRSP. These processes are associated with improved endothelial function and regression of vascular hypertrophy in small arteries. Our data suggest that oxidative stress plays a role in vascular and renal damage associated with severe hypertension in salt-loaded SHRSP.
Role of Gap-Junctions in Endothelium-Dependent Hyperpolarization in Rat Small and Large Mesenteric Arteries
Authors: Goto Kenichi , Fujii Koji , Abe Isao
Published: March 2022

P39

In arteries, acetylcholine (ACh) releases endothelium-derived hyperpolarizing factor (EDHF) which is distinct from nitric oxide. The identity of EDHF is still elusive; however several recent studies suggests the possible involvement of myoendothelial gap-junctions in small arteries. To elucidate the involvement of gap-junctions in EDHF responses, we examined the effects of 18α-glycyrrhetinic acid (18α-GA, 10
-4
mol/L), a gap junction inhibitor, on endothelium-dependent hyperpolarization and relaxation to ACh in rat small and large mesenteric arteries. Experiments were perfomed in the presence of indomethacin (10
-5
mol/L) and NG-nitro-L-arginine (10
-4
mol/L) . In large arteries, ACh (10
-6
mol/L)-induced hyperpolarization measured from intimal side, was attenuated by the 18α-GA (12.4±1.2 vs. 8.4±0.8mV in the absence and presence of 18α-GA, p<0.05, n=7). In rings pre-contracted with norepinephrine (5×10
-7
mol/L), ACh-induced relaxation was also attenuated (maximal relaxation, 71.5±6.3 vs. 50.5±6.4%, p<0.05, n=8 ). In small arteries, ACh-induced hyperpolarization, measured from either adventitial side or intimal side was attenuated by 18α-GA (adventitial side, 12.3±1.2 vs. 4.6±0.7mV, p<0.05, n=8; intimal side, 8.0±0.7 vs. 5.0±0.7mV, p<0.05, n=4). On the other hand, smooth muscle hyperpolarization to levcromakalim, a direct activator of ATP-sensitive K
+
-channels, did not differ in the absence and presence of 18α-GA (16.7±0.6 vs. 16.3±1.5mV, ns, n=8 and n=6 respectively). These findings suggest that myoendothelial gap-junctions partly contribute to the EDHF-mediated responses both in rat small and large mesenteric arteries.
Vascular Reactivity to Calcitonin Gene Related-Peptide Is Enhanced in Subtotal Nephrectomy-Salt Hypertension.
Authors: Scott C Supowit M , Stephanie W Watts F , Huawei Zhao M , Donna H Wang F , Donald J DiPette M
Published: March 2022

P44

We previously demonstrated that CGRP plays a counterregulatory role to attenuate the BP increase in subtotal nephrectomy-(SN)-salt-induced hypertension. This effect was observed in the absence of any increase in neuronal CGRP expression in this hypertensive model, suggesting that the mechanism of this compensatory vasodilator response is enhanced vascular reactivity to CGRP. To test this hypothesis, hypertension was induced in Sprague-Dawley rats (150-175 g, n=5) by SN and 1% saline drinking water. Controls (n=5) were sham operated and given tap water to drink. After eleven days, systolic BP was significantly higher in the SN compared to the control rats (220±7 vs 140±4 mmHg). Vascular reactivity was then examined in isolated endothelium-intact superior mesenteric arterial strips. Phenylephrine (10
-9
-3×5
-5
M)-induced contraction was not different between the two groups. CGRP (10
-11
-5×10
-8
M)-induced maximum relaxation in phenylephrine-contracted arteries was not altered between the SN and control arteries, however, CGRP was significantly more potent in the arteries from the SN group (EC50, 0.7±0.2 vs 2.5±0.8 nM). Phenylephrine-contracted arteries were also treated with forskolin (10
-9
-10
-6
M) since increased intracellular cAMP levels is a prominant mechanism linked to CGRP-mediated vasodilation. While no change in efficacy was observed, there was a marked decrease in response to forskolin in SN arteries (EC50, 327±146 vs 20±8 nM). To examine the BP response to exogenous CGRP in vivo, identical groups of SN and control rats (n=6/group) had i.v. (for CGRP administration) and arterial (for continous BP monitoring) catheters surgically placed and were studied in a concious, unrestrained state. Baseline mean BP was higher in the SN rats compared to the controls (173±5 vs 125±4 mmHg). Administration of CGRP (0.25μg/kg i.v.) resulted in a significantly greater decrease in mean BP in the SN rats compared to controls (-19±4 vs -9±1 mmHg). These data suggest that the counterregulatory effects of CGRP observed in SN-hypertension result, at least in part, from a cAMP-independent enhancement in vascular reactivity to this potent vasodilator.
Impaired β-Adrenoceptor-Mediated Hyperpolarization in Resistance Arteries from Prehypertensive Shr
Authors: Goto Kenichi , Fujii Koji , Abe Isao
Published: March 2022

P49

Stimulation of vascularβ-adrenoceptors leads to smooth muscle hyperpolarization, presumably through theβ-adrenoceptors/Gs protein/adenylate cyclase/ATP-sensitive K
+
-channels (KATP) signaling cascade, which has been shown to play an important role in the sympathetic control of membrane potential. Impairedβ-adrenoceptor-mediated hyperpolarization has been reported in established stage of hypertension in rat models. However, it is not known whether such an abnormality exists in prehypertensive stage. To clarify this point, we comparedβ-adrenoceptor-mediated hyperpolarization using microelectrodes in mesenteric resistance arteries from 5-week-old, prehypertensive spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto rats (WKY). Systolic blood pressure did not differ between these rats (137.5±4.3 vs. 138.1±2.3mmHg; P=ns, n=10). Isoproterenol-induced hyperpolarization was significantly less in prehypertensive SHR than in WKY (10
-7
mol/L; -4.6±0.6 vs. -7.8±0.8mV; P<0.01, 10
-6
mol/L; -7.8±0.5 vs. -9.8±0.6mV; P<0.05; n=9 in each). Furthermore, hyperpolarization to cholera toxin, a direct activator of Gs protein, was also impaired in SHR (10
-6
mol/L; -2.1±0.9 vs. -4.5±0.6mV; P<0.05; n=6 in each). On the other hand, hyperpolarization to forskolin, a direct activator of adenylate cyclase, and that to levcromakalim, a KATP opener, were comparable in both groups. These findings suggest thatβ-adrenoceptor-mediated hyperpolarization is defective already in prehypertensive SHR, presumably due to an abnormality at the level of Gs protein. In view of the importance of membrane potential in the control of vascular tone, such a defect may play a pathogenic role in genetic hypertension through an increase in vascular resistance.
Myocardial Infarction Increases Cardiac Interstitial Fluid Vasopressor and Inflammatory Factors in Conscious Rats.
Authors: Siragy Helmy M , Lindner Jonathan , Gasparo Marc de , Kaul Sanjiv , Carey Robert M
Published: March 2022

P59

Increased activity of the renin-angiotensin system has been observed in congestive heart failure, left ventricular hypertrophy and post-myocardial infarction. However, the exact role of angiotensin II (Ang II) in development of these pathologic conditions is not well elucidated. Using an indwelling intramyocardial microdialysis catheter in conscious rats, we measured changes in cardiac interstitial Ang II, thromboxane B2 (TXB2) endothelin-1 (ET-1) and prostaglandin E2 (PGE2) in control animals (n=10) and 24h after complete occlusion of left anterior descending artery (LAD, n=10) in conscious rats. Cardiac interstitial Ang II was 307±27 pg/ml vs. 842±40 pg/ml (P<0.01), TXB2 154±6 vs. 193±31 pg/ml (P<0.01), ET-1 24±1 vs. 58±1 pg/ml (P<0.01) and PGE2 397±52 vs. 707±50 pg/ml (P<0.01) in control vs. LAD occlusion, respectively. We conclude that early after infarction, cardiac interstitial Ang II, TXB2, ET and PGE2 increase and may serve to promote local inflammation, vasoconstriction, thrombosis and remodeling.
A2B Adenosine Receptors Mediate the Anti-Mitogenic Effects of Adenosine in Cardiac Fibroblasts
Authors: Dubey Raghvendra K , Gillespie Delbert G , Jackson Edwin K
Published: March 2022

P85

Adenosine inhibits growth of CFs; however, the adenosine receptor subtype that mediates this anti-mitogenic effect remains undefined. Using specific ADE receptor antagonists and agonists and antisense oligonucleotides (OLIGO) against A2B receptors, we investigated the role of A2B receptors in inhibiting cardiac fibroblast growth. PDGF (25ng/ml)-induced DNA synthesis, cell number and collagen synthesis in CFs were inhibited by A2 (chloroadenosine [Cl-Ad]and MECA), but not by A1 (CPA), A2a (
CGS21680
) or A3 (AB-MECA),receptor agonists.The inhibitory effects of 1μM MECA and Cl-Ad were reversed by A1/A2 (DPSPX; 10nM), but not by A1 (DPCPX; 10nM), receptor antagonists. In CFs treated with antisense, but not sense or scrambled, OLIGOs to the A2B receptor, both basal and PDGF-induced DNA synthesis was enhanced by 70±4% and 64±5% respectively. Moreover, the inhibitory effects of Cl-Ad and MECA were completely abolished in CFs treated with antisense, but not sense and scrambled, OLIGOs. In conclusion, A2B receptors mediate the anti-mitogenic effects of adenosine suggesting that A2B receptors are importantly involved in the regulation of CF biology. Thus, A2B receptors may play a critical role in regulating cardiac remodeling associated with CF proliferation.
Production and Actions of Superoxide in the Renal Medulla
Authors: Zou Ai-Ping , Li Ninjun , Cowley Allen W
Published: March 2022

P101

There is increasing evidence that oxidant stress is involved in the development of hypertension. Given the importance of renal medullary blood flow (MBF) in the long-term control of arterial blood pressure (AP), we hypothesized that renal medullary redox status may importantly contribute to the control of AP through alteration of MBF. The present study first characterized the biochemical pathways for superoxide (O
2
-.
) production in the rat kidney. Using the dihydroethidium/DNA fluorescence spectrometry, the production of O
2
-.
was monitored with the tissue homogenates from different kidney regions incubated in microtiter plates with either NADH or NAHPH, or xanthine, or succinic acid/antimycin A, which are the substrates of NADH/NADPH oxidase, xanthine oxidase and mitochondrial respiratory chain, respectively. The production of O
2
-.
via NADH oxidase was greater (p<0.05) in the renal cortex and outer medulla (OM) than papilla. The mitochondrial enzyme activity for O
2
-.
production was higher (p<0.05) in the OM than cortex and papilla. Overall, the renal OM exhibited greater enzyme activities for O
2
-.
production. In anesthetized rats, renal medullary interstitial infusion of a membrane-permeable SOD mimetic, 4-hydroxy-tetramethyl piperidine-1-oxyl (TEMPOL, 30 μmol/kg/min) significantly increased MBF by 31%, as measured by laser-Doppler flowmetry and increased sodium excretion by 39%. Renal cortical blood flow and AP were unchanged. We conclude that (i) renal medullary O
2
-.
may be primarily produced in the renal OM; (ii) both NADH oxidase and intramitochondrial enzymes are responsible for the O
2
-.
production in this kidney region; (iii) O
2
-.
exerts a tonic regulatory action on vascular tone in the renal medullary circulation.
Regulation of Angiotensin II Receptors in Medullary Thick Ascending Limbs
Authors: Wang Donna H , Li Jianping
Published: March 2022

P102

Angiotensin II (Ang II) is an important regulator of the function of the medullary thick ascending limb of loop of Henle (MTAL). Recent studies showed that changes in Ang II receptor expression occur and underlie changes in the function of proximal tubules during altered sodium intake. The present experiment was designed to determine 1) whether expression of the type 1 Ang II (AT1) receptor in MTAL is regulated by altered sodium intake, and 2) the specific pathway(s) mediating sodium-induced AT1 expression in MTAL. Wistar rats were fed a normal sodium (0.5%, NS), low sodium (0.07%, LS), or high sodium (4%, HS) diet for 2 weeks. Northern blot analysis and radioligand binding showed that in rats fed a normal sodium diet the rank of order for both AT1 mRNA expression and receptor density was outer medulla>cortex>inner medulla. Sodium restriction significantly increased both AT1 mRNA expression and receptor density in the outer medulla. In contrast, neither AT1 mRNA expression nor receptor density in the outer medulla was altered by sodium loading. Losartan treatment (3 mg/kg/per day by oral gavage for 2 weeks) prevented low sodium-induced upregulation of the AT1 receptor in the outer medulla, but it had no effect on AT1 expression in the outer medulla of rats fed a normal sodium diet. Highly purified suspensions of MTAL were isolated from rats fed a normal or low sodium diet. Low sodium intake significantly increased AT1 mRNA level by 184% and AT1 receptor density by 58% in MTAL. Primary culture of MTAL cells were treated with PBS, Ang II (10
-8
M), and Ang II + 17 octadecynoic (17 ODYA, 10μM). Ang II caused about 2-fold increase in AT1 mRNA levels, and this increase was dinimished by about 30% by the addition of 17 ODYA. We conclude that 1) sodium restriction but not sodium loading increases AT1 receptor expression in MTAL, 2) low sodium-induced upregulation of the AT1 receptor in MTAL is Ang II-dependent, and 3) Ang II induced upregulation of the AT1 receptor in MTAL is mediated, at least in part, by cytochrome P450 pathways.
Angiotensin-I Converting Enzyme Inhibitor Improves Decreased Endothelial Function in Elderly Hypertensive Patients with Arteriosclerosis Obliterans
Authors: Okuma Hiroshi , Morimoto Shigeto , Sakurai Shoroku , Onishi Miyuki , Onishi Toshio , Ogihara Toshio
Published: March 2022

P123

Endothelial function in elderly hypertensive patients with arteriosclerosis obliterans (ASO) has not been evaluated. In this study, we examined whether endothelial function is impaired, and whether antihypertensive agents affect the vasodilatory responses, in elderly hypertensive patients (83 + 8 years) without (n=46) and with (n=24) ASO (ankle-brachial pressure index <0.2). Patients were treated with monotherapy of either temocapril (2 mg, 14 ASO patients and 26 non-ASO patients) or amlodipine (2.5 mg, 10 ASO patients and 20 non-ASO patients) for 6 months. Endothelia function was determined by flow-mediated endothelium-dependent vasodilation during reactive hyperemia after 5 minutes of cuff occlusion (MAX-RH) in the legs and forearms. Not only the MAX-RH in 35 ASO legs (4.7 ± 1.8 ml/min/100ml)Å@but also the value in 13 non-ASO legs (21.0 ±5.0) in the ASO patients were significantly (p<.001 and p=.037) decreased compared to the value in 92 legs in age- and sex-matched control hypertensive subjects (24.1 ±45). Moreover, the MAX-RH in the right forearm in the 24 ASO patients (23.3 ±4.4) was significantly (p=.003) decreased compared to that in the 46 control subjects (26.5 + 3.9). Blood pressure was similarly decreased by the treatment with temocapril or amlodipine. Response to nitroglycerin (0.3 mg) was not changed by either drug. Treatment with temocapril significantly improved the MAX-RH of not only legs (27.3 ±4.5) and forearm (28.1±3.6) in control hypertensive subjects, but also ASO legs (5.7 ±1.5), non-deseased legs (25.3±2.6), and forearm (25.8±3.8) in the ASO patients. However, treatment with amlodipine did not affect the MAX-RH. These results indicate that generalized endothelial function is decreased in elderly hypertensive patients with ASO, and treatment with the angiotensin-converting enzyme inhibitor temocapril improves the decreased vasodilatory response to reactive hyperemia, suggesting its beneficial effect on endothelial function in elderly hypertesive patients with ASO.
Elevated Na
+
/Li
+
Countertransport and Cytosolic Ca
2+
Represent Separate and Distinct Phenotypes in Essential Hypertension
Authors: Romero Jose R , Rivera Alicia , Monari Alessandra , Ceolotto Giulio , Semplicini Andrea , Conlin Paul R
Published: March 2022

P124

Attempts to understand the pathogenesis of essential hypertension have focused on identifying intermediate phenotypes such as defects in cation metabolism. Elevated red blood cell sodium-lithium countertransport (SLC) activity is frequently present in hypertensive patients. Cytosolic calcium (Ca
cyt
) is also elevated in blood cells from hypertensive patients. However, despite their frequent occurrence in hypertensive patients, these two markers of cation homeostasis have not been simultaneously investigated in the same individuals. We studied lymphocyte Ca
cyt
and red cell SLC activity in hypertensive (n = 43) and normal subjects (n = 22) to determine whether elevated SLC activity and lymphocyte Ca
cyt
occur in the same individuals. Red cell SLC and lymphocyte Ca
cyt
were significantly (
P
<0.01) higher in the hypertensive patients
vs.
normotensives. However, SLC activity and Ca
cyt
were significantly but
inversely
correlated (r=-0.42,
P
<0.01). Patients with low Ca
cyt
(84 ± 5 nM) had elevated SLC (0.41 ± 0.03 mmol/L cell x h, P< 0.05) whereas those with elevated Ca
cyt
(188 ± 15) had lower SLC (0.32 ± 0.03 mmol/L cell x h, P< 0.05). We then compared both phenotypes to a separate intermediate phenotype, fasting insulin. SLC and fasting insulin levels were significantly and positively correlated (r=0.45,
P
<0.01), consistent with prior studies showing elevated SLC activity in the setting of hyperinsulinemia. Ca
cyt
was
inversely
correlated with fasting insulin (r=-0.55,
P
<0.001). Individuals with insulin levels above the median (15 mU/ml) had significantly (
P
<0.01) higher SLC activity (0.43 ± 0.03
vs
. 0.28 ± 0.02 mmol/L cell x h) and significantly (
P
=0.017) lower Ca
cyt
(177 ± 18
vs.
105 ± 8 nM). Thus, elevated SLC activity and elevated lymphocyte Ca
cyt
are separate and distinct ion transport phenotypes in hypertensive patients, but they are linked through a relationship to hyperinsulinemia that is direct with SLC and inverse with lymphocyte Ca
cyt
.
Exaggerated Stress Responses of a Chromosome-1 Congenic Strain Derived from Shrsp/Izm and Wky/Izm
Authors: Nabika Toru , Ikeda Katsumi , Kawakami Kohei , Gonda Tatsuo , Nara Yasuo , Masuda Junichi , Yamori Yukio
Published: March 2022

P136

Background: QTL mapping studies showed that the rat chromosome 1 includes a gene responsible for hypertension in SHR. To understand roles of this putative hypertension gene on the cardiovascular physiology, we studied stress responses of a congenic strain with the chromosome-1 blood pressure (BP) QTL transferred from SHRSP/Izm. Methods: The region between D1Wox29 and D1Rat112 (∼60cM) was introgressed from SHRSP/Izm to WKY/Izm by repeated backcrossing. The established congenic strain (CONG) covered a 100:1 support interval for the BP QTL found in the previous study (Am J Hypert 1999;12:1098). After telemetry probes were implanted, age-matched male CONG and WKY (5-6 month old) were used in the following experiments; 1) Restraint stress: rats were put in small tubes for 1h at room temperature and BP was monitored with radiotelemetry. 2) Cold stress: rats were kept at 4 C for 2h and BP was monitored using telemetry. Results: Without the stresses, BP measured with telemetry was not different between WKY and CONG (Table) although tail-cuff measurement gave a significant difference in BP between the two strains (141±3.5 and 154±8.3mmHg for WKY and CONG, p<0.0001). During the exposure to the restraint stress, CONG showed greater BP increase than did WKY (Table). Similar exaggerated responses in CONG were observed during the cold stress as well. Conclusion: The hypertension gene in the chromosome-1 QTL region may modulate cardiovascular responses to the stresses probably through the sympathetic nervous system.
Endothelin-1 Enhances Eicosanoids-Induced Coronary Smooth Muscle Contractility and [Ca
2+
]
I
by Activating a Protein Kinase C-Sensitive Ca
2+
Entry Pathway
Authors: Sirous Zohreh N , Fleming John B , Khalil Raouf A
Published: March 2022

P151

Endothelin-1 (ET-1) has been implicated in the pathogenesis of coronary vasospasm by enhancing the coronary vasoconstrictor response to vasoactive eicosanoids; however, the cellular mechanisms involved are unclear. We investigated whether physiological concentrations of ET-1 enhance prostaglandin F
2α
(PGF
2α
)-induced coronary smooth muscle contraction by increasing [Ca
2+
]
i
and the Ca
2+
mobilization mechanisms of coronary vasoconstriction. Single smooth muscle cells were freshly isolated from the left anterior descending coronary artery of castrated male pigs and labeled with the Ca
2+
indicator fura-2 or with antibodies to specific protein kinase C (PKC) isoforms. In Hank’s solution (1 mM Ca
2+
), ET-1 (30 pM) caused a small increase in cell contraction (9%) and [Ca
2+
]
i
(106±5 nM). PGF
2α
(10
-7
M) increased cell contraction to 11% and [Ca
2+
]
i
to 121±7 nM. In cells pretreated with ET-1 (30 pM) for 30 min, PGF
2α
(10
-7
M) significantly increased cell contraction to 32% and [Ca
2+
]
i
to 217±8 nM. Membrane depolarization by 24 mM KCl, which stimulates Ca
2+
entry from the extracellular space, caused 12% cell contraction and increased [Ca
2+
]
i
to 152±6 nM. In cells pretreated with ET-1, KCl significantly increased cell contraction to 34% and [Ca
2+
]
i
to 306±8 nM. In Ca
2+
-free Hank’s, caffeine (10 mM), which stimulates Ca
2+
release from intracellular stores, caused cell contraction (9%) and a transient increase in [Ca
2+
]
i
(417±14 nM). ET-1 did not significantly affect the caffeine contraction or [Ca
2+
]
i
. ET-1 caused significant translocation of α-PKC from the cytosol to the cell membrane, suggesting activation of the isoform. The PKC inhibitor Gö6976 (10
-6
M) completely inhibited the ET-1 induced α-PKC translocation and the enhancement of PGF
2α
− and KCl-induced cell contraction and [Ca
2+
]
i
. Thus, ET-1 enhances PGF
2α
-induced coronary smooth muscle contractility and [Ca
2+
]
i
by enhancing Ca
2+
entry from the extracellular space, but not Ca
2+
release from intracellular stores. The results suggest that the enhancement of PGF
2α
-induced Ca
2+
entry by ET-1 involves activation and translocation of α-PKC isoform.
Gangliosides GM1 and GM2 Stimulate Vascular Smooth Muscle Cell Growth and the Mitogen-Activated Protein Kinase Signaling Transduction Pathway
Authors: Sachinidis Agapios , Seul Claudia , Seewald Stefan , Gouni-Berthold Ioanna , Ko Yon , Vetter Hans
Published: March 2022

P156

The gangliosides GM1, GM2 and GM3 appear to be involved in the development of cardiovascular diseases. However, little is known about the direct effects of gangliosides on vascular smooth muscle cell growth (VSMC) growth and mitogenic signal transduction pathway. Stimulation of quiescent VSMCs with GM1 (5, 20, 50 and 100 μM) resulted in a dose-dependent increase in [
3
H]thymidine incorporation from 41±3.5 (basal value) to 64±3.7, 69.6±7.1, 180±11 and 190±10.7 (mean±SE, n=3), respectively. GM3 (1 to 50 μM) had no effects on DNA synthesis whereas 100 μM GM3 caused a reduction in DNA synthesis from 41±3.5 to 12 ±1.4 cpm/μg protein (mean±SE, n=3). Stimulation of quiescent VSMCs with 50 μM GM1 and GM2 caused a 95±7% and 100±4% increase in cell counts (mean±SE, n=3) whereas 50 μM GM3 had no effects. Phosphorylated (activated) MAP kinases were detected by the enhanced chemiluminescence western blotting method using a phospho-specific extracellular signal-response kinases (ERK)1/2 antibody, a phospho-specific p38 MAPK antibody and a phospho-specific c-Jun N-terminal kinase/stress-activated protein kinases (JNK/SAPK) (the p54 and p46 isoforms) antibody. Stimulation of the cells with 50 μM GM1 and GM2 for 1 to 30 min resulted in time-dependent increase of phosphorylated ERK1/2 and p54/p46 with a maximum at 15 min (5-fold increase). The effect of GM1 and GM2 on the ERK1/2 and JNK/SAPK was also dose-dependent with maximal effect at 50 μM. Gangliosides had no effect on p38 MAPK phosphorylation. Treatment of the cells with 100 ng/ml pertussis toxin (PTX) (G
i
protein inhibitor) and 20 μM PD 98059 (MEK inhibitor) caused a complete inhibition of the phosphorylation of the ERK1/2 and JNK/SAPK. We conclude that the gangliosides may be involved in the development of cardiovascular diseases via proliferation of VSMCs. Furthermore, like bioactive lipids, gangliosides are able to stimulate the MAP kinase pathway via a PTX-sensitive G
i
coupled receptor.
Adrenomedullin Stimulates Cell Proliferation and DNA Synthesis in Rat Adrenal Zona Glomerulosa (ZG) Via Activation of Tk-Mapk Signalling Pathways
Authors: Ceolotto Giulio , Baritono Elisabetta , Andreis Giacomina Paola , Nussdofer Gastone , Semplicini Andrea
Published: March 2022

P161

Aim: To investigate the
in vivo
effect of adrenomedullin (ADM) on the proliferative activity of the rat adrenal cortex, using an intact left gland
in situ
perfusion model. Adrenal glands were exposed to ADM and other chemicals, added to the perfusion medium, for 180 min. Results: ADM concentration-dependently increased the mitotic index and [
3
H]thymidine incorporation into DNA in the ZG (maximally effective [ADM] being 10
-8
M), but not in inner adrenocortical layers. Both the calcitonin gene-related peptide (CGRP) type 1receptor antagonist CGRP(8-37) and the ADM C terminal fragment ADM(22-52) equipotently counteracted the effect of 10
-8
M ADM. The adenylate cyclase (AC) inhibitor SQ-22536 (10
-4
M), and the protein kinase (PK)A inhibitor H-89 (10
-5
M) did not affect ADM-elicited increase in DNA synthesis, although counteracting the ZG proliferogenic action of 10
-9
M ACTH. The phospholipase (PL) C inhibitor U-73122 (10
-5
M), and the PKC inhibitor calphostin-C (10
-5
M), which significantly inhibited the ZG proliferogenic effect of 10
-9
M angiotensin-II (Ang II) were also uneffective on ADM response. Both ADM and Ang II (10
-7
M) activated MAPK kinase (by 30 and 70%) and the phosphorylation of ERK-1 and ERK-2 kinase (by 30% and by 40%), respectively. Activation of ERK-1 and ERK-2 occurred via a MEK kinase-dependent mechanism, since it was abolished by the MEK inhibitor PD-98059. No such effects of ADM were seen in cells from inner adrenocortical layers. The growth-promoting effect of ADM was unaffected by the PLA
2
inhibitor AACOCF3 (10
-5
M), the COX inhibitor indomethacin (10
-5
M) and the mixed COX/lipoxygenase (LOX) inhibitor phenidone (10
-5
M). In contrast, it was abolished by either the tyrosine kinase (TK) inhibitor tyrphostin-23 (10
-5
M) or by PD-98059 (10
4
M). Conclusions: 1) ADM exerts a mitogenic effect in the rat ZG, through ADM(22-52)-sensitive CGRP1 receptors; 2) this effect involves activation of the TKMAPK cascade, but not of the AC/PKA-, PLC/PKC-, and COX- or LOX-dependent signaling pathways.
Endothelial Dysfunction and Salt-Sensitive Hypertension in Spontaneously Diabetic Goto-Kakizaki Rats
Authors: Mervaala Eero Ma , Cheng Zhong Jiang , Vaskonen Timo , Tikkanen Ilkka , Karppanen Heikki , Muller Dominik N , Park Joon-Keun , Luft Friedrich C , Vapaatalo Heikki
Published: March 2022

P182

Dysfunction of vascular endothelium has been associated with several cardiovascular risk factors including hypertension, hypercholesterolemia, and congestive heart failure. We tested the hypothesis whether or not endothelial dysfunction also participates in the pathogenesis of spontaneously diabetic Goto-Kakizaki (GK) rats, an animal model for type 2 diabetes. Furthermore we evaluated the influence of high sodium diet (6 % NaCl w/w) and chronic AT1 receptor blockade (valsartan 10 mg/kg p.o. for 8 weeks starting at age 8 weeks). Compared to age-matched non-diabetic Wistar controls, GK rats had higher b-glucose levels (9.3±0.5 vs 6.9±0.2 mmol/l), 2.7-fold higher s-insulin levels, impaired glucose tolerance in oral glucose tolerance test, and moderately increased s-cholesterol and s-triglyserides levels (all variables p<0.05). Mean arterial blood pressure, measured by radiotelemetry, was 15 mm Hg higher in GK rats (p<0.01), whereas no difference in heart rate was observed. Heart weight- and kidney weight -to-body weight ratios were higher in GK rats (p<0.05), and 24-hour albuminuria was 1.5-fold. Endothelium-mediated vascular relaxation of noradrenaline-precontracted mesenteric arterial rings to acetylcholine was markedly impaired in GK rats compared to Wistar rats (p<0.05), whereas the endothelium-independent relaxations to sodium nitroprusside were similar in both strains. Semiquantitative scoring of ED-1 positive cells showed perivascular monocyte/macrophage infiltration in kidneys of GK rats. High sodium diet increased blood pressure in GK rats by 24 mm Hg, 24-hour albuminuria by 350 %, induced cardiac hypertrophy, and further impaired endothelium-dependent vascular relaxation (all variables p<0.05). Inflammatory cell response was also aggravated by high sodium diet. Chronic AT1 receptor blockade did not decrease blood pressure, but partially protected against albuminuria, inflammatory cell response, and endothelial dysfunction in salt-loaded GK rats. Our findings indicate that hypertension in diabetic GK rats is salt-sensitive and associated with endothelial dysfunction and perivascular inflammation.