scholarly journals The role of aldosterone in mediating the dependence of angiotensin hypertension on IL-6

2009 ◽  
Vol 297 (6) ◽  
pp. R1742-R1748 ◽  
Author(s):  
LaShon C. Sturgis ◽  
Joseph G. Cannon ◽  
Derek A. Schreihofer ◽  
Michael W. Brands
Keyword(s):  
Blood Pressure ◽  
Mean Arterial Pressure ◽  
Early Stage ◽  
Mineralocorticoid Receptors ◽  
Ang Ii ◽  
Wild Type ◽  
Chronic Stimulation ◽  
Salt Hypertension ◽  
Stimulation Of

Knockout (KO) of IL-6 has been shown to attenuate ANG II hypertension, and mineralocorticoid receptors (MR) have been reported to contribute to the increase in IL-6 during acute ANG II infusion. This study determined whether that MR action is sustained with chronic ANG II infusion and whether it plays a role in mediating ANG II hypertension. ANG II infusion (90 ng/min) increased plasma IL-6 from 1.6 ± 0.6 to 22.7 ± 2.2 and 19.9 ± 3.2 pg/ml on days 7 and 14, respectively, and chronic MR blockade with spironolactone attenuated that only at day 7 (7.2 ± 2.2 pg/ml). ANG II increased MAP (19 h/day with telemetry) ∼40 mmHg, but in ANG II+spironolactone mice (25 or 50 mg·kg−1·day−1), mean arterial pressure (MAP) was not significantly different despite a tendency for lower pressure the first 6 days. To isolate further the mineralocorticoid link to IL-6 and blood pressure, DOCA-salt hypertension was induced in IL-6 KO and wild-type (WT) mice. Plasma IL-6 increased from 4.1 ± 1.7 to 34.5 ± 7.0 pg/ml by day 7 of DOCA treatment in the WT mice but was back to control levels by day 14. An IL-6 bioassay using the murine B9, B-cell hybridoma cell line demonstrated that plasma IL-6 measurements reflected actual IL-6 bioactivity. The hypertension was not different and virtually superimposable in WT vs. IL-6 KO mice, averaging 145 ± 2 and 144 ± 3 mmHg, respectively. Both experiments confirm chronic stimulation of IL-6 by mineralocorticoids but show that it is transient. In addition, IL-6 was not required for mineralocorticoid hypertension. This suggests that aldosterone contributes to the increase in plasma IL-6 in the early stage of ANG II hypertension but that the blood pressure actions of IL-6 in that model are linked most likely to ANG II rather than aldosterone.

Abstract 175: The Role of Axl in Accumulation of Immune Cells in Kidney and the Onset of Hypertension

Hypertension ◽  
2012 ◽  
Vol 60 (suppl_1) ◽  
Author(s):  
Sri Nagarjun Batchu ◽  
Angie Hughson ◽  
Janice Gerloff ◽  
Deborah J Fowell ◽  
Vyacheslav A Korshunov
Keyword(s):  
Blood Pressure ◽  
Immune Cells ◽  
Immune Cell ◽  
Kidney Injury ◽  
Wild Type ◽  
Protein Levels ◽  
Immune Cell Subsets ◽  
Early Increase ◽  
Salt Hypertension

Introduction: Gas6/Axl pathway contributes to elevation of blood pressure. Immune cells are implicated in initiation and maintenance of hypertension. In this study we aimed to investigate the role of Axl in immune cells on kidney injury and initiation of hypertension. Methods and Results: Deoxycorticosterone-acetate (DOCA; 75mg, 60days release) and salt hypertension was induced for 1wk or 6wks in four groups of Axl chimeras (n=4-5) that were generated by bone marrow (BM) transplant. Multi parameter flow cytometry was used to quantify five major immune cell subsets in digested kidneys from Axl chimeras. Systolic blood pressure (SBP) increased by 30mmHg in Axl+/+ →Axl+/+, Axl-/- →Axl-/- and Axl+/+ →Axl-/- mice after 1wk of DOCA-salt. However, chimeras that lack Axl in the BM cells (Axl-/- →Axl+/+) showed reduction in early increase in SBP (16+2mmHg). We observed a significant decrease in urine protein levels in Axl-/- →Axl+/+ (0.3+0.1μg/μl) compared to other Axl chimeras (∼0.7μg/μl) after 1wk of DOCA-salt. Kidney glomeruli areas were reduced in Axl-/- →Axl+/+ (4,143+229μm 2 ) compared to other Axl chimeras (∼6,000μm 2 ) after 6wks of DOCA-salt. Kidneys from Axl-/- →Axl-/- showed an increase in total leukocytes (8 vs. 4%), B cells (29 vs. 12%) and decrease in monocytes/macrophages (16 vs. 22%) and dendritic cells (5 vs. 10%) compared to Axl+/+ →Axl+/+. Moreover, Axl-/- →Axl+/+ showed further increase in leukocytes (17%), B (39%) and dendritic (13%) cells in kidneys compared to other Axl chimeras. In addition a small percentage of wild type T cells was increased in the kidneys from Axl-/- →Axl+/+ chimeras. Conclusions: These findings suggest that Axl expression in BM-derived cells is critical for kidney injury in DOCA-salt hypertension. Axl-dependent pathways regulate immune cell populations in the kidneys during initiation of hypertension. This study was supported by HL105623 grant (VAK)

Role of NOX2 in the regulation of afferent arteriole responsiveness

2009 ◽  
Vol 296 (1) ◽  
pp. R72-R79 ◽  
Author(s):  
Mattias Carlström ◽  
En Yin Lai ◽  
Zufu Ma ◽  
Andreas Patzak ◽  
Russell D. Brown ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Pressure ◽  
Renal Perfusion ◽  
Afferent Arteriole ◽  
Ang Ii ◽  
Wild Type ◽  
Simultaneous Application ◽  
Nitric Oxide Deficiency ◽  
Sensitizing Effect

NADPH oxidases (NOX) are the major source of reactive oxygen species (ROS) in the vasculature and contribute to the control of renal perfusion. The role of NOX2 in the regulation of blood pressure and afferent arteriole responsiveness was investigated in NOX2−/− and wild-type mice. Arteriole constrictions to ANG II (10−14–10−6 mol/l) were weaker in NOX2−/− compared with wild types. Nω-nitro-l-arginine methyl ester (l-NAME; 10−4 mol/l) treatment reduced basal diameters significantly more in NOX2−/− (−18%) than in wild types (−6%) and augmented ANG II responses. Adenosine (10−11–10−4 mol/l) constricted arterioles of wild types but not of NOX2−/−. However, simultaneous inhibition of adenosine type-2 receptors induced vasoconstriction, which was stronger in NOX2−/−. Adenosine (10−8 mol/l) enhanced the ANG II response in wild type, but not in NOX2−/−. This sensitizing effect by adenosine was abolished by apocynin. Chronic ANG II pretreatment (14 days) did not change the ANG II responses in NOX2−/−, but strengthened the response in wild types. ANG II pretreatment augmented the l-NAME response in NOX2−/− (−33%), but not in wild types. Simultaneous application of l-NAME and ANG II caused a stronger constriction in the NOX2−/− (−64%) than in wild types (−46%). Basal blood pressures were similar in both genotypes, however, chronic ANG II infusion elevated blood pressure to a greater extent in wild-type (15 ± 1%) than in NOX2−/− (8 ± 1%) mice. In conclusion, NOX2 plays an important role in the control of afferent arteriole tone and is involved in the contractile responses to ANG II and/or adenosine. NOX2 can be activated by elevated ANG II and may play an important role in ANG II-induced hypertension. NOX2-derived ROS scavenges nitric oxide, causing subsequent nitric oxide-deficiency.

gp91phox-containing NAD(P)H oxidase mediates attenuation of nitric oxide-dependent control of myocardial oxygen consumption by ANG II

2005 ◽  
Vol 289 (2) ◽  
pp. H862-H867 ◽  
Author(s):  
Shintaro Kinugawa ◽  
Juhua Zhang ◽  
Eric Messina ◽  
Erin Walsh ◽  
Harer Huang ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Oxygen Consumption ◽  
Myocardial Oxygen Consumption ◽  
Inflammatory Cells ◽  
Oxygen Electrode ◽  
No Production ◽  
Ang Ii ◽  
Wild Type ◽  
Stimulation Of

We have previously reported that ANG II stimulation increased superoxide anion (O2−) through the activation of NAD(P)H oxidase and inhibited nitric oxide (NO)-dependent control of myocardial oxygen consumption (MV̇o2) by scavenging NO. Our objective was to investigate the role of NAD(P)H oxidase, especially the gp91phox subunit, in the NO-dependent control of MV̇o2. MV̇o2 in mice with defects in the expression of gp91phox [gp91phox(−/−)] was measured with a Clark-type oxygen electrode. Baseline MV̇o2 was not significantly different between wild-type (WT) and gp91phox(−/−) mice. Stimulation of NO production by bradykinin (BK) induced significant decreases in MV̇o2 in WT mice. BK-induced reduction in MV̇o2 was enhanced in gp91phox(−/−) mice. BK-induced reduction in MV̇o2 in WT mice was attenuated by 10−8 mol/l ANG II, which was restored by coincubation with Tiron or apocynin. In contrast to WT mice, BK-induced reduction in MV̇o2 in gp91phox(−/−) mice was not altered by ANG II. There was a decrease in lucigenin (5 × 10−6 mol/l)-detectable O2− in gp91phox(−/−) mice compared with WT mice. ANG II resulted in significant increases in O2− production in WT mice, which was inhibited by coincubation with Tiron or apocynin. However, ANG II had no effect on O2− production in gp91phox(−/−) mice. Histological examination showed that the development of abscesses and/or the invasion of inflammatory cells occurred in lungs and livers but not in hearts and kidneys from gp91phox(−/−) mice. These results indicate that the gp91phox subunit of NAD(P)H oxidase mediates O2− production through the activation of NAD(P)H oxidase and attenuation of NO-dependent control of MV̇o2 by ANG II.

Role of the AT1A receptor in the CO2-induced stimulation of HCO3− reabsorption by renal proximal tubules

2007 ◽  
Vol 293 (1) ◽  
pp. F110-F120 ◽  
Author(s):  
Yuehan Zhou ◽  
Patrice Bouyer ◽  
Walter F. Boron
Keyword(s):  
Genetic Background ◽  
Proximal Tubules ◽  
Angiotensin Receptors ◽  
Ang Ii ◽  
Wild Type ◽  
Major Site ◽  
At1a Receptor ◽  
Reabsorption Rate ◽  
Stimulation Of

The proximal tubule (PT) is major site for the reabsorption of filtered HCO3−. Previous work on the rabbit PT showed that 1) increases in basolateral (BL) CO2 concentration ([CO2]BL) raise the HCO3− reabsorption rate ( JHCO3), and 2) the increase that luminal angiotensin II (ANG II) produces in JHCO3 is greatest at 0% [CO2]BL and falls to nearly zero at 20%. Here, we investigate the role of angiotensin receptors in the [CO2]BL dependence of JHCO3 in isolated perfused PTs. We found that, in rabbit S2 PT segments, luminal 10−8 M saralasin (peptide antagonist of ANG II receptors), lowers baseline JHCO3 (5% CO2) to the value normally seen at 0% in the absence of inhibitors and eliminates the JHCO3 response to changes in [CO2]BL. However, basolateral 10−8 M saralasin has no effect. As with saralasin, luminal 10−8 M candesartan (AT1 antagonist) reduces baseline JHCO3 and eliminates the [CO2]BL dependence of JHCO3. Luminal 10−7 M PD 123319 (AT2 antagonist) has no effect. Finally, we compared PTs from wild-type and AT1A-null mice of the same genetic background. Knocking out AT1A modestly lowers baseline JHCO3 and, like luminal saralasin or candesartan in rabbits, eliminates the JHCO3 response to changes in [CO2]BL. Our accumulated evidence suggests that ANG II endogenous to the PT binds to the apical AT1A receptor and that this interaction is critical for both baseline JHCO3 and its response to changes in [CO2]BL. Neither apical AT2 receptors nor basolateral ANG II receptors are involved in these processes.

Reactive Oxygen Species-Mediated Homologous Downregulation of Angiotensin II Type 1 Receptor Mrna by Angiotensin II

Hypertension ◽  
2000 ◽  
Vol 36 (suppl_1) ◽  
pp. 688-688
Author(s):  
Toshihiro Ichiki ◽  
Kotaro Takeda ◽  
Akira Takeshita
Keyword(s):  
Reactive Oxygen Species ◽  
Angiotensin Ii ◽  
Nadph Oxidase ◽  
Mrna Expression ◽  
Crucial Role ◽  
Oxygen Species ◽  
Ang Ii ◽  
Stimulation Of

58 Recent studies suggest a crucial role of reactive oxygen species (ROS) for the signaling of Angiotensin II (Ang II) through type 1 Ang II receptor (AT1-R). However, the role of ROS in the regulation of AT1-R expression has not been explored. In this study, we examined the effect of an antioxidant on the homologous downregulation of AT1-R by Ang II. Ang II (10 -6 mol/L) decreased AT1-R mRNA with a peak suppression at 6 hours of stimulation in rat aortic vascular smooth muscle cells (VSMC). Ang II dose-dependently (10 -8 -10 -6 ) suppressed AT1-R mRNA at 6 hours of stimulation. Preincubation of VSMC with N-acetylcysteine (NAC), a potent antioxidant, almost completely inhibited the Ang II-induced downregulation of AT1-R mRNA. The effect of NAC was due to stabilization of the AT1-R mRNA that was destabilized by Ang II. Ang II did not affect the promoter activity of AT1-R gene. Diphenylene iodonium (DPI), an inhibitor of NADH/NADPH oxidase failed to inhibit the Ang II-induced AT1-R mRNA downregulation. The Ang II-induced AT1-R mRNA downregulation was also blocked by PD98059, an extracellular signal-regulated protein kinase (ERK) kinase inhibitor. Ang II-induced ERK activation was inhibited by NAC as well as PD98059 whereas DPI did not inhibit it. To confirm the role of ROS in the regulation of AT1-R mRNA expression, VSMC were stimulated with H 2 O 2 . H 2 O 2 suppressed the AT1-R mRNA expression and activated ERK. These results suggest that production of ROS and activation of ERK are critical for downregulation of AT1-R mRNA. The differential effect of NAC and DPI on the downregulation of AT1-R mRNA may suggest the presence of other sources than NADH/NADPH oxidase pathway for ROS in Ang II signaling. Generation of ROS through stimulation of AT1-R not only mediates signaling of Ang II but may play a crucial role in the adaptation process of AT1-R to the sustained stimulation of Ang II.

Cardiac baroreflex dysfunction in patients with pulmonary arterial hypertension at rest and during orthostatic stress: Role of the peripheral chemoreflex

2021 ◽  
Author(s):  
Marcelle Paula-Ribeiro ◽  
Indyanara C. Ribeiro ◽  
Liliane C. Aranda ◽  
Talita M. Silva ◽  
Camila M. Costa ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Pulmonary Arterial Hypertension ◽  
Arterial Hypertension ◽  
Early Stage ◽  
Pressure Fluctuations ◽  
Sit To Stand ◽  
Peak Aerobic Capacity ◽  
Pulmonary Arterial ◽  
Peripheral Chemoreflex

The baroreflex integrity in early-stage pulmonary arterial hypertension (PAH) remains uninvestigated. A potential baroreflex impairment could be functionally relevant and possibly mediated by enhanced peripheral chemoreflex activity. Thus, we investigated 1) the cardiac baroreflex in non-hypoxemic PAH; 2) the association between baroreflex indexes and peak aerobic capacity (i.e., V̇O2peak); and 3) the peripheral chemoreflex contribution to the cardiac baroreflex. Nineteen patients and 13 age- and sex-matched healthy adults (HA) randomly inhaled either 100% O2 (peripheral chemoreceptors inhibition) or 21% O2 (control session), while at rest and during a repeated sit-to-stand maneuver. Beat-by-beat analysis of R-R intervals and systolic blood pressure provided indexes of cardiac baroreflex sensitivity (cBRS) and effectiveness (cBEI). The PAH group had lower cBEIALL at rest (mean ± SD: PAH = 0.5 ± 0.2 vs HA = 0.7 ± 0.1 a.u., P = 0.02) and lower cBRSALL (PAH = 6.8 ± 7.0 vs HA = 9.7 ± 5.0 ms mmHg-1, P < 0.01) and cBEIALL (PAH = 0.4 ± 0.2 vs HA= 0.6 ± 0.1 a.u., P < 0.01) during the sit-to-stand maneuver versus the HA group. The cBEI during the sit-to-stand maneuver was independently correlated to V̇O2peak (partial r = 0.45, P < 0.01). Hyperoxia increased cBRS and cBEI similarly in both groups at rest and during the sit-to-stand maneuver. Therefore, cardiac baroreflex dysfunction was observed under spontaneous and, most notably, provoked blood pressure fluctuations in non-hypoxemic PAH, was not influenced by the peripheral chemoreflex, and was associated with lower V̇O2peak suggesting it could be functionally relevant.

Abstract 12: The Role Of Memory Gamma Delta T Cells In Hypertension And Vascular Damage

Hypertension ◽  
2021 ◽  
Vol 78 (Suppl_1) ◽  
Author(s):  
Kevin D Comeau ◽  
Pierre Paradis ◽  
Ernesto L Schiffrin
Keyword(s):  
Blood Pressure ◽  
T Cells ◽  
Γδ T Cells ◽  
Effector Memory ◽  
Ang Ii ◽  
Mesenteric Lymph Nodes ◽  
Initial Exposure ◽  
Perivascular Adipose Tissue ◽  
Mild Hypertensive

Background: We recently demonstrated that γδ T cells participate in the pathogenesis of hypertension. Evidence also suggests that memory T cells may develop during an initial hypertensive episode, sensitizing mice to develop hypertension to further mild hypertensive challenges. However, whether memory γδ T cells develop and play a role in hypertension remains unknown. Our objective is to determine if memory γδ T cells sensitize mice to develop hypertension in response to a mild hypertensive challenge. Methods: Ten-12-week-old C57BL/6J mice were exposed or not to a hypertensive challenge (490 ng/kg/min angiotensin II (Ang II), SC) for two weeks, followed by a two-week washout period, and then infused with a subpressor dose of Ang II (140 ng/kg/min Ang II, SC) for two weeks. Blood pressure was measured via telemetry and central, effector, and resident memory γδ T cells were profiled by flow cytometry. Results: Mice exposed to the first hypertensive challenge had a higher systolic blood pressure than the sham group at the end of the subpressor hypertensive challenge (149±6 vs. 122±3 mmHg, P <0.001). After 14-days of Ang II infusion, effector memory γδ T cells increased 5.2-fold in the mesenteric artery perivascular adipose tissue (PVAT, 1.25±0.37% vs. 0.24±0.12%, P <0.05), and 1.8-fold in the mesenteric lymph nodes (mLN, 1.49±0.03% vs. 0.82±0.15%, P <0.05) compared to sham treated mice. After repeated Ang II infusion, central memory γδ T cells decreased by 57% in the aortic PVAT (6.79±1.46% vs. 15.69±2.87%, P <0.05), and by 22% in the mLN (0.18±0.01% vs. 0.23±0.01%, P <0.05) compared to control mice. Conclusion: An initial exposure to a hypertensive stimulus sensitizes mice to develop hypertension to a subsequent subpressor hypertensive challenge and results in the development of memory γδ T cells.

Abstract P059: A A Role of Aminopeptidase A in the Brain on Cardiovascular Regulation of Conscious Rat

Hypertension ◽  
2015 ◽  
Vol 66 (suppl_1) ◽  
Author(s):  
Takuto Nakamura ◽  
Masanobu Yamazato ◽  
Akio Ishida ◽  
Yusuke Ohya
Keyword(s):  
Blood Pressure ◽  
Protein Expression ◽  
Drinking Behavior ◽  
Cardiovascular Regulation ◽  
Ang Ii ◽  
Hypertensive Rats ◽  
Aminopeptidase A ◽  
The Brain

Objective: Aminopeptidase A (APA) have important role in conversion of Ang II to Ang III. Intravenous APA administration lowers blood pressure in hypertensive rats. In contrast, APA inhibition in the brain lowers blood pressure in hypertensive rats. Therefore APA might have different role on cardiovascular regulation. However, a role of APA and Ang III on cardiovascular regulation especially in the brain has not been fully understood. Our purpose of present study was to investigate a role of APA and Ang III in the brain on cardiovascular regulation in conscious state. Method: 12-13 weeks old Wistar Kyoto rat (WKY) and 12-16 weeks old spontaneously hypertensive rat (SHR) were used. i) APA distribution in the brain was evaluated by immunohistochemistry. Protein expression of APA was evaluated by Western blotting. Enzymatic activity of APA was evaluated using L-glutamic acid γ-(4-nitroanilide) as a substrate. ii) WKY received icv administration of Ang II 25ng/2μL and Ang III 25ng/2μL. We recorded change in mean arterial pressure (MAP) in conscious and unrestraied state and measured induced drinking time. iii) SHR received icv administeration of recombinant APA 400ng/4μL. We recorded change in MAP in conscious and unrestraied state and measured induced drinking time. Result: i) APA was diffusely immunostained in the cells of brain stem including cardiovascular regulatory area such as rostral ventrolateral medulla. Protein expression and APA activity in the brain were similar between WKY (n=3) and SHR (n=3).ii) Icv administration of Ang II increased MAP by 33.8±3.8 mmHg and induced drinking behavior for 405±90 seconds (n=4). Icv administration of Ang III also increased MAP by 24.7±2.4 mmHg and induced drinking behavior for 258±62 seconds (n=3). These vasopressor activity and induced drinking behavior was completely blocked by pretretment of angiotensin receptor type 1 blocker.iii) Icv administration of APA increased MAP by 10.0±1.7 mmHg (n=3). Conclusion: These results suggested that Ang III in the brain increase blood pressure by Angiotensin type 1 receptor dependent mechanism and APA in the brain may involved in blood pressure regulation as a vasopressor enzyme.

The effects of estradiol and testosterone on renal tissues oxidative after central injection of angiotensin II in female doca – salt treated rats

2018 ◽  
Vol 37 (3) ◽  
Author(s):  
Marzieh Kafami ◽  
Mahmoud Hosseini ◽  
Saeed Niazmand ◽  
Esmaeil Farrokhi ◽  
Mosa Al-Reza Hajzadeh ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Sex Hormones ◽  
Active Oxygen Species ◽  
Oxygen Species ◽  
Research Needs ◽  
Ang Ii ◽  
Detailed Mechanism ◽  
Female Wistar Rats

Abstract Background Although numerous studies have proven that estrogen (Est) has a protective effect on the development of hypertension, more research needs to be done to show its detailed mechanism in a variety of hypertension. The important role of active oxygen species in blood pressure is well defined. We examined whether or not sex hormones change the growth of reactive oxygen species (ROS) ‎in kidneys after central microinjection of angiotensin II (Ang II).‎ Materials and methods Female Wistar rats, 8 weeks old (200 ± 10 g) were used in this study. The animal groups were (1) Sham, (2) Ovariectomy (OVX), (3) Sham-Hypertension (Sham-Hyper), (4) OVX-Hypertension (OVX-Hyper), (5) Sham-Hyper-Est, (6) OVX-Hyper-Est‎;‎ (7) Sham-Hyper-Testosterone (Tst) and (8) OVX-Hyper-Tst. Solutions of 1% NaCl and 0.1 KCl ‎were used and desoxycorticostrone (doca-salt) was injected (45 mg/kg) 3 times a week in Hypertension groups. Estradiol and Tst (2 mg/kg and ‎5 mg/kg‎; daily; subcutaneously) for 4 weeks. Ang II (50 μM, 5 μL) was microinjected by intracerebroventricular ( i.c.v.) infusion and malondialdehyde (MDA) and thiol in the kidneys were measured. Results MDA in the kidneys was increased by Ang II and doca-salt treatments. Both estradiol and Tst decreased the kidney’s MDA. The level of thiol was higher in Hyper ‎groups and reversed after treatment with estradiol and Tst. Conclusions Our findings suggest that central effect of Ang II on blood pressure and kidney ‎disease is accompanied with increased levels of oxidative stress in the kidneys. Indeed sex hormones change the ROS level in the kidneys after central ‎microinjection of Ang II.‎‎

scholarly journals Proximal Tubule-Specific Deletion of Angiotensin II Type 1a Receptors in the Kidney Attenuates Circulating and Intratubular Angiotensin II–Induced Hypertension in PT- Agtr1a −/− Mice

Hypertension ◽  
2021 ◽  
Author(s):  
Xiao Chun Li ◽  
Ana Paula Oliveira Leite ◽  
Xiaowen Zheng ◽  
Chunling Zhao ◽  
Xu Chen ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Fusion Protein ◽  
Proximal Tubule ◽  
Proximal Tubules ◽  
Normal Blood ◽  
Ang Ii ◽  
Normal Blood Pressure ◽  
Wild Type ◽  
Induced Hypertension

The present study used a novel mouse model with proximal tubule-specific knockout of AT 1a receptors in the kidney, PT- Agtr1a −/− , to test the hypothesis that intratubular Ang II (angiotensin II) and AT 1a receptors in the proximal tubules are required for maintaining normal blood pressure and the development of Ang II–induced hypertension. Twenty-six groups (n=6–15 per group) of adult male wild-type, global Agtr1a −/− , and PT- Agtr1a −/− mice were infused with Ang II (1.5 mg/kg per day, IP), or overexpressed an intracellular Ang II fusion protein in the proximal tubules for 2 weeks. Basal telemetry blood pressure were ≈15±3 mm Hg lower in PT- Agtr1a −/− than wild-type mice and ≈13±3 mm Hg higher than Agtr1a −/− mice ( P <0.01). Basal glomerular filtration was ≈23.9% higher ( P <0.01), whereas fractional proximal tubule Na + reabsorption was lower in PT- Agtr1a −/− mice ( P <0.01). Deletion of AT 1a receptors in the proximal tubules augmented the pressure-natriuresis response ( P <0.01) and natriuretic responses to salt loading or Ang III infusion ( P <0.01). Ang II induced hypertension in wild-type, PT- Agtr1a −/− and PT- Nhe3 −/− mice, but the pressor response was ≈16±2 mm Hg lower in PT- Agtr1a −/− and PT- Nhe3 −/− mice ( P <0.01). Deletion of AT 1a receptors or NHE3 (Na + /H + exchanger 3) in the proximal tubules attenuated ≈50% of Ang II–induced hypertension in wild-type mice ( P <0.01), but blocked intracellular Ang II fusion protein-induced hypertension in PT- Agtr1a −/− mice ( P <0.01). Taken together, the results of the present study provide new insights into the critical role of intratubular Ang II/AT 1 (AT 1a )/NHE3 pathways in the proximal tubules in normal blood pressure control and the development of Ang II–induced hypertension.

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