Renal Artery Constriction Research Articles

NOX2 inhibition stabilizes vulnerable plaques by enhancing macrophage efferocytosis via MertK/PI3K/AKT pathway

NADPH oxidases 2 (NOX2) is the main source of ROS in macrophages, which plays a critical role in the formation of atherosclerosis. However, effects of NOX2 inhibition on established vulnerable plaques and the potential role involved remain unclear. The purpose of this study is to investigate the latent mechanism of NOX2-triggered vulnerable plaque development. We generated a vulnerable carotid plaque model induced by carotid branch ligation and renal artery constriction, combined with a high-fat diet in ApoE−/− mice. NOX2 specific inhibitor, GSK2795039 (10 mg/kg/day by intragastric administration for 8 weeks) significantly prevented vulnerable plaque, evaluated by micro-ultrasound imaging parameters. A profile of less intraplaque hemorrhage detection, increased collagen-lipid ratio, fibrous cap thickness and less necrotic core formation were also found in GSK2795039 treated group. Mechanistically, reduced 4-HNE, in situ lesional apoptosis and enhanced efferocytosis were involved in mice treated with NOX2 inhibitor. Further analysis in mouse macrophages confirmed the role of NOX2 inhibition in enhancing macrophage efferocytosis by regulating the MertK/PI3K/AKT pathway. In summary, our data defined previously few recognized roles of NOX2 in vulnerable plaque pathogenesis and an undescribed NOX2-ROS-MerTK axis acts involved in regulating macrophage efferocytosis in the formation of rupture-prone vulnerable plaques.

Heart rate fragmentation in renovascular hypertensive rats

Although rapid oscillations of the heart rate (HR) are attributed to vagal modulation of the heart, a pattern of ultra-rapid HR variation has been named heart rate fragmentation (HRF). It is a recently proposed approach to evaluate sino-atrial instability characterized by the presence of numerous inflections points in a series of successive values of cardiac intervals. HRF is increased in aging and coronary diseases. Hypertension markedly alters HRV indices and might affect HRF as well. This study aimed to investigate the HRF in renovascular hypertension in rats. Wistar rats were anesthetized, and hypertension was surgically induced by partial constriction of the left renal artery with a silver clip with a 0.2 mm gap. In one kidney one clip (1K1C) hypertension model, the contralateral kidney was removed. In two kidneys one clip (2K1C) model, the contralateral kidney was kept intact. Sham-operated control rats underwent to same surgical procedures without receiving the clip around the renal artery. After 45 days (2K1C) or 60 days (1K1C), animals were instrumented with a catheter into the femoral artery, and on the following day, their arterial pressure (AP) was directly recorded without the effect of anesthesia. For HRF analysis, pulse interval (PI) series were generated and transformed into a sequence of symbols “-1,” “0,” or “1” when the difference between successive PI values (transitions) was negative, zero, or positive, respectively. Following, sequences of 4 consecutive symbols were classified according to the number of transitions. The total percentage of inflection points (PIP) and the percentage of sequences with zero (W0), one (W1), two (W2), or three (W3) inflection points were quantified. As expected, the arterial pressure increased in both groups of hypertension rats compared to control counterparts. All HRF indices were found similar in 1K1C hypertensive rats compared to their control counterparts. Nevertheless, in 2K1C hypertensive rats HRF was found to be lower than normotensive controls (PIP: 64±7 vs. 79±1% and W2: 30±1 vs. 39±1% in 2K1C and normotensive controls, respectively). In conclusion, high blood pressure itself does not affect HRF, although, depending on the model of hypertension used, HRF can be markedly impaired. The interpretation of these findings is challenging, and the high levels of angiotensin in the 2K1C model may affect cardiac pacemaker cells, making their action potentials more stable than unstable. However, the specific mechanisms by which this could happen still need to be studied. Funding Sources: FAPESP, CAPES and CNPq This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Are Wistar Rats the Most Suitable Normotensive Controls for Spontaneously Hypertensive Rats to Assess Blood Pressure and Cardiac Structure and Function?

The first animal models of hypertension involved constriction of renal arteries (the Goldblatt kidney) or parenchyma (the Page kidney). Although these human analogs closely mimicked the pathophysiology of the disease, renovascular hypertension and the Page kidney represent only a small fraction of human hypertension. Most experimental studies of hypertension using animals have focused on understanding the mechanisms of primary hypertension. Models of primary hypertension have been more difficult to develop. Some models may have greater face validity than others with [...]

Protective Functions of Liver X Receptor α in Established Vulnerable Plaques: Involvement of Regulating Endoplasmic Reticulum-Mediated Macrophage Apoptosis and Efferocytosis.

BackgroundLiver X receptor (LXR) belongs to the metabolic nuclear receptor superfamily, which plays a critical regulatory role in vascular physiology/pathology. However, effects of systemic LXR activation on established vulnerable plaques and the potential isotype‐specific role involved remain unclear.Methods and ResultsThe 8‐week‐old male apolipoprotein E−/− mice went through carotid branch ligation and renal artery constriction, combined with a high‐fat diet. Plaques in the left carotid artery acquired vulnerable features 4 weeks later, confirmed by magnetic resonance imaging scans and histological analysis. From that time on, mice were injected intraperitoneally daily with PBS or GW3965 (10 mg/kg per day) for an additional 4 weeks. Treatment with LXR agonists reduced the lesion volume by 52.61%, compared with the vehicle group. More important, a profile of less intraplaque hemorrhage detection and necrotic core formation was found. These actions collectively attenuated the incidence of plaque rupture. Mechanistically, reduced lesional apoptosis, enhanced efferocytosis, and alleviated endoplasmic reticulum stress are involved in the process. Furthermore, genetic ablation of LXRα, but not LXRβ, blunted the protective effects of LXR on the endoplasmic reticulum stress–elicited C/EBP‐homologous protein pathway in peritoneal macrophages. In concert with the LXRα‐predominant role in vitro, activated LXR failed to stabilize vulnerable plaques and correct the acquired cellular anomalies in LXRα−/− apolipoprotein E−/− mice.ConclusionsOur results revealed that LXRα mediates the capacity of LXR activation to stabilize vulnerable plaques and prevent plaque rupture via amelioration of macrophage endoplasmic reticulum stress, lesional apoptosis, and defective efferocytosis. These findings might expand the application scenarios of LXR therapeutics for atherosclerosis.

Anthony Fairclough Lever

Anthony Fairclough Lever (“Tony”), who was the director and driving force of the Medical Research Council blood pressure unit in Glasgow, Scotland, between 1967 and 1994, and, latterly, professor emeritus...

Prostaglandin E2 regulates renal function in C57/BL6 mouse with 5/6 nephrectomy

AimsTo investigate the roles of cyclooxygenases (COX) and their metabolites in C57/BL6 mice with 5/6 nephrectomy, an animal model of chronic renal failure. Main methodsC57/BL6 mice were grouped into sham-operated (2K), one kidney removal (1K) and 5/6 nephrectomy groups (5/6Nx). Renal resistive index was measured by ultrasonography. Blood, aortae, renal arteries and renal cortex were collected for measurement of kidney function, assessment of vascular responsiveness, Western blotting, immuohistochemistry and enzyme-linked immunosorbent assays. Key findingsAfter four weeks, acetylcholine-induced relaxations were blunted in renal arteries of 1K and 5/6Nx mice; indomethacin, a non-selective COX inhibitor, improved the response in 5/6Nx, but not in 1K renal arteries. In 5/6Nx renal arteries, but not in 1K preparations, the protein presence of endothelial nitric oxide synthase (eNOS) was decreased, while that of COX-2 and its products [prostacyclin and thromboxane A2] were increased. The renal resistive index was lower in 5/6Nx mice, suggesting a lower resistance in the renal microvasculature. In the renal cortex of 5/6Nx mice, eNOS protein presence was increased; while the presence of COX-2 was not detectable. The prostaglandin E2 level was lower in the 5/6Nx cortex than in the other two groups. SignificanceThe early stage of renal mass removal is associated with increased renal arterial constriction and reduced microvascular resistance. The former is due to downregulation of eNOS and upregulation of COX-2, leading to an increased production of prostacyclin and thromboxane A2. A reduced production of PGE2 in the renal cortex is important for maintaining normal renal function.

Snakes and Hypertension.

Inhibition of Angiotensin Conversion in Experimental Renovascular Hypertension. By Miller ED Jr, Samuels A, Haber E, and Barger AC. Science 1972; 177:1108-9. Reprinted with permission from AAAS.Constriction of the renal artery and controlled reduction of renal perfusion pressure is followed by a prompt increase in systemic renin activity and a concomitant rise in blood pressure in trained, unanesthetized dogs. The elevated blood pressure induced by the renal artery stenosis can be prevented by prior treatment with the nonapeptide Pyr-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro, which blocks conversion of angiotensin I to angiotensin II. Further, the nonapeptide can restore systemic pressure to normal in the early phase of renovascular hypertension. These results offer strong evidence that the renin- angiotensin system is responsible for the initiation of hypertension in the unilaterally nephrectomized dog with renal artery constriction.

Abstract P141: GYY4137, a H 2 S Donor, Normalizes miR-132 Targeted Sirt1 and Ace2 Expression to Improve Kidney Function in Hypertension

MicroRNAs regulate several physiological processes and are implicated in various pathologies, including hypertension. Previous work indicates miR-132 targets Sirtuin 1 (Sirt1), a histone deacetylase and regulator of epigenetic gene silencing in various cellular processes. Sirt1 is expressed in the kidney; however, its role in hypertensive kidney and whether it is regulated by physiological gaseous molecules, such as hydrogen sulfide (H 2 S), is not known. In this study, we sought to determine the role of miR-132 in regulating Sirt1, Ace2 and At1 in hypertensive kidney and whether H 2 S donor, GYY4137 (GYY), could reverse these effects and mitigates renal dysfunction. Wild-type mice were treated without or with Ang-II (1000 ng/Kg/Min) and GYY (133 μM) for 4 weeks. Quantitative PCR, Western blot, and immunofluorescence assays were performed. Increased expression levels of miR-132 in hypertensive mice (3.79 fold vs control) were reduced in mice receiving GYY treatment (2.43 fold vs control). Sirt1 expression was reduced (-1.15 fold) in Ang-II mice but was upregulated in GYY (1.25 fold) and Ang-II+GYY (1.9 fold) groups. A similar effect was seen with Sirt1 protein where the expression was increased in animals treated with GYY and Ang-II+GYY (1.16, 1.03 respectively) compared to Ang-II (0.47). Ace2 in Ang-II+GYY (0.45) was increased compared to Ang-II (0.17), while At1 was reduced (0.46) compared to Ang-II (0.86). Immunofluorescence showed decreased signal of Sirt1 in the glomerulus in Ang-II mice and increased At1 in the blood vessels surrounding the glomerulus, leading to constriction of renal artery, decreased blood flow, and kidney dysfunction. These effects were alleviated in mice treated with GYY. Our data suggests that upregulation of miR-132 in hypertensive kidney decreases Sirt1 and Ace2 expression, leading to increased Ang-II signaling through the At1 receptor and GYY supplementation reverses these expression patterns, leading to increased blood flow and kidney function.

A forgotten chapter in the history of the renal circulation: the Josep Trueta and Homer Smith intellectual conflict.

This article reviews the pioneering and visionary contributions of the Catalan surgeon Josep Trueta (1897–1977) to the changes in renal circulation that contribute to the pathogenesis of acute renal failure (ARF). An erudite scientist with eclectic interests in physiology, orthopedics, politics, and medical history, Trueta's initial involvement in wound healing as a trauma surgeon during the Spanish Civil War and the London Blitz is what prompted him to postulate that a trauma-induced “neural effect” on the renal vasculature, with resultant renal arterial constriction could cause ARF. To test his hypothesis, Trueta assembled an experienced radiologist, a renowned physiologist, and a renal pathologist to study ARF in Oxford. They investigated the renal circulation of rabbits in response to diverse traumatic conditions by injecting a radio-opaque substance, using cine-radiography to visualize the flow of blood through the renal vasculature. Trueta's suggestion of renal cortical ischemia and diversion of blood to the less resistant medullary circulation (Trueta shunt) was criticized by Homer Smith and coworkers. In contrast to Homer Smith's data, which were derived from clearance studies and renal arteriovenous oxygen, Trueta used the diametrical opposite method of “direct” observation of the renal circulation. Their differing methodologies, direct visualization of the renal circulation as opposed to inferred computations from clearance studies, accounts for some of their conflicting theories. Nevertheless, the proposal of disparate renal flow compartments focused attention on intrarenal hemodynamics. Trueta's focus on renal cortical ischemia was ultimately validated by the studies of Barger in the dog and Hollenberg and Epstein in human subjects.

Altered myogenic vasoconstriction and regulation of whole kidney blood flow in the ASIC2 knockout mouse.

Previous studies from our laboratory have suggested that degenerin proteins contribute to myogenic constriction, a mechanism of blood flow regulation and protection against pressure-dependent organ injury, in renal vessels. The goal of the present study was to determine the importance of one family member, acid-sensing ion channel 2 (ASIC2), in myogenic constriction of renal interlobar arteries, myogenic regulation of whole kidney blood flow, renal injury, and blood pressure using ASIC2(+/+), ASIC2(+/-), and ASIC2(-/-) mice. Myogenic constriction in renal interlobar arteries was impaired in ASIC2(+/-) and ASIC2(-/-) mice, whereas constriction to KCl/phenylephrine was unchanged. Correction of whole kidney renal vascular resistance (RVR) during the first 5 s after a 10- to 20-mmHg step increase in perfusion pressure, a timeframe associated with myogenic-mediated correction of RVR, was slowed (4.2 ± 0.9, 0.3 ± 0.7, and 2.4 ± 0.3 resistance units/s in ASIC2(+/+), ASIC2(+/-), and ASIC2(-/-) mice). Although modest reductions in function were observed in ASIC2(-/-) mice, greater reductions were observed in ASIC2(+/-) mice, which may be explained by protein-protein interactions of ASIC2 with other degenerins. Isolated glomeruli from ASIC2(+/-) and ASIC2(-/-) mice had modest alterations in the expression of inflammation and injury markers (transforming growth factor-β, mouse anti-target of antiproliferative antibody-1, and nephrin), whereas ASIC2(+/-) mice had an increase in the remodeling marker collagen type III. Consistent with a more severe loss of function, mean arterial pressure was increased in ASIC2(+/-) mice (131 ± 3 mmHg) but not in ASIC2(-/-) mice (122 ± 3 vs. 117 ± 2 mmHg in ASIC2(+/+) mice). These results suggest that ASIC2 contributes to transduction of the renal myogenic response and are consistent with the protective role of myogenic constriction against renal injury and hypertension.

Abstract 188: Loss of Renal Prolyl Carboxypeptidase in Mice With Chronic Kidney Disease

There are 26 million adults with chronic kidney disease (CKD) in the U.S. and the incidence continues to increase. It is well documented that the activation of the renin angiotensin system and the elevated formation of angiotensin (Ang) II both contribute to renal pathophysiology in CKD. Emerging evidence suggests that the Ang II degrading protease prolyl carboxypeptidase (PCP) is renoprotective. Thus, we investigated protein expression and activity of renal PCP using immunofluorescence, western blot and mass spectrometry in a mouse model of CKD. Renal injury in male C57Bl6 mice was caused by constriction of the left renal artery using silver clips (2K1C-method). Blood pressure measurements by radiotelemetry revealed a significant increase of 36.1 ± 3.9 mm Hg in 2K1C animals compared with control animals 1 week after clip placement (p<0.0001). Using immunofluorescence and confocal microscopy, PCP was localized in the Bowman’s capsule of the glomerulus and in proximal and distal renal tubules. Western blot analysis showed PCP was significantly reduced in clipped 2K1C kidneys compared to unclipped kidneys of the 2K1C mice or compared to control mice (clipped 0.04 ± 0.02 vs unclipped 0.58 ± 0.16 vs control 0.65 ± 0.18, p < 0.05). In addition, renal PCP enzyme activity was found to be markedly reduced in 2K1C kidneys as assessed by mass spectrometric based enzyme assays (clipped 37.1 ± 4.3 pmol Ang-(1-7)/h/μg vs unclipped 77.3 ± 12.3 pmol Ang-(1-7)/h/μg vs control 120.7 ± 14.7 pmol Ang-(1-7)/h/μg, p < 0.01). In contrast, protein expression of prolyl endopeptidase, another enzyme capable of converting Ang II into Ang-(1-7), was not affected. Notably, renal pathologies were exacerbated in the 2K1C model as revealed by a significant increase in mesangial expansion (clipped 34.6 ± 3.1 vs unclipped 52.1 ± 4.0 vs control 1.2 ± 2.1, p < 0.0001) and renal fibrosis (clipped 57.5 ± 0.9 vs unclipped 33.0 ± 0.7 vs control 3.3 ± 0.2, p < 0.0001). Results suggest that PCP is suppressed in chronic kidney injury and that this downregulation may attenuate renoprotective effects via impaired Ang II degradation by PCP. Therefore, Ang II processing by PCP may have clinical implications in patients with renal pathologies.

Carotid Proliferative Plaque Formation in a Canine Model of Chronic Hypertension

BackgroundThere are few reports describing arterial plaque formation induced by hypertension alone. The aim of this study was to establish a canine model of chronic hypertension and investigate carotid plaque...

Vascular lesions induced by renal nerve ablation as assessed by optical coherence tomography: pre- and post-procedural comparison with the Simplicity® catheter system and the EnligHTN™ multi-electrode renal denervation catheter

AimsCatheter-based renal nerve ablation (RNA) using radiofrequency energy is a novel treatment for drug-resistant essential hypertension. However, the local endothelial and vascular injury induced by RNA has not been characterized, although this importantly determines the long-term safety of the procedure. Optical coherence tomography (OCT) enables in vivo visualization of morphologic features with a high resolution of 10–15 µm. The objective of this study was to assess the morphological features of the endothelial and vascular injury induced by RNA using OCT.Methods and resultsIn a prospective observational study, 32 renal arteries of patients with treatment-resistant hypertension underwent OCT before and after RNA. All pre- and post-procedural OCT pullbacks were evaluated regarding vascular changes such as vasospasm, oedema (notches), dissection, and thrombus formation. Thirty-two renal arteries were evaluated, in which automatic pullbacks were obtained before and after RNA. Vasospasm was observed more often after RNA then before the procedure (0 vs. 42%, P < 0.001). A significant decrease in mean renal artery diameter after RNA was documented both with the EnligHTN™ (4.69 ± 0.73 vs. 4.21 ± 0.87 mm; P < 0.001) and with the Simplicity® catheter (5.04 ± 0.66 vs. 4.57 ± 0.88 mm; P < 0.001). Endothelial-intimal oedema was noted in 96% of cases after RNA. The presence of thrombus formations was significantly higher after the RNA then before ablation (67 vs. 18%, P < 0.001). There was one evidence of arterial dissection after RNA with the Simplicity® catheter, while endothelial and intimal disruptions were noted in two patients with the EnligHTN™ catheter.ConclusionHere we show that diffuse renal artery constriction and local tissue damage at the ablation site with oedema and thrombus formation occur after RNA and that OCT visualizes vascular lesions not apparent on angiography. This suggests that dual antiplatelet therapy may be required during RNA.

Ang II induce kidney damage by recruiting inflammatory cells and up regulates PPAR gamma and Renin 1 gene: effect of β carotene on chronic renal damage

Antioxidants are widely used for prevention of diseases associated with oxidative stress and ischemic disorder. We investigated the hypothesis of antioxidants (α-tocopherol and β-carotene) can suppress the renal disorder in apo E-/-mice. Renal damage induced by chronic infusion of Angiotensin II (Ang II) into 4month old male apo E-/-mice. After that the mice were treated with diet enriched α tocopherol and β carotene (800mg/kg) for 150days. Ang II treated kidney showed polycystic appearance with accumulation of clear fluid and constriction of renal artery and renal vein was noticed. Vacuolar/cystic degeneration as well as inflammatory reactions was noticed in the tubules/glomerulus of Ang II treated mice. β carotene treated mice showed enormous numbers of regenerated tubules in the kidney and over expression of ICAM proteins in the regenerated tubules. CD 45.2, MAC 3 proteins were over expressed in the inflammatory cells infiltrated into the tubular region of Ang II treated kidney. Gene expression studies revealed up regulation of Renin 1 (Ren 1) and PPARγ genes in the kidney of Ang II treated animals, but the β carotene treatment controlled the expression of these genes in the regenerated kidneys. β carotene may have protective effective on chronic renal disorder. It may repress the inflammatory genes (Ren 1, PPARγ) to achieve the protective effect on Ang II induced renal damage.

Vascular smooth muscle function of renal glomerular and interlobar arteries predicts renal damage in rats

Previously, it was shown that individuals with good baseline (a priori) endothelial function in isolated (in vitro) renal arteries developed less renal damage after 5/6 nephrectomy (5/6Nx; Gschwend S, Buikema H, Navis G, Henning RH, de Zeeuw D, van Dokkum RP. J Am Soc Nephrol 13: 2909-2915, 2002). In this study, we investigated whether preexisting glomerular vascular integrity predicts subsequent renal damage after 5/6Nx, using in vivo intravital microscopy and in vitro myogenic constriction of small renal arteries. Moreover, we aimed to elucidate the role of renal ANG II type 1 receptor (AT1R) expression in this model. Anesthetized rats underwent intravital microscopy to visualize constriction to ANG II of glomerular afferent and efferent arterioles, with continuous measurement of blood pressure, heart rate, and renal blood flow. Thereafter, 5/6Nx was performed, interlobar arteries were isolated from the extirpated kidney, and myogenic constriction was assessed in a perfused vessel setup. Blood pressure and proteinuria were assessed weekly for 12 wk, and focal glomerulosclerosis (FGS) was determined at the end of study. Relative expression AT1R in the kidney cortex obtained at 5/6Nx was determined by PCR. Infusion of ANG II induced significant constriction of both afferent and efferent glomerular arterioles, which strongly positively correlated with proteinuria and FGS at 12 wk after 5/6Nx. Furthermore, in vitro measured myogenic constriction of small renal arteries negatively correlated with proteinuria 12 wk after 5/6Nx. Moreover, in vivo vascular reactivity negatively correlated with in vitro reactivity. Additionally, relative expression of AT1R positively correlated with responses of glomerular arterioles and with markers of renal damage. Both in vivo afferent and efferent responses to ANG II and in vitro myogenic constriction of small renal arteries in the healthy rat predict the severity of renal damage induced by 5/6Nx. This vascular responsiveness is highly dependent on AT1R expression. Intraorgan vascular integrity may provide a useful tool to guide the prevention and treatment of renal end-organ damage.

50 INFLUENCE OF EARLY LIFE VITAMIN D INSUFFICIENCY ON ARTERIAL PRESSURE AND VASCULAR AND RENAL FUNCTION

Background: Many women of reproductive age are vitamin D (VitD) deficient and the implications for the cardiovascular health of their offspring are unknown. The aim of this study was to examine the effects of in utero and early life VitD insufficiency in rats on cardiovascular and renal function in the offspring. Methods: Female Sprague-Dawley rats were fed either a VitD-deplete or –replete diet before, and throughout pregnancy and lactation. Offspring were maintained on the same diet as their mothers until 3 months of age, after which time, all rats were fed VitD replete diet. Conscious arterial pressure was measured at 2 and 12 months of age. Vascular function was assessed using myography and real-time PCR was used to examine renal gene expression of elements of the renin-angiotensin system (RAS). Kidney function was measured by clearance methods. Results: At 3 days postnatal renal mRNA expression of renin was reduced in VitD deficient males but not females. At 2 months VitD deficient offspring had elevated mean arterial pressure (MAP) and heart rate (HR) compared with controls. Mesenteric arteries exhibited endothelial vasodilator dysfunction. Following long term VitD repletion, renal RAS gene expression, MAP, HR and endothelial function had normalised. However, renal arteries had enhanced responsiveness to angiotensin II and perivascular nerve stimulation, and renal glomerular filtration rate was reduced by 40% (P<0.002). Conclusions: Early life VitD insufficiency causes transient increases in MAP and changes in renal RAS and endothelial function, but causes permanent changes in renal artery constriction and kidney function.

The Rho kinase inhibitor SAR407899 potently inhibits endothelin-1-induced constriction of renal resistance arteries

Increased renal vascular resistance contributes to the pathogenesis of hypertension. The new Rho kinase (ROCK) inhibitor SAR407899 more potently lowers arterial pressure than the commercially available ROCK inhibitor Y27623. We tested whether ROCK inhibition more effectively reduced agonist-induced vasoconstriction in renal than in nonrenal resistance arteries and if SAR407899 more potently inhibits agonist-induced vasoconstriction than Y27632. The effects of the ROCK inhibitors on endothelin-1 (ET-1) induced vasoconstriction were investigated in isolated renal and coronary arteries from lean, normotensive Dark Agouti and obese, type 2 diabetic Zucker diabetic fatty (ZDF) rats as well as in isolated human resistance arteries from the kidney and thymus. Vascular ROCK mRNA abundance was studied by real-time PCR (RT-PCR). ET-1-induced constriction depended more on ROCK in rat and human renal resistance arteries than in rat coronary or human thymic arteries, respectively. SAR407899 was more effective than Y27632 in reducing ET-1-induced vasoconstriction in ZDF rat renal resistance arteries. Maximum ET-1-induced vasoconstriction in SAR407899-treated and Y27632-treated human renal resistance arteries was 23 ± 5 and 48 ± 6% of control values, respectively. Transcripts of both ROCK isoforms were detected in rat and human renal resistance arteries. In human thymic arteries, only the ROCK2 transcript was found. ET-1-induced vasoconstriction is more ROCK-dependent in renal than in nonrenal resistance arteries. SAR407899 causes a greater inhibition of ET-1-induced vasoconstriction in renal resistance arteries from ZDF rats and patients than Y27632. The greater efficacy in renal vessels may contribute to the higher antihypertensive potency of SAR407899 compared with Y27632.

EXERCISE TRAINING INDUCES CHANGES IN THE RENIN‐ANGIOTENSIN SYSTEM TOWARDS ANG‐(1–7)/ACE2/MAS AXIS IN THE HYPOTHALAMUS OF RENOVASCULAR HYPERTENSIVE RATS

In the present study we evaluated angiotensin peptide levels, mRNA expression of angiotensin receptors, AT1 and MAS, and the enzymes, ACE and ACE2 in the hypothalamus (Hy) in renovascular hypertensive rats (2K1C) submitted to exercise training (ET). One week after renal artery constriction, animals started ET (swimming 60 min/day, 5 days/week). After 4 weeks, mean arterial pressure and heart rate (telemetry method) of 2K1C‐ET (122±6 mmHg and 349±5 beats/min; n=5) were lower in relation to 2K1C (157±3 mmHg and 361±5 beats/min; n=4). 2K1C showed an increase in AT1 expression and Ang II levels accompanied by a reduction in Ang‐(1–7) levels in Hy, which significantly reduced the Ang‐(1–7)/ Ang II levels (16±2 vs 40±10 in Sham). No changes in ACE or ACE2 were observed. ET induced in Hy an increase in ACE (2.4±0.3 au vs 1±0.1 au in Sham), ACE2 (3.7±0.4 au vs 1±0.1 au in Sham) and Mas (3.2±0.4 au vs 1±0.1 ua in Sham). These changes were accompanied by a reestablishment of Ang peptides ratio in the Hy. Our data show that ET may induce selective changes in the brain RAS favoring the ACE2/MAS axis, at least in the hypothalamus, suggesting a central site involved in the anti‐hypertensive effects induced by ET.

Effects of Potassium and Magnesium on Some Hemodynamic and Renal Function Related Parameters in 2k1c Hypertensive Rats

–The present study was done to investigate the effect of potassium and magnesium on aldosterone level, systolic blood pressure (SBP), heart rate (HR); renal function test parameters, serum nitric oxide (NO) and malondialdehyde (MDA) in 2-kidney, 1-clip (2K1C) hypertensive rats. The experimental rats were divided into six groups, each with seven rats and the treatments were continued for 4 weeks: Group 1: Control, Group 2: Sham operated surgery rats ,Group 3: 2K1C hypertensive rats , Group4: 2K1C + Potassium chloride ,KCl (80 gms/Kg diet) , Group5: 2K1C + Magnesium sulphate ,MgSO4 (80 gms/Kg diet), Group6: 2K1C +KCl+MgSO4 (160 gms/Kg diet). The results showed that renal artery constriction caused significant elevation in SBP and HR. Furthermore, serum levels of aldosterone, serum MDA, sodium ions (Na + ), chloride ions ( Cl ), creatinine and urine Na + levels were also elevated significantly in 2K1C hypertensive rats. On the other hand, administration of potassium decreased significantly SBP,HR, serum level of aldosterone, MDA, serum Na + and creatinine, while, serum levels of NO, K + and glomerular filtration rate (GFR) significantly increased compared with values in 2K1C hypertensive rats. Magnesium supplementation in 2K1C hypertensive rats caused significant decrease in SBP, HR, serum aldosterone level, serum MDA, Cl , calcium ions (Ca 2+ ) and increased serum levels of NO and magnesium ions (Mg 2+ ) levels compared with 2K1C hypertensive group. Moreover, administration of potassium in combination with magnesium in 2K1C hypertensive rats caused significant decrease in SBP, serum aldosterone level, HR, serum MDA, Na + , Cl , Ca 2+ , creatinine and serum levels of NO, K + , Mg 2+ and GFR were increased significantly, while, no significant change recorded in urine Na + levels compared all values with 2K1C hypertensive rats. Conclusion: The blood pressure lowering characteristic of potassium and magnesium was attributed to increase serum NO levels. The reduced serum MDA levels in hypertensive rats suggest that potassium and magnesium have antioxidant properties by reducing oxidative stress and preventing lipid peroxidation. Keywords––Potassium, Magnesium, Two-Kidney One-Clip hypertensive rats, Renin-angiotensin system,

Abstract 9717: Hypertension-Induced Atrial Remodeling Promotes Atrial Fibrillation Stabilization Upon Tachyarrhythmia Onset

Background: Hypertension (HT) is a major risk factor for atrial fibrillation (AF) but the underlying mechanisms are poorly understood. We hypothesized that HT produces an AF-stabilizing influence that favors faster progresion of spontaneous AF-maintenance when atrial tachyarrhythmia (AT) begins. Methods: HT was induced in dogs (n=6) by left nephrectomy and right renal artery constriction (1K1C). Sham operated dogs with the same surgery but no nephrectomy or artery constriction (n=5) were controls. Beginning 28 days from surgery, AT-pacing (ATP, 600 bpm) was started for 7 days. Serial atrial ERP measurement and AF induction was performed at days 7, 14, 28, 29, 30, 32 and 35 from surgery. Final open chest EPS was performed at day 36. Results: Systolic blood pressure (SBP) of HT dogs increased beginning at day 7 post 1K1C surgery (baseline 128±4 mm Hg; 7-d 183±6*, 28-d 176±10* mmHg; * p&lt;0.01 vs. baseline). SBP of sham dogs remained constant (baseline 133±4 mm Hg; 7-d 128±3, 28-d 126±6 mmHg). Mean AF duration (10 Hz burst pacing induced) increased marginally in HT dogs pre-ATP (Figure), but substantially after 1 and 2 days ATP vs control. At open-chest EPS, there were no differences in AF vulnerability to premature extrastimuli (HT, 69±5% vs. Sham, 70±11%; p=NS), AF duration (HT, 1501±273 sec vs. Sham, 1458±342 sec; p=NS) or regional ERP heterogeneity. HT dogs showed increased atrial conduction heterogeneity (heterogeneity index in HT, 2.01±0.10 vs. sham, 1.50±0.08; p&lt;0.01), associated with significant downregulation of connexin (Cx) 43 expression (by 57% + , + p&lt;0.05) but no change in Cx40 expression. Heart to body weight ratio increased in HT (9.7±0.4 vs. 8.5±0.2 + ), reflecting LVH. Conclusions: HT alone produces modest AF promotion, but changes caused by HT accelerate AF stabilization once initiated, increasing vulnerability to prolonged AF. The AF-promoting effects of hypertension are related to conduction abnormalities, possibly caused by connexin downregulation.