Non-treated Spontaneously Hypertensive Rats Research Articles

Cardioprotective effects of the proline-rich oligopeptide Bj-PRO-7a in spontaneously hypertensive rats.

The proline-rich oligopeptide from Bothrops jararaca snake venom, Bj-PRO-7a, promotes acute effects in blood pressure in hypertensive animals. However, the cardiac effects of this heptapeptide are completely unknown. Thus, we sought to evaluate whether the Bj-PRO-7a could protect against cardiac remodelling in spontaneously hypertensive rats (SHR). SHR were treated with Bj-PRO-7a (71nmol/kg/day, s.c.) or saline for 28days. Wistar rats were used as control. Systolic blood pressure (SBP) and heart rate (HR) were measured by tail-cuff plethysmography. Cardiomyocyte diameter and interstitial and perivascular fibrosis of the left ventricle (LV) were evaluated using Picrosirius staining. Immunofluorescence was used to detect collagen I and III. Fibroblast proliferation was assessed by immunohistochemistry to detect proliferating cell nuclear antigen (PCNA). Protein expression was assessed by western blot. The superoxide dismutase and catalase activities and the concentration of lipid peroxidation products were evaluated in the LV. The SBP and HR were not different between treated and non-treated SHR at the end of the treatment. However, Bj-PRO-7a attenuated the cardiomyocyte hypertrophy, deposition of interstitial and perivascular fibrosis and collagen I, and positive PCNA-labelled fibroblasts. This peptide also reduced the increased levels of TBARS, expression and activity of catalase, and activity of SOD in LV from SHR. Also, the Bj-PRO-7a increased the expression of metalloproteinases-2 in SHR hearts. These findings demonstrate that the Bj-PRO-7a reduced the pathological cardiac remodelling in a pressure-independent manner in hypertensive rats through mechanisms mediated by oxidative stress regulation.

Changes in the Urinary Metabolites in Losartan-Treated Spontaneously Hypertensive Rats

Introduction: This study examined the association of losartan induced changes in urinary metabolomic profile with the changes in blood pressure (BP) and renin-angiotensin- aldosterone system (RAAS) in spontaneously hypertensive rats (SHR). Methods: Male SHR were administered with either 0.5 mL of distilled water (control group, n=6) or 10 mg.kg -1 of losartan (group 2, n=6) daily by oral gavage for 4 weeks. Body weight, BP, food and water intake were measured weekly. At week 4, urine was collected for urinary electrolyte analysis and metabolite profiling, after which the animals were euthanised by decapitation and blood was collected for analysis of components of RAAS and electrolyte concentrations. Urine metabolite profile of SHR was determined using proton nuclear magnetic resonance ( 1 H-NMR) spectrometry combined with multivariate data analysis. Results: At week 4, losartan- treated SHR had significantly lower BP than non-treated SHR. There were no differences in water and food intake, body weight, serum and urinary electrolyte concentrations or in their urinary excretions between the two groups. No differences were evident in the components of RAAS except that the angiotensinogen level was significantly higher in losartan-treated SHR compared to non-treated SHR. Orthogonal partial least squares discriminant analysis (OPLS-DA) showed clear separation of urinary metabolites between control and losartan-treated SHR. Losartan-treated SHR group was separated from the control group by changes in the intermediates involved in glycine, serine and threonine metabolism. Conclusion: Antihypertensive effect of losartan in SHR seems to be associated with changes in urinary metabolite profile, particularly involving the metabolism of glycine, serine and threonine.

Comprehensive characterisation of phenolics from Nitraria sibirica leaf extracts by UHPLC-quadrupole-orbitrap- MS and evaluation of their anti-hypertensive activity

Ethnopharmacological relevanceFor more than ten scores years, the leaves and fruits of Nitraria sibirica have been used as a natural remedy for indigestion, irregular manes, and hypertension in the Middle East and Central Asia, especially, are recommended for hypertension treatment in the northwest region, China. Aim of the studywe aimed to support the traditional usage of N. sibirica leaves as pharmaceuticals or dietary supplements in treatment of hypertension by investigating their chemical constituents and anti-hypertensive activity. MethodsWe identified the chemical composition of N. sibirica leaves ethanolic purified extract (NSL-EPE) using UHPLC-quadrupole-orbitrap-MS, and quantified the main chemical constituents by an analytical method established and validated. We also evaluated anti-hypertensive activity of NSL-EPE using spontaneously hypertensive rats (SHR): blood pressure was measured weekly by non-invasive blood pressure (NIBP) measurements; hemodynamic parameters, biochemical and clinical chemistry variables in plasma, serum and kidney tissue were measured after 10 weeks of treatment with NSL-EPE as well. ResultsUHPLC-quadrupole-orbitrap-MS analysis identified 52 compounds, of which 40 compounds were reported for the first time in N. sibirica. 11 phenolic compounds further quantitatively analyzed, among which the most abundant compound was found to be clovin (8.8%). Systolic blood pressure decreased progressively from the second treatment week compared to that in non-treated SHRs. The plasma endothelin, aldosterone, angiotensin II levels were significantly increased, while the level of NOX was significantly decreased; glutathione to oxidized glutathione ratio, superoxide dismutase and total catalase levels in the kidney tissue were markedly accelerated, while malondialdehyde level was significantly reduced in NSL-EPE treated SHRs. Moreover, the serum cholesterol, triglyceride, blood uria nitrogen and creatinine were attenuated in NSL-EPE treated SHRs (P < 0.05), but in sharp contrast to those values in the water-treated SHRs. ConclusionThis study screened out leading compounds from N. sibirica and offered a new understanding of the antihypertensive properties of N. sibirica leaves, by which inhibit oxidative stress-induced endothelial dysfunction and improve lipid profiles.

Sildenafil reduces aortic endothelial dysfunction and structural damage in spontaneously hypertensive rats: Role of NO, NADPH and COX-1 pathways

Arterial hypertension is a condition associated with endothelial dysfunction, accompanied by an imbalance in the production of reactive oxygen species (ROS) and NO. The aim of this study was to investigate and elucidate the possible mechanisms of sildenafil, a selective phosphodiesterase-5 inhibitor, actions on endothelial function in aortas from spontaneously hypertensive rats (SHR).SHR treated with sildenafil (40 mg/kg/day, p.o., 3 weeks) were compared to untreated SHR and Wistar-Kyoto (WKY) rats. Systolic blood pressure (SBP) was measured by tail-cuff plethysmography and vascular reactivity was determined in isolated rat aortic rings. Circulating endothelial progenitor cells and systemic ROS were measured by flow cytometry. Plasmatic total antioxidant capacity, NO production and aorta lipid peroxidation were determined by spectrophotometry. Scanning electron microscopy was used for structural analysis of the endothelial surface.Sildenafil reduced high SBP and partially restored the vasodilator response to acetylcholine and sodium nitroprusside in SHR aortic rings. Using selective inhibitors, our experiments revealed an augmented participation of NO, with a simultaneous decrease of oxidative stress and of cyclooxygenase-1 (COX-1)-derived prostanoids contribution in the endothelium-dependent vasodilation in sildenafil-treated SHR compared to non-treated SHR. Also, the relaxant responses to sildenafil and 8-Br-cGMP were normalized in sildenafil-treated SHR and sildenafil restored the pro-oxidant/antioxidant balance and the endothelial architecture.In conclusion, sildenafil reverses endothelial dysfunction in SHR by improving vascular relaxation to acetylcholine with increased NO bioavailability, reducing the oxidative stress and COX-1 prostanoids, and improving cGMP/PKG signaling. Also, sildenafil reduces structural endothelial damage. Thus, sildenafil is a promising novel pharmacologic strategy to treat endothelial dysfunction in hypertensive states reinforcing its potential role as adjuvant in the pharmacotherapy of cardiovascular diseases.

Reduction of blood pressure elevation by losartan in spontaneously hypertensive rats through suppression of LARG expression in vascular smooth muscle cells

This study sought to elucidate the mechanism by which losartan inhibits blood pressure (BP) elevation in spontaneously hypertensive rats (SHRs). Four-week-old Wistar-Kyoto (WKY) rats and SHRs were either treated with losartan (20mg/kg/day) for 8 weeks or served as untreated controls. BP was measured by the tail-cuff method. At 12 weeks, isometric contraction of the aortic rings of the rats was evaluated with a force transducer and recorder. The mRNA and protein levels of the target Rho guanine nucleotide exchange factors (RhoGEFs), and the extent of myosin phosphatase target subunit 1 (MYPT-1) phosphorylation in the aorta, were determined using quantitative real-time polymerase chain reaction (qPCR) assay and Western blot analysis. The BP of the four-week-old SHRs did not differ from that of the age-matched WKY rats, whereas the BP of the twelve-week-old control group SHRs was higher than that of the control group WKY rats. Losartan treatment, however, inhibited BP elevation in both rat strains, doing so to a greater extent in the treatment group SHRs. The contractile force in response to angiotensin II of the aortic rings from the SHRs treated with losartan was significantly lower than that of the aortic rings from the non-treated SHRs. The protein expression of leukemia-associated RhoGEF (LARG) was significantly higher in the non-treated SHRs compared to the non-treated WKY rats. The study results showed that the reduction of BP elevation by losartan in SHRs occurs through the suppression of LARG expression and MYPT-1 phosphorylation in vascular smooth muscle cells.

A11010 Changes of extracellular matrix metalloproteinase-2 of isoproterenol injured normotensive and hypertensive rats are hampered by treatment with omega-3 fatty acids and melatonin

Objectives: Experimental and clinical studies suggest that melatonin and omega-3 fatty acids (PUFA) are cardioprotective, but underlying molecular mechanisms are still not fully explored. We hypothesize that both compounds may affect extracellular matrix remodeling by modulation of extracellular matrix metalloproteinases (MMP) activity. We aimed to explore MMP-2 activity in plasma, aorta and heart in normotensive and hypertensive rats after infarct-like cardiac injury induced by high dose of isoproterenol (ISO) as well as the effects of treatments with PUFA and melatonin. Methods: We used in our experiment Wistar (W) and spontaneously hypertensive rats (SHR) which were divided into four groups. 1)Controls without treatment; 2)Iso-injured rats (118 mg/kg totally, s.c./7days); 3)Iso-injured rats treated with melatonin (10 mg/kg, p.o., 2-mo); 4)Iso-injured rats treated with PUFA (Omacor, 1.68 g/kg, p.o.,2-mo). Samples from plasma, left and right ventricles and aorta were used to determine activity of MMP-2 by using gelatin zymography. Results: There was higher plasma but lower heart tissue-related MMP-2 activity in non-treated SHR vs W rats and no difference in aorta. ISO caused an increase of MMP-2 activity in plasma as well as in atria and decrease in left and right ventricles of W rats. In contrast, ISO decreased MMP-2 activity in plasma, aorta and increased in left and right ventricles of SHR. Melatonin and Omacor suppressed plasma MMP-2 activity in Iso-treated W but not in Iso-SHR. Both compounds lowered MMP-2 activity in atria of Iso-W rats but elevated in iso-SHR as well as decreased MMP-2 activity in ventricles of Iso-treated SHR only. Conclusion: Data indicates that both melatonin and Omacor modulate circulating and cardiovascular tissue-related MMP-2 activity. Supported:VEGA 2/0167/15, 2/0076/12; APVV-15-0119

A17051 LONG-TERM TOCOTRIENOL-RICH VITAMIN E SUPPLEMENTATION ACCELERATED THE DEVELOPMENT OF HIGH BLOOD PRESSURE IN SPONTANEOUSLY HYPERTENSIVE RATS

Objectives: This study hypothesized that TRE supplementation from pre-hypertensive stage diminishes renal oxidative stress and therefore prevents the development of hypertension in spontaneously hypertensive rats (SHR). This study aims to determine the effect of early TRE supplementation on (i) systolic blood pressure (SBP), (ii) renal superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and lipid peroxidation levels (TBARS) in SHR. Methods: Pre-hypertensive male SHR aged 4 weeks were given TRE (100 mg/kg body weight/day) via oral gavage for either 2, 4, 6, 8 or 12 weeks (TRE-SHR). Blood pressure and renal oxidant/antioxidant levels were determined at the end of supplementation i.e. at the age of 6, 8, 10, 12 and 16 weeks. SBP was measured using tail-cuff plethysmography. Statistical analysis was performed using one-way ANOVA followed by post-hoc Tukey's test. P < 0.05 was considered as statistically significant. Results: SBP of TRE-SHR was significantly lower at 6 weeks of age, but interestingly, it accelerated and was significantly higher at the age of 12 and 16 weeks compared to that in age-matched untreated SHR. TBARS levels were significantly lower in all the age groups in TRE-SHR. Renal GPx activity was significant higher in 6 weeks old TRE-SHR. No significant differences were evident in renal SOD and CAT activities in all the TRE-SHR groups when compared to those in the non-treated SHR. Conclusion: In conclusion, it appears that TRE supplementation to pre-hypertensive SHR initially delays the rise in systolic blood pressure but when given for a longer duration it increases the rate of increase in blood pressure; suggesting of its potential pro-hypertensive properties.

Effects of an ethanolic extract of mulberry fruit on blood pressure and vascular remodeling in spontaneous hypertensive rats

ABSTRACTMulberry (Morus alba) has been used in traditional oriental medicine since ages. Recently, it has been reported that mulberry produces hypotensive effects through the eNOS signaling pathway. However, the mechanism underlying the hypotensive effects of mulberry is not entirely clear. Moreover, the effects of mulberry on vascular remodeling events such as hyperplasia, an important etiology in the pathogenesis of hypertension and arteriosclerosis, are also ambiguous. Here, we hypothesized that an ethanolic extract of mulberry fruit (EMF) has beneficial effects on vascular remodeling and produces hypotensive effects. The effects of a 6-week oral administration of EMF were examined in spontaneously hypertensive rats (SHRs). The animals were divided into four groups: normotensive control (Wistar Kyoto rats), non-treated SHR, low-dose (100 mg/kg) EMF-treated SHR, and high-dose (300 mg/kg) EMF-treated SHR. Our results showed that the EMF-diet normalizes hypertension in SHRs in a dose-dependent manner, by preventing smooth muscle proliferation, thickening of the tunica media, and vascular hyper-reactivity. The endothelial functions were not substantially affected by the EMF diet in our experimental setting. In conclusion, we suggest that the mulberry fruit could act as a food supplement for reducing blood pressure in hypertensive subjects through its effects on smooth muscle proliferation and vascular contractility.

The role of losartan in preventing vascular remodeling in spontaneously hypertensive rats by inhibition of the H2O2/VPO1/HOCl/MMPs pathway

Vascular peroxidase 1 (VPO1) has been proved to be associated with vascular endothelial cell apoptosis by producing reactive oxygen species. However, the contribution of VPO1 to the development of vascular remodeling (VR) remains to be fully characterized. We explored the role of VPO1 in VR in spontaneously hypertensive rats (SHRs) and the underlying mechanism of losartan in inhibiting VR. Compared to Wistar-Kyoto (WKY) rats, the SHR showed remodeling of their vascular walls. The level of VPO1 and the hydrogen peroxide (H2O2) concentration were increased in the SHRs. However, the SHRs pretreated with losartan showed significant inhibition of blood pressure and VR and decreased levels of VPO1 and H2O2 compared to the non-treated SHRs. Angiotensin II significantly increased the expressions of MMP-2, MMP-9 and the concentrations of H2O2 and hypochlorous acid (HOCl) in vascular smooth muscle cells (VSMCs). However, only the H2O2 level increased in VSMCs when transfected with VPO1 shRNA. These results support a critical but previously unrecognized role of VPO1 in VR and suggest that therapies to reduce VPO1 may be novel approaches for VR.

PP.LB03.02] SIMVASTATIN IMPROVES MICROVASCULAR CEREBRAL BLOOD FLOW AND ATTENUATES ANGIOTENSIN II-INDUCED MICROCIRCULATORY CHANGES IN A HYPERTENSION MODEL

Objective: Statins may reduce blood pressure through a direct regulation of RAS and this study was designed to investigate the acute effects of simvastatin (SIM) on cerebral microcirculation and in spontaneously hypertensive rats (SHR), and the possible role of AT2 receptors on statins microvascular effects. Design and method: Male Wistar normotensive rats (WKY) and SHR were divided into 4 groups of 8 animals each: WKY-CTL and SHR-CTL treated with 0.9% saline solution, and WKY+sSIM and SHR+SIM treated with SIM 30 mg/kg/day during 3 days by gavage. We measured systolic blood pressure (SBP) and investigated brain functional capillary density (FCD) using intravital fluorescence videomicroscopy. Microvascular cerebral blood flow (mCBF) before and after local administration (cranial window) of Ang II (1 μM) was investigated using Laser Speckle Contrast Imaging, and the percentage of change on mCBF was calculated. Cerebral AT2 receptor expression was investigated by PCR. Results: SIM administration reduced SBP in SHR (SHR-CTL 203 ± 3 vs.SHR+SIM 172 ± 6 mmHg;p < 0.001). Cerebral FCD was reduced in hypertensive rats compared with normotensive rats (SHR-CTL 337 ± 61 vs. WKY-CTL 421 ± 35 capillaries/mm2; p < 0.05). The administration of SIM during 3 days induced a significant increase in cerebral FCD in hypertensive rats (SHR+SIM 530 ± 31 capillaries/ mm2;p < 0.05). The mCBF was reduced in SHR when compared with normotensive controls (SHR-CTL 185 ± 2 vs. WKY-CTL 231 ± 13 AU; p < 0.05) and SIM treatment was able to increase mCBF (SHR+SIM 208 ± 9 AU; p < 0.05) when compared with non-treated SHR (SHR-CTL). Locally applied, Ang II elicited a reduction in mCBF of hypertensive rats and an increase in normotensive rats (SHR-CTL -13.53 ± 2 % vs.WKY-CTL +13.74 ± 4%; p < 0,001), which was attenuated in hypertensive rats treated with SIM (SHR+SIM -6.7 ± 1%; p < 0,01vs.SHR-CTL). Additionally, AT2 receptor expression was reduced in the brain of SHR compared with WKY (SHR-CTL 0.5 ± 0.2 vs. WKY-CTL 1.5 ± 0.15 AT2R/GAPDH p < 0,05). Treatment of SHR with SIM increased brain expression of AT2 receptor (SHR+SIM 3.1 ± 0.9 AT2R/GAPDH;p < 0,05 vs.SHR-CTL). Conclusions: Acute treatment with SIM reversed cerebral microvascular rarefaction and restored microvascular cerebral blood flow of hypertensive rats. Furthermore, the increase in AT2 receptor expression might be associated with the positive pleiotropic effects of statins on cerebral microcirculation.

PS 10-04 HYPOTENSIVE EFFECT OF LOSARTAN THROUGH SUPPRESSING LEUKEMIA-ASSOCIATED RhoGEF EXPRESSION IN VASCULAR SMOOTH MUSCLE OF SPONTANEOUSLY HYPERTENSIVE RATS

Objective: To elucidate the mechanism that chronic blood pressure (BP) reduction caused by losartan is through the suppression of leukemia-associated Rho guanine nucleotide exchange factors (LARG) expression in vascular smooth muscle cells (VSMCs) of spontaneously hypertensive rats (SHRs). Design and Method: Four-week-old Wistar-Kyoto (WKY) rats and SHRs were treated with Losartan (20 mg/kg/day) for 8 weeks. BP was measured by the tail-cuff method. At 12 weeks, isometric contraction of rat aortic rings was measured with a force transducer and recorder. The target Rho guanine nucleotide exchange factors (RhoGEFs) messenger RNA (mRNA) and protein levels, and the myosin phosphatase target subunit 1 (MYPT-1) phosphorylation extent in aorta were determined using quantitative real-time polymerase chain reaction (qPCR) assay and Western blot analysis, respectively. Results: BP of four-week-old SHRs did not differ from that of age-matched WKY rats, whereas BP increased in twelve-week-old SHRs. Losartan treatment reduced BP in both rats’ strains, with greater extent in SHRs. The contractile force of aortic rings from SHRs treated with losartan was significantly lower than that from non-treated SHRs in response to angiotensin II. LARG protein expression was significantly higher in non-treated SHRs compared to WKY rats. After losartan treatment, both LARG protein level and phosphorylation extent of MYPT-1 were more suppressed in SHRs than in WKY rats. Conclusions: The study shows that chronic reduction of BP by losartan in SHRs is through suppressing LARG expression and MYPT-1 phosphorylation of VSMCs. Administration of losartan at early age of SHRs may help prevent hypertension development.

Effects of Kefir on the Cardiac Autonomic Tones and Baroreflex Sensitivity in Spontaneously Hypertensive Rats.

Aims: It has been previously shown that the probiotic kefir (a symbiotic matrix containing acid bacteria and yeasts) attenuated the hypertension and the endothelial dysfunction in spontaneously hypertensive rats (SHR). In the present study, the effect of chronic administration of kefir on the cardiac autonomic control of heart rate (HR) and baroreflex sensitivity (BRS) in SHR was evaluated.Methods: SHR were treated with kefir (0.3 mL/100 g body weight) for 60 days and compared with non-treated SHR and with normotensive Wistar-Kyoto rats. Cardiac autonomic vagal (VT) and sympathetic (ST) tones were estimated through the blockade of the cardiac muscarinic receptors (methylatropine) and the blockade of β1−adrenoceptor (atenolol). The BRS was evaluated by the tachycardia and bradycardia responses to vasoactive drug-induced decreases and increases in arterial blood pressure (BP), respectively. Additionally, spontaneous BRS was estimated by autoregressive spectral analysis.Results: Kefir-treated SHR exhibited significant attenuation of basal BP, HR, and cardiac hypertrophy compared to non-treated SHR (12, 13, and 21%, respectively). Cardiac VT and ST were significantly altered in the SHR (~40 and ~90 bpm) compared with Wistar rats (~120 and ~30 bpm) and were partially recovered in SHR-kefir (~90 and ~25 bpm). SHR exhibited an impaired bradycardic BRS (~50%) compared with Wistar rats, which was reduced to ~40% in the kefir-treated SHR and abolished by methylatropine in all groups. SHR also exhibited a significant impairment of the tachycardic BRS (~23%) compared with Wistar rats and this difference was reduced to 8% in the SHR-kefir. Under the action of atenolol the residual reflex tachycardia was smaller in SHR than in Wistar rats and kefir attenuated this abnormality. Spectral analysis revealed increased low frequency components of BP (~3.5-fold) and pulse interval (~2-fold) compared with Wistar rats and these differences were reduced by kefir-treatment to ~1.6- and ~1.5-fold, respectively. Spectral analysis also showed an impairment of spontaneous BRS in SHR, but kefir-treatment caused only a tendency to reverse this result.Conclusions: The novelty of this study is that daily chronic consumption of a low dose of kefir reduced the impairment of the cardiac autonomic control of HR and of the impaired BRS in SHR.

Chronic administration of the probiotic kefir improves the endothelial function in spontaneously hypertensive rats.

BackgroundThe beverage obtained by fermentation of milk with kefir grains, a complex matrix containing acid bacteria and yeasts, has been shown to have beneficial effects in various diseases. However, its effects on hypertension and endothelial dysfunction are not yet clear. In this study, we evaluated the effects of kefir on endothelial cells and vascular responsiveness in spontaneously hypertensive rats (SHR).MethodsSHR were treated with kefir (0.3 mL/100 g body weight) for 7, 15, 30 and 60 days and compared with non-treated SHR and with normotensive Wistar-Kyoto rats. Vascular endothelial function was evaluated in aortic rings through the relaxation response to acetylcholine (ACh). The balance between reactive oxygen species (ROS) and nitric oxide (NO) synthase was evaluated through specific blockers in the ACh-induced responses and through flow cytometry in vascular tissue.ResultsSignificant effects of kefir were observed only after treatment for 60 days. The high blood pressure and tachycardia exhibited by the SHR were attenuated by approximately 15 % in the SHR-kefir group. The impaired ACh-induced relaxation of the aortic rings observed in the SHR (37 ± 4 %, compared to the Wistar rats: 74 ± 5 %), was significantly attenuated in the SHR group chronically treated with kefir (52 ± 4 %). The difference in the area under the curve between before and after the NADPH oxidase blockade or NO synthase blockade of aortic rings from SHR were of approximately +90 and −60 %, respectively, when compared with Wistar rats. In the aortic rings from the SHR-kefir group, these values were reduced to +50 and −40 %, respectively. Flow cytometric analysis of aortic endothelial cells revealed increased ROS production and decreased NO bioavailability in the SHR, which were significantly attenuated by the treatment with kefir. Scanning electronic microscopy showed vascular endothelial surface injury in SHR, which was partially protected following administration of kefir for 60 days. In addition, the recruitment of endothelial progenitor cells was decreased in the non-treated SHR and partially restored by kefir treatment.ConclusionsKefir treatment for 60 days was able to improve the endothelial function in SHR by partially restoring the ROS/NO imbalance and the endothelial architecture due to endothelial progenitor cells recruitment.

Nicorandil ameliorates hypertension‐related bladder dysfunction in the rat

There is increasing evidence that ischemia is one of the main etiology in overactive bladder (OAB), and that nicorandil prevents OAB. We investigated the effect of nicorandil on hypertension-related bladder dysfunction in spontaneously hypertensive rats (SHRs). Twelve-week-old SHRs received six-weeks treatment with nicorandil (0, 3, or 10 mg/kg, i.p. every day). Wistar rats were used for normotensive controls. Six weeks after nicorandil treatment, the bladder blood flow was estimated by hydrogen clearance method, and the bladder functions were estimated by voiding behavior studies and functional studies. Tissue levels of nerve growth factor (NGF) were measured by ELISA method. Furthermore, the participation levels of K(ATP) channel pores were investigated by real-time PCR. SHRs showed significant increases in blood pressure, micturition frequency, tissue levels of NGF and expressions of both K(IR) 6.1 and K(IR) 6.2 mRNAs, and a significant decrease in the bladder blood flow. The carbachol-induced contractile responses were similar in all groups. Although both doses of nicorandil failed to decrease the blood pressure, nicorandil significantly decreased the micturition frequency, tissue levels of NGF and increased the bladder blood flow in a dose dependent manner. The expressions of K(IR) 6.1 and K(IR) 6.2 mRNAs were slightly up-regulated by the low dose of nicorandil, whereas the high dose of nicorandil significantly up-regulated those expressions compared to non-treated SHRs. These data indicate that nicorandil prevents hypertension-related bladder dysfunction in the SHR, which may be related to its effect on the increased blood flow in the bladder.

Long-Term Inhibition of Angiotensin Prevents Reduction of Periarterial Innervation of Calcitonin Gene-Related Peptide (CGRP)-Containing Nerves in Spontaneously Hypertensive Rats

The aim of this study was to investigate age-related changes in the density of calcitonin gene-related peptide (CGRP)-containing nerve fibers in spontaneously hypertensive rats (SHR) and the effects of long-term inhibition of the renin-angiotensin system on these changes. The density of immunocytochemically stained nerve fibers in the mesenteric artery was quantified by computer-assisted image processing. An age-related decrease in the density of CGRP-like immunoreactive (LI)-containing nerve fivers but not neuropeptide Y (NPY)-LI-containing sympathetic nerve fibers was found in the mesenteric artery of SHR but not Wistar Kyoto rats (WKY). The density of NPY-LI-containing sympathetic nerve fibers was significantly greater in SHR than in WKY. SHR were treated for 7 weeks with angiotensin converting enzyme inhibitor (0.005% temocapril), angiotensin II type-1 (AT1) receptor antagonist (0.025% losartan) or vasodilator (0.01% hydralazine) in their drinking water. Each drug treatment significantly lowered the systolic blood pressure measured by tail-cuff method. Long-term treatment of SHR with temocapril and losartan significantly increased the density of CGRP-LI-containing nerve fibers in mesenteric arteries. However, the density after hydralazine treatment was similar to the level in non-treated SHR. The density of NPY-LI-containing nerve fibers was not increased by any of the drug treatments. These results suggest that long-term inhibition of the renin-angiotensin system in SHR prevents remodeling of CGRPergic nerve fibers and prevents the reduction of CGRPergic nerve function.

Vasorelaxant effects of the chronic treatment with melatonin on mesenteric artery and aorta of spontaneously hypertensive rats.

To investigate the effect of a chronic treatment with melatonin on arterial pressure and a possible improvement of the vascular muscarinic and NO synthase (NOS) pathways in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Mean arterial pressure (MAP), systolic (SBP), diastolic blood pressure (DBP), and heart rate (HR) were evaluated in conscious rats treated with 30 mg/kg per day of melatonin during 4 weeks. Changes in MAP were evaluated following an intravenous injection of the NOS inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME). Relaxant effects of acetylcholine (Ach), sodium nitroprusside (SNP), and the calcium ionophore A23187 were examined on mesenteric beds and aortic rings with or without treatment with melatonin. Melatonin produced a significant reduction of MAP, SBP, DBP and HR in SHR (P < 0.05). L-NAME increased the MAP of melatonin-treated SHR by the same magnitude as that of WKY rats which was significantly higher than that of non-treated SHR (P< 0.05). Melatonin treatment improved the maximal relaxation of mesenteric arteries to A23187 in SHR (P < 0.001) to the WKY level and caused a slight increment in Ach- and A23187-induced vasodilations in aorta from SHR and WKY rats (P < 0.05). The present study showed that melatonin exerted a bradycardic and an antihypertensive action in SHR. The enhancement by melatonin of the endothelium-dependent vasodilation (Ach and/or A23187) in mesenteric artery and aorta from SHR and WKY rats and the higher increase in MAP following L-NAME treatment in melatonin-treated SHR suggest the contribution of an improved vascular NOS pathway activity in the hypotensive effect of melatonin.

Long-Term Treatment With Angiotensin Converting Enzyme Inhibitor Restores Reduced Calcitonin Gene-Related Peptide-Containing Vasodilator Nerve Function in Mesenteric Artery of Spontaneously Hypertensive Rats

Effects of long-term treatment with angiotensin converting enzyme (ACE) inhibitor on decreased function of calcitonin gene-related peptide (CGRP)-containing vasodilator nerves (CGRP nerves) in mesenteric resistance artery were investigated in spontaneously hypertensive rats (SHR). Eight-week-old SHR were treated for 7 weeks with 0.1% captopril, 0.01% temocapril, 0.05% pindolol or 0.005% hydralazine in drinking water. Long-term treatment with each drug significantly lowered mean blood pressure of SHR. In isolated and perfused mesenteric vascular beds with active tone, periarterial nerve stimulation (PNS) (0.5 to 8 Hz) produced frequency-dependent vasodilations, which were abolished by CGRP(8-37) (CGRP-receptor antagonist) and significantly smaller in SHR than in normotensive Wistar Kyoto rats. Treatment of SHR with captopril and temocapril but not with pindolol and hydralazine resulted in significantly greater PNS-induced vasodilation than in non-treated SHR, but ACE-inhibitor treatment did not affect vasodilation induced by exogenous CGRP. In captopril-treated SHR preparations, PNS evoked significantly larger CGRP-like immunoreactive release than in non-treated SHR. In non-treated 15-week-old SHR preparations, direct perfusion of captopril or temocapril (0.1 μM and 1 μM) did not modify frequency-dependent vasodilation in response to PNS. These results suggest that long-term ACE inhibitor treatment prevents or restores CGRP nerve function reduction in SHR.

Hypoglycemic and hypotensive effects of 6-cyclohexyl-2′- O-methyl-adenosine, an adenosine A 1 receptor agonist, in spontaneously hypertensive rat complicated with hyperglycemia

Metabolic and cardiovascular effects of 6-cyclohexyl-2′- O-methyl-adenosine (SDZ WAG 994), a selective and orally-active adenosine A 1 receptor agonist, were examined in spontaneously hypertensive rats (SHR) with hyperglycemia (SHR-DM). This model was made by the administration of streptozotocin (STZ; 60 mg/kg s.c.) to SHR 2 days after their birth. The serum glucose concentration and systolic/mean blood pressures (MBP) in 18–22-week-old rats were 14.7±0.8 mmol/l and 153±3/124±3 mmHg in SHR-DM, 13.7±0.3 mmol/l and 123±3/96±4 mmHg in normotensive with STZ (WKY-DM), 10.3±0.3 mmol/l and 165±1/136±3 mmHg in non-treated (without STZ) SHR, and 10.0±0.3 mmol/l and 115±3/90±4 mmHg in non-treated WKY. SDZ WAG 994 at 0.1 mg/kg p.o. lowered the serum glucose concentration, blood pressure and heart rate in SHR-DM. The effects were associated with the decrease in free fatty acid (FFA), triglyceride (TG), phospholipid (PL) and total cholesterol (TC) in serum of both SHR-DM and WKY-DM. On the contrary, the hypoglycemic effect was not found in WKY-DM, although the hypotensive effect was still observed. These data suggest that the risk factors for metabolic and cardiovascular complications in diabetes are reduced by SDZ WAG 994 through activation of adenosine A 1 receptors in adipocyte.

The Angiotensin l-Converting Enzyme Inhibitor, Cilazapril Inhibits the Platelet-Derived Growth Factor B Chain Expression in Glomeruli of Spontaneously Hypertensive Rats

To clarify whether in vivo expression of growth factors in the glomerulus is induced in a hypertensive animal model, we investigated the expression of platelet-derived growth factor (PDGF) B chain, transforming growth factor beta (TGF-beta), and angiotensin II (Ang II) type 1 receptors in glomeruli of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. We also investigated the effects of treatment with cilazapril, and angiotensin I-converting enzyme inhibitor, on this expression. First, the expression of PDGF B chain, TGF-beta, and Ang II receptors from the glomerulus were investigated using the reverse-transcriptase polymerase chain reaction in SHR and WKY rats. Although there was no significant difference in PDGF B chain, TGF-beta, and Ang II receptors from the glomerulus were investigated using the reverse-transcriptase polymerase chain reaction in SHR and WKY rats. Although there was no significant difference in PDGF B chain, TGF-beta or Ang II receptor expression between SHR and WKY rats at the age of 7 weeks, the PDGF B chain expression of 16-week-old SHR was significantly higher (4.4-fold) than that of age-matched WKY rats. Next, we administered oral cilazapril at a dose of 10 mg/kg to 13-week-old SHR daily for 3 weeks. The systolic blood pressure in SHR treated with cilazapril was significantly lower than that in control SHR. After administration of cilazapril for 3 weeks, we examined the in vivo expression of growth factors and Ang II receptors in the glomerulus. The PDGF B chain expression was suppressed by treatment with cilazapril (2.5-fold) as compared with nontreated SHR. No alteration in TGF-beta or Ang II receptor expression was detected. We did not find any histological changes in the kidneys of SHR, WKY rats or cilazapril-treated SHR, and cilazapril treatment did not suppress the glomerular size. These findings indicate that the expression of PDGF B chain in the glomerulus preceded the appearance of histological changes in SHR and that the administration of cilazapril inhibited the expression of PDGF B chain without affecting the glomerular size. This suggests that angiotensin I-converting enzyme inhibitors directly suppress the Ang II-induced PDGF B chain promotion in the glomerulus of SHR at the established hypertensive stage.

ANGIOTENSIN CONVERTING ENZYME INHIBITOR, CAPTOPRIL, INHIBITS CARDIAC HYPERTROPHY WITHOUT CHANGING COLLAGEN TYPES AND CONCENTRATION IN SPONTANEOUSLY HYPERTENSIVE RATS

1. The effects of the ACE inhibitor, captopril, on collagen metabolism in spontaneously hypertensive rats (SHR) with cardiac hypertrophy was examined. Captopril (100 mg/kg per day) was administered in drinking water to 20 week old male SHR for 12 weeks. Collagen concentration was calculated from hydroxyproline content, and relative proportions of types I, III and V collagen were determined by non-interrupted SDS-polyacrylamide gel electrophoresis (SDS-PAGE). These parameters were examined in age and sex matched Wistar-Kyoto (WKY) rats, as well as in non-treated SHR, and compared with those of captopril-treated SHR. 2. Captopril significantly reduced both blood pressure (191 +/- 12.1 vs 146 +/- 11.2 mmHg, P < 0.01), and the ratio of left ventricular (LV) weight to bodyweight (BW; 2.38 +/- 0.17 vs 2.05 +/- 0.12 mg/g, P < 0.01). There were no significant differences in collagen concentration among WKY rats, captopril-treated SHR and non-treated 32 week old SHR. However, total collagen content in captopril-treated SHR reduced significantly compared with non-treated 32 week old SHR (16.8 +/- 2.0 vs 21.3 +/- 0.8 mg, P < 0.01). The relative proportion of type V collagen was significantly higher in both captopril-treated (58.6 +/- 3.4 vs 46.8 +/- 1.3%, P < 0.01) and non-treated 32 week old SHR (59.9 +/- 3.1 vs 46.8 +/- 1.3%, P < 0.01) compared with WKY rats. However, there were no significant differences between captopril-treated SHR and non-treated 32 week old SHR.(ABSTRACT TRUNCATED AT 250 WORDS)