Nitric Oxide Synthase in Spontaneously Hypertensive Rats

Since its discovery by Furchgott and Zawadzki in 1980 [18], endothelium-derived relaxing factor (EDRF) has been shown to play a central role in the cardiovascular system [10]. The endothelial product is chemically equivalent to nitric oxide (NO) [23, 40] or a biochemical congener thereof [48]. Fifteen years ago, this small, simple and highly toxic molecule was known as a lengthy list of environmental pollutants found in unsavory haunts such as smoke and smog, and even as destroyer of ozone, suspected carcinogen, and precursor of acid rain. In addition, NO seems an unlikely biological jack of all trades for most of the body's functions are regulated by extraordinarily large and complex proteins and compounds. But over the past decade, diverse lines of evidence have converged to show that this sometime poison is a fundamental player in the everyday business of the human body.     

Coupled Surface Plasmon-Polariton Modes of Metallic Single-Walled Carbon Nanotubes

The propagation of the coupled surface plasmon-polariton modes in the metallic single-walled carbon nanotubes are investigated, taking into account the retardation effects. A simple model based on the classical electrodynamics and the two-fluid hydrodynamic theory is proposed. The dispersion relation of the surface polariton modes is obtained in order to survey the effects of the two-fluid model and the insulating dielectric media.     

Proteomic Response to Acupuncture Treatment in Spontaneously Hypertensive Rats

Previous animal and clinical studies have shown that acupuncture is an effective alternative treatment in the management of hypertension, but the mechanism is unclear. This study investigated the proteomic response in the nervous system to treatment at the Taichong (LR3) acupoint in spontaneously hypertensive rats (SHRs). Unanesthetized rats were subject to 5-min daily acupuncture treatment for 7 days. Blood pressure was monitored over 7 days. After euthanasia on the 7^th day, rat medullas were dissected, homogenized, and subject to 2D gel electrophoresis and MALDI-TOF analysis. The results indicate that blood pressure stabilized after the 5th day of acupuncture, and compared with non-acupoint treatment, Taichong-acupunctured rat’s systolic pressure was reduced significantly (P<0.01), though not enough to bring blood pressure down to normal levels. The different treatment groups also showed differential protein expression: the 2D images revealed 571±15 proteins in normal SD rats’ medulla, 576±31 proteins in SHR’s medulla, 597±44 proteins in medulla of SHR after acupuncturing Taichong, and 616±18 proteins in medulla of SHR after acupuncturing non-acupoint. In the medulla of Taichong group, compared with non-acupoint group, seven proteins were down-regulated: heat shock protein-90, synapsin-1, pyruvate kinase isozyme, NAD-dependent deacetylase sirtuin-2, protein kinase C inhibitor protein 1, ubiquitin hydrolase isozyme L1, and myelin basic protein. Six proteins were up-regulated: glutamate dehydrogenase 1, aldehyde dehydrogenase 2, glutathione S-transferase M5, Rho GDP dissociation inhibitor 1, DJ-1 protein and superoxide dismutase. The altered expression of several proteins by acupuncture has been confirmed by ELISA, Western blot and qRT-PCR assays. The results indicate an increase in antioxidant enzymes in the medulla of the SHRs subject to acupuncture, which may provide partial explanation for the antihypertensive effect of acupuncture. Further studies are warranted to investigate the role of oxidative stress modulation by acupuncture in the treatment of hypertension.     

Heterogeneity in Arterial Remodeling among Sublines of Spontaneously Hypertensive Rats

Objectives

Spontaneously hypertensive rats (SHR) have been used frequently as a model for human essential hypertension. However, both the SHR and its normotensive control, the Wistar Kyoto rat (WKY), consist of genetically different sublines. We tested the hypothesis that the pathophysiology of vascular remodeling in hypertension differs among rat sublines.

Methods and Results

We studied mesenteric resistance arteries of WKY and SHR from three different sources, at 6 weeks and 5 months of age. Sublines of WKY and SHR showed differences in blood pressure, body weight, vascular remodeling, endothelial function, and vessel ultrastructure. Common features in small mesenteric arteries from SHR were an increase in wall thickness, wall-to-lumen ratio, and internal elastic lamina thickness.

Conclusions

Endothelial dysfunction, vascular stiffening, and inward remodeling of small mesenteric arteries are not common features of hypertension, but are subline-dependent. Differences in genetic background associate with different types of vascular remodeling in hypertensive rats.     

Egg-Derived Tri-Peptide IRW Exerts Antihypertensive Effects in Spontaneously Hypertensive Rats

Background

There is a growing interest in using functional food components as therapy for cardiovascular diseases such as hypertension. We have previously characterized a tri-peptide IRW (Ile-Arg-Trp) from egg white protein ovotransferrin; this peptide showed anti-inflammatory, anti-oxidant and angiotensin converting enzyme (ACE) inhibitor properties in vitro. Given the pathogenic roles played by angiotensin, oxidative stress and inflammation in the spontaneously hypertensive rat (SHR), we tested the therapeutic potential of IRW in this well-established model of hypertension.

Methods and Results

16–17 week old male SHRs were orally administered IRW at either a low dose (3 mg/Kg BW) or a high dose (15 mg/Kg BW) daily for 18 days. Blood pressure (BP) and heart rate were measured by telemetry. Animals were sacrificed at the end of the treatment for vascular function studies and measuring markers of inflammation. IRW treatment attenuated mean BP by ~10 mmHg and ~40 mmHg at the low- and high-dose groups respectively compared to untreated SHRs. Heart rate was not affected. Reduction in BP was accompanied by the restoration of diurnal variations in BP, preservation of nitric oxide dependent vasorelaxation, as well as reduction of plasma angiotensin II, other inflammatory markers and tissue fibrosis.

Conclusion

Our results demonstrate anti-hypertensive effects of IRW in vivo likely mediated through ACE inhibition, endothelial nitric oxide synthase and anti-inflammatory properties.     

Vasodilating Effect of Di-Peptides in Thoracic Aortas from Spontaneously Hypertensive Rats

In this study, we found that antihypertensive di-peptide Val-Tyr (VY) showed a vascular relaxation effect in KCl-induced contraction of thoracic aorta rings from 18-week-old spontaneously hypertensive rats among di-peptides of VY, Ile-Tyr, and Tyr-Val irrespective of their angiotensin I-converting enzyme inhibitory activity. The effect was endothelium-independent, and was closely associated with vascular responses in the vascular smooth muscle layer.     

The Effect of DNA-Dispersed Single-Walled Carbon Nanotubes on the Polymerase Chain Reaction

The unique properties of single-wall carbon nanotubes (SWCNT) make them useful in many new technologies and applications. The interaction of DNA and SWCNT is of interest for many uses, including molecular sensors. This study determined polymerase chain reaction (PCR) efficiency in amplifying a 76 base pair DNA sequence in the presence of SWCNT, of heterogeneous “Mix” and (6,5)-enriched chiralities, associated with three DNA sequences. The dependence of PCR efficiency on the concentration of DNA:SWCNT preparations was measured, as well as their age and level of dispersion (less than one month or between four and ten months). Additionally, the ability to directly amplify the DNA sequence associated with the SWCNT scaffold was investigated. In PCRs with DNA:SWCNT preparations less than one month old, concentrations greater than or equal to 0.1 mg/mL inhibited the PCR reaction. In PCRs with older preparations, no inhibition was seen at 0.01 or 0.1 mg/mL, with amplification at 1 mg/mL in some samples. Additionally, our studies showed that the DNA directly associated with the SWCNT can be amplified using PCR. This work provides an inhibitory concentration of DNA-dispersed SWCNT in PCR reactions for different preparations as well as a basis for future DNA:SWCNT studies that require PCR amplification. This will be useful for future studies focused on the use of SWCNT in molecular sensing technologies.     

Therapeutic Vaccines against Human and Rat Renin in Spontaneously Hypertensive Rats

Vaccination provides a promising approach for treatment of hypertension and improvement in compliance. As the initiation factor of renin-angiotensin system, renin plays a critical role in hypertension. In this study, we selected six peptides (rR32, rR72, rR215, hR32, hR72, and hR215) belonging to potential epitopes of rat and human renin. The main criteria were as follows: (1) include one of renin catalytic sites or the flap sequence; (2) low/no-similarity when matched with the host proteome; (3) ideal antigenicity and hydrophilicity. The peptides were coupled to keyhole limpet hemocyanin and injected into SpragueDawley (SD) rats, spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats. The antisera titers and the binding capacity with renin were detected. The effects of the anti-peptides antibodies on plasma renin activity (PRA) and blood pressure were also determined. All peptides elicited strong antibody responses. The antisera titers ranged from 1:32,000 to 1:80,000 in SD rats on day 63. All antisera could bind to renin in vitro. Compared with the control antibody, the antibodies against the rR32, hR32, rR72 and hR72 peptides inhibited PRA level by up to about 50%. Complete cross-reactivity of the anti-rR32 antibody and the anti-hR32 antibody was confirmed. The epitopes rR32 and hR32 vaccines significantly decreased systolic blood pressure (SBP) of SHRs up to 15mmHg (175±2 vesus 190±3 mmHg, P = 0.035; 180±2 vesus 195±3 mmHg, P = 0.039), while no obvious effect on SD rats. Additionally, no significant immune-mediated damage was detected in the vaccinated animals. In conclusion, the antigenic peptide hR32 vaccine mimicking the ³²Asp catalytic site of human renin may constitute a novel tool for the development of a renin vaccine.     

Angiotensin-Converting Enzyme Activity Is Reduced in Brain Microvessels of Spontaneously Hypertensive Rats

Abstract: Angiotensin-converting enzyme (ACE) activity in brain microvessels of spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) controls was measured. Cerebral microvessels, prepared from the cerebral cortices by the albumin flotation and glass bead filtration technique, were free of neuronal and glial elements. ACE activity in brain microvessels of SHR was lower than that of WKY. A Woolf-Augustinsson-Hofstee plot showed that the reduction of the enzyme activity in SHR was due to a 30% decrease in V_max without any change in K_m for substrate. The decrease of ACE activity in brain micro-vessels of SHR may indicate an impairment of the central renin-angiotensin system and may be related to cerebral microvascular dysfunctions occurring in hypertension.     

Antihypertensive Effects of Acetic Acid and Vinegar on Spontaneously Hypertensive Rats

To clarify the possibility of a preventive effect of dietary vinegar on blood pressure, long-term administration of vinegar or the acetic acid to SHR was examined. As a result, it was observed that acetic acid itself, the main component of vinegar, significantly reduced both blood pressure (p<0.05) and renin activity (p<0.01) compared to controls given no acetic acid or vinegar, as well as vinegar. There were no significant differences in angiotensin I-converting enzyme activity in various organs. As for the mechanism of this function, it was suggested that this reduction in blood pressure may be caused by the significant reduction in renin activity and the subsequent decrease in angiotensin II. From this study, it was also suggested that the antihypertensive effect of vinegar is mainly due to the acetic acid in it.     

Receptor Adaptive Responsiveness in Disease Models: 6-Ohda Lesioned and Spontaneously Hypertensive Rats

Abstract

We have examined the adaptive modifications of brain monoamine receptors in response to pathophysiological processes in animal disease models: 6-OHDA lesioned and spontaneously hypertensive rats (SHR).

The two models share a similar increase in D-1 receptor densities, while noradrenergic receptors are affected in different way: α;-1 and β are supersensitive in 6-OHDA lesioned rats and only α;-2 are increased in SHR. S-1 receptors too are up-regulated in SHR. We must notice that though receptor hypersensitivity in the 6-OHDA model is linked to massive decreases in neurotransmitter levels, this mechanism seems not to exist in the SHR model.     

Atrial Arrhythmia in Ageing Spontaneously Hypertensive Rats: Unraveling the Substrate in Hypertension and Ageing

Background

Both ageing and hypertension are known risk factors for atrial fibrillation (AF) although the pathophysiological contribution or interaction of the individual factors remains poorly understood. Here we aim to delineate the arrhythmogenic atrial substrate in mature spontaneously hypertensive rats (SHR).

Methods

SHR were studied at 12 and 15 months of age (n = 8 per group) together with equal numbers of age-matched normotensive Wistar-Kyoto control rats (WKY). Electrophysiologic study was performed on superfused isolated right and left atrial preparations using a custom built high-density multiple-electrode array to determine effective refractory periods (ERP), atrial conduction and atrial arrhythmia inducibility. Tissue specimens were harvested for structural analysis.

Results

Compared to WKY controls, the SHR demonstrated: Higher systolic blood pressure (p<0.0001), bi-atrial enlargement (p<0.05), bi-ventricular hypertrophy (p<0.05), lower atrial ERP (p = 0.008), increased atrial conduction heterogeneity (p = 0.001) and increased atrial interstitial fibrosis (p = 0.006) & CD68-positive macrophages infiltration (p<0.0001). These changes resulted in higher atrial arrhythmia inducibility (p = 0.01) and longer induced AF episodes (p = 0.02) in 15-month old SHR. Ageing contributed to incremental bi-atrial hypertrophy (p<0.01) and atrial conduction heterogeneity (p<0.01) without affecting atrial ERP, fibrosis and arrhythmia inducibility. The limited effect of ageing on the atrial substrate may be secondary to the reduction in CD68-positive macrophages.

Conclusions

Significant atrial electrical and structural remodeling is evident in the ageing spontaneously hypertensive rat atria. Concomitant hypertension appears to play a greater pathophysiological role than ageing despite their compounding effect on the atrial substrate. Inflammation is pathophysiologically linked to the pro-fibrotic changes in the hypertensive atria.     

Antihypertensive Effect of an Extract of Passiflora edulis Rind in Spontaneously Hypertensive Rats

Orally administered methanol extract of Passiflora edulis rind (10 mg/kg or 50 mg/kg) or luteolin (50 mg/kg), which is one of consistent polyphenols of the extract, significantly lowered systolic blood pressure in spontaneously hypertensive rats (SHRs). Quantitative analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS) showed that the extract contained 20 μg/g dry weight of luteolin and 41 μg/g dry weight of luteolin-6-C-glucoside. It also contained γ-aminobutyric acid (GABA, 2.4 mg/g dry weight by LC-MS/MS or 4.4 mg/g dry weight by amino acid analysis) which has been reported to be an antihypertensive material. Since the extract contained a relatively high concentration of GABA, the antihypertensive effect of the extract in SHRs might be due mostly to the GABA-induced antihypertensive effect and partially to the vasodilatory effect of polyphenols including luteolin.     

Antihypertensive Effects of Peptides in Autolysate of Bonito Bowels on Spontaneously Hypertensive Rats

An autolysate of bonito bowels was treated with ultrafiltration, loose R0 concentration, ion-exchange chromatography, and reverse phase chromatography to increase its potency to inhibit angiotensin I-converting enzyme (ACE) activity by 16-fold. Oral administration of the partially purified autolysate decreased the systolic blood of spontaneously hypertensive rats (SHR) in a dose-dependent manner at the doses of 1g peptides/kg or higher. The relationship between the antihypertensive activity (in vivo) of the partially purified preparation and its ACE inhibitory activity (in vitro) in comparison with previously reported ACE inhibitory peptides is discussed.     

Low Activity of Angiotensin-Converting Enzyme in Cerebral Microvessels of Young Spontaneously Hypertensive Rats

Angiotensin-converting enzyme (ACE) activity was measured in microvessels prepared from cerebral cortices of 4-week-old spontaneously hypertensive rats (SHR). The Vmax value of the ACE activity in the cerebral microvessels of SHR was lower than that of Wistar Kyoto controls of the same age by 25% without difference in Km value for substrate. The low activity of ACE in the cerebral microvessels of young SHR indicates that in this animal model of hypertension the function of ACE is genetically altered in the cerebral microvessels, which may be correlated with the alteration of the cerebral microcirculation and pathogenesis of hypertension.     

Early Chronotype and Tissue-Specific Alterations of Circadian Clock Function in Spontaneously Hypertensive Rats

Malfunction of the circadian timing system may result in cardiovascular and metabolic diseases, and conversely, these diseases can impair the circadian system. The aim of this study was to reveal whether the functional state of the circadian system of spontaneously hypertensive rats (SHR) differs from that of control Wistar rat. This study is the first to analyze the function of the circadian system of SHR in its complexity, i.e., of the central clock in the suprachiasmatic nuclei (SCN) as well as of the peripheral clocks. The functional properties of the SCN clock were estimated by behavioral output rhythm in locomotor activity and daily profiles of clock gene expression in the SCN determined by in situ hybridization. The function of the peripheral clocks was assessed by daily profiles of clock gene expression in the liver and colon by RT-PCR and in vitro using real time recording of Bmal1-dLuc reporter. The potential impact of the SHR phenotype on circadian control of the metabolic pathways was estimated by daily profiles of metabolism-relevant gene expression in the liver and colon. The results revealed that SHR exhibited an early chronotype, because the central SCN clock was phase advanced relative to light/dark cycle and the SCN driven output rhythm ran faster compared to Wistar rats. Moreover, the output rhythm was dampened. The SHR peripheral clock reacted to the dampened SCN output with tissue-specific consequences. In the colon of SHR the clock function was severely altered, whereas the differences are only marginal in the liver. These changes may likely result in a mutual desynchrony of circadian oscillators within the circadian system of SHR, thereby potentially contributing to metabolic pathology of the strain. The SHR may thus serve as a valuable model of human circadian disorders originating in poor synchrony of the circadian system with external light/dark regime.     

Catecholamine Content Changes in Brain Regions of Spontaneously Hypertensive Rats Under Immobilization Stress

We compared the effect of immobilization stress on noradrenaline (NA) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) content in two brain regions--diencephalon and pons-medulla oblongata--in young and adult spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). In SHR, NA content decreased with time after the onset of the stress, whereas levels of its metabolite MHPG increased. In WKY, NA and MHPG showed no change. The MHPG/NA ratio in both regions increased relative to the duration of the stress in SHR, whereas it remained almost constant in WKY. The rate of increase in the ratio was much higher in the diencephalon of adult (12-week-old) than of young (4-week-old) SHR. In SHR, NA turnover in the brain is readily affected by environmental stress, and these changes in the noradrenergic system may induce or sustain hypertension.     

卡托普利单次和多次给药对自发性高血压大鼠模型的作用

目的探讨自发性高血压大鼠（SHR）是否同时适用抗高血压药物单次给药的快速评价和连续给药的降压效果评价。方法SHR大鼠分组给药后,用Powlab/16sp测量单次和多次给药后不同时间点SHR大鼠SAP、DAP、BMP和HR的变化。结果卡托普利单次给药1~2 h内对收缩压和舒张压有明显的降压作用（P〈0.05）,而连续给药随着给药时间延长给药28 d降压作用更为明显（P〈0.01）。结论自发性高血压大鼠既可用于降压药连续给药的药效学评价,也适用于单次给药的降压药快速筛选。     

不同年龄自发性高血压大鼠心脏AT2R的表达与心肌纤维化

目的观察不同年龄自发性高血压大鼠（SHR）心脏AT2R的表达水平及心肌胶原含量,探讨AT2R在高血压发生、发展过程中的作用。方法 1月龄组（S1）、2月龄组（S2）、3月龄组（S3）、6月龄组（S6）和9月龄组（S9）雄性SHR共五组,每组各6只,各组均有相应月龄的Wistar-Kyoto大鼠（WKY）作对照。采用RBP-I型大鼠血压心率测定仪测量大鼠动脉收缩压（SBP）;放免法（RIA）测定血浆血管紧张素Ⅱ（AngⅡ）;免疫组化染色结合计算机图像分析方法测定心脏AT2R的表达水平,天狼星红胶原染色大鼠的心脏切片。结果 1.SHR SBP随着月龄的增加呈持续上升（P〈0.05）,SHR的SBP均高于相应配对的WKY组（P〈0.05）。2.一个月后SHR血浆AngⅡ浓度均高于S1（P〈0.05）,一个月后SHR血浆AngⅡ浓度均高于相应配对的WKY组（P〈0.05）。3.SHR心脏AT2R免疫染色阳性面积比随着月份的增加而降低,SHR心脏AT2R免疫染色阳性面积比均低于相应配对的WKY组（P﹤0.05）4.SHR心肌中的胶原含量随着月龄的增加而增加。结论 SHR心脏AT2R表达水平比WKY低,并随着年龄的增加而降低。SHR心肌中的胶原含量随着月龄的增加而增加,而WKY无类似趋势。     

The Effects of Physical Exercise on the Serum Iron Profile in Spontaneously Hypertensive Rats

The purpose of this study was to evaluate the profile of serum iron in spontaneously hypertensive rats after an aerobic physical exercise. To accomplish this, 12 normotensive Wistar rats and 12 spontaneously hypertensive rats were distributed into “physical exercise” and “no physical exercise” groups. The animals in the physical exercise group underwent to an aerobic exercise for a total of 4 weeks. Blood was collected for the analysis of iron. Our results indicate that rats of the physical exercise group had significantly lower serum iron levels after the aerobic exercise protocol compared to the spontaneously hypertensive rats no physical exercise group (F _(3,16) = 4.4915, p < 0.01). No significant difference was found between no physical exercise groups. The results indicated that the difference in iron may be due to an increased demand for iron, prompted by chronic physical exercise. In addition, erythrocytosis has been associated with increased blood pressure in spontaneously hypertensive rats, suggesting that iron reduction may be related to decreased blood pressure in these animals.