Circulating and local visfatin/Nampt/PBEF levels in spontaneously hypertensive rats,stroke-prone spontaneously hypertensive rats and Wistar-Kyoto rats

Visfatin (also known as nicotinamide phosphoribosyltransferase and pre-B cell colony-enhancing factor) is a multifunctional protein. Visfatin has been reported to be involved in several biological processes in the cardiovascular system, . However, the role of visfatin in hypertension is still unclear. In this study, we examined the circulating and local adipose visfatin levels in spontaneously hypertensive rats (SHR), stroke-prone spontaneously hypertensive rats (SHR-SP), and in their normotensive control Wistar-Kyoto (WKY). SHR and SHR-SP rats exhibited lower body weight, lower fat tissue and hypolipidemia. No differences of serum visfatin levels were observed in SHR/SHR-SP and WKY. Serum visfatin levels did not correlate to serum glucose, lipids, insulin, and fat pad weights, but significantly correlated to weights of skeletal muscle. Visfatin expression in visceral fat tissue was slightly lower in SHR-SP compared with that in WKY. Moreover, there were no significant differences of visfatin expression in skeletal muscles among WKY, SHR and SHR-SP. Finally, visfatin protein was detected in L6 rat skeletal muscle cell culture medium, indicating that visfatin was secreted from skeletal muscle cells. Thus, our results may provide useful information for understanding the characteristic of visfatin in hypertensive models, and support the view that visfatin may be a myokine.     

WKY大鼠与自发性高血压模型大鼠(SHR)大脑中动脉拉伸力学特性的对比分析

对比分析WKY大鼠和SHR大鼠大脑中动脉的拉伸力学特性,为预防高血压提供生物力学基础。取5月龄正常WKY雄性大鼠大脑中动脉20个,5月龄SHR雄性大鼠大脑中动脉20个,试样以0.5mm/Min的实验速度进行纵向拉伸实验。WKY雄性大鼠大脑中动脉组拉伸最大应力、最大应变、弹性限度应变大于SHR雄性大鼠大脑中动脉组(P0.05),SHR雄性大鼠大脑中动脉的弹性模量值大于WKY雄性大鼠大脑中动脉(P0.05)。WKY大鼠大脑中动脉和自发性高血压模型大鼠(SHR)大脑中动脉具有不同的拉伸力学特性,自发性高血压模型大鼠(SHR)大脑中动脉拉伸力学特性发生了改变。     

An increase in the sympathoadrenal medullary function in stroke-prone spontaneously hypertensive rats under anesthetized and resting conditions

Sympathoadrenal medullary functions were investigated in stroke-prone spontaneously hypertensive rats (SHR-SP) and in control normotensive Wistar-Kyoto rats (WKY) under halothane-anesthetized and resting conditions. The mean frequency of the spontaneous efferent activity of a single adrenal sympathetic nerve fiber was 1.08 +/- 0.11 impulses/s in WKY and 2.82 +/- 0.24 imp/s in SHR-SP, indicating a much higher level in SHR-SP than in WKY. The secretion rates of both adrenaline and noradrenaline from the adrenal gland were higher in SHR-SP than in WKY. The secretion rates of adrenaline and noradrenaline in WKY were 16.8 +/- 3.0 and 1.70 +/- 0.09 ng/kg X min, respectively, while those in SHR-SP were 36.7 +/- 3.9 and 2.56 +/- 0.18 ng/kg X min, respectively.     

Patterns of behavioral development in spontaneously hypertensive rats and Wistar-Kyoto normotensive controls

We have examined the behavior of spontaneously hypertensive (SHR) rats and stroke-prone hypertensive (SP-SHR) male rats during the development and maintenance of elevated blood pressure and compared this pattern with age- and gender-matched normotensive (WKY) rats of the same Wistar-Kyoto strain as controls. Rats of each strain (n = 10/age group) were isolated in individual cages and observed for 60 min at 3,4,6,8,10, or 20 weeks of age using a scan sampling technique. At all ages SHR rats were significantly more active than WKY rats whereas SP-SHR rats were intermediate in level of activity. In a 2nd series, activity of male rats of each strain was monitored continuously for 24 hr in the home cage. No strain differences in amount or pattern of total daily activity were evident at either 4-6 or 16-18 weeks of age. These results indicate that SHR rats are more reactive to environmental change, but the intermediate level of activity of SP-SPHR rats suggests that this response is not related to the degree of blood pressure elevation,     

Enhanced oxidative stress and impaired thioredoxin expression in spontaneously hypertensive rats

As oxidative stress plays a crucial role in the development and pathogenesis of hypertension, we analyzed the redox (reduction/oxidation) status in tissues from Wistar-Kyoto rats (WKY), spontaneously hypertensive rats (SHR), and stroke-prone SHR (SHRSP). Expressions of 8-hydroxy-2'-deoxyguanosine, a marker for oxidative stress-induced DNA damage, and protein carbonylation, a marker for oxidation status of proteins, were enhanced in aorta, heart, and kidney from SHR and SHRSP compared with WKY. The expression of redox regulating protein, thioredoxin (TRX), estimated by immunohistochemistry and western blot, and expression of TRX gene estimated by real-time RT-PCR were markedly suppressed in those tissues from SHR and SHRSP compared with WKY. Induction of TRX was impaired after angiotension II treatment in peripheral blood mononuclear cells isolated from SHR and SHRSP compared with those isolated from WKY. Although previous reports have shown that TRX is induced by a variety of oxidative stress in tissues, the present study shows the impaired induction of TRX in tissues from genetically hypertensive rats despite the relative increment of oxidative stress. Redox imbalance in essential organs may play a crucial role in the development and pathogenesis of hypertension.     

On the Activation of Calcium-Dependent Proteolysis in Brain Neurons of Spontaneously Hypertensive Rats (SHR Strain)

Females of spontaneously hypertensive (SHR strain) and normotensive rats (WKY strain and Wistar) received drinking water with normal (80 mg/liter) or reduced concentration of Ca²⁺ (8 mg/liter). Activity of calcium-dependent calpain protease in neurons did not differ in 18-dayold rat pups born and suckled by these animals. Our results are consistent with published data on normal metabolism of SHR rats up to the age of 30 days.     

Differences between natriuretic peptide receptors in the olfactory bulb and hypothalamus from spontaneously hypertensive and normotensive rat brain

Natriuretic peptide receptor-A (NPR-A) functional characteristics in the hypothalamus and olfactory bulb (OB) have been investigated in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Autoradiographic studies demonstrate a decreased number of atrial natriuretic peptide (ANP) binding sites in the olfactory bulb and hypothalamus in SHR compared to WKY rats. We found that NPR-A showed a lower maximal binding capacity (B(max)) and higher affinity in SHR than in WKY rats both in the olfactory bulb and hypothalamus. However, despite the lower B(max) in SHR, both ANP(1-28) and ANP(5-25) stimulated similar or greater cGMP production than in WKY rats. These differences were found even before the development of hypertension. NPR-A in the olfactory bulb and hypothalamus from 3-week-old SHR showed a lower B(max) and K(d) and a higher cGMP production rate than in WKY rats, suggesting that these characteristics are intrinsic of NPR-A in SHR, instead of being a result of hypertension itself. The present study provides evidences for altered NPR-A receptor properties and function in the olfactory bulb and hypothalamus from SHR, which might be involved in the pathogenesis of hypertension.     

Cerebrovascular permeability in stroke-prone spontaneously hypertensive rats

Cerebrovascular permeability in the stroke-prone strain of spontaneously hypertensive (SHR) rats drinking a 1% NaCl solution was examined by injection of Evan's blue, or ¹²⁵I-labeled human serum albumin (¹²⁵I-HSA), before and immediately after the onset of stroke. Leakage of Evan's blue was locally found in the brain or spinal cord from rats with stroke signs, but not in those from rats without the signs. Examination of serial sections of the blue areas revealed association of dye leakage with pathological changes such as medial thickening and fibrinoid degeneration of arterioles, petechial hemorrhage, and edema. The increased cerebrovascular permeability to ¹²⁵I-HSA was observed only in the blue spot areas but not in other parts of brain even in the rats with stroke signs. These findings indicate that increased cerebrovascular permeability is limited to the focal area with small vascular lesions which are closely related to the onset of stroke.     

No aggravation of the course of experimental glomerulonephritis in spontaneously hypertensive rats.

Functional and morphologic glomerular alterations induced by antiglomerular basement membrane (anti-GBM) nephritis were investigated in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto controls (WKY) for assessment of the role of systemic hypertension in immunologically mediated renal injury. Over a 6-week period serial measurements of systolic blood pressure (BP), serum creatinine (SCreat), creatinine clearance (CCreat), and urinary albumin excretion (UAlbV) were obtained with inulin clearances (CInulin) at the end of the study. Renal tissue was examined by light microscopy (LM), electron microscopy, immunofluorescence, flash 3H-thymidine autoradiography (AR), and staining for nonspecific esterase (NSE). Immunologic humoral response was evaluated by measurement of rat anti-rabbit IgG antibody production. At all time periods studied, SHR and WKY rats with anti-GBM nephritis demonstrated comparable elevations in SCreat and UAlb V as well as diminution of CCreat and CInulin as compared with non-nephritic control rats of each strain. In nephritic WKY rats mild hypertension developed, whereas in nephritic and control SHR rats marked elevations in BP developed. Morphologic injury as assessed by percent glomerular crescents and hypercellularity on LM, numbers of monocyte macrophages by NSE staining, immunofluorescence for IgG, C3, fibrinogen and Ia positivity, and numbers of glomerular 3H-thymidine-labeled cells by AR was notably comparable in both nephritic strains. Humoral antibody responses were also shown to be similar in all rats studied. These results demonstrate that the 5-week course of experimental anti-GBM nephritis is not exacerbated by systemic hypertension. Glomerular autoregulatory capacity may be important in determining the extent of immune-mediated renal injury.     

Tissue and blood magnesium levels in spontaneously hypertensive rats, at rest and in stressful conditions

Magnesium (Mg) levels were measured by flame atomic absorption spectrophotometry in the blood (plasma, erythrocytes) and soft tissues (liver, brain, heart, aorta, kidneys, adrenals, spleen, thymus) of adult spontaneously hypertensive rats (SHR) and their normotensive controls, Wistar Kyoto (WKY). In experiment 1, Mg determinations were performed on eight animals of each strain at rest. Mg levels were lower in brain (P less than or equal to 0.05), kidneys (P less than or equal to 2.10(-4] and erythrocytes P less than or equal to 0.01) in SHR than in WKY rats. Tissue water content was the same in the two strains. These results suggest the occurrence of lower intracellular Mg levels in SHR than in WKY. In experiment 2, 15 SHR and 15 WKY were submitted either to acute (1 d) or subacute (22 d) stresses or reared in restful conditions. Acute stress induced important Mg shifts leading to a decreased difference between SHR and WKY in most tissues and to an increased and more significant difference (P less than or equal to 0.01) in spleen and plasma Mg levels. Subacute stress was milder and had little effect. It is concluded that the results of experiment 1 cannot be attributed to the greater sensitivity of SHR to laboratory manipulations. When compared with previously published data our results nevertheless suggest an association between stress sensitivity and genetic factors regulating Mg metabolism.     

Effects of ageing on cardiac performance and coronary flow in spontaneously hypertensive and normotensive rats

The aim of the present study was to assess the influence of ageing on cardiac function and coronary flow in Wistar Kyoto normotensive rats (WKY, 16 and 78 weeks of age) and spontaneously hypertensive rats (SHR) of the same age. Cardiac function was determined on isolated hearts by means of an antegrade heart perfusion technique. Left atrial pressure and peak aortic pressure could be altered independently of each other. Recordings of cardiac output and coronary flow were then obtained at both normotensive and hypertensive levels of peak aortic pressures. Peak stroke volume (SV) was reduced with age in both WKY and SHR. Peak SV determined at normotensive pressure loads became diminished with age in WKY, while it at hypertensive pressure loads showed a small decline with age, since peak SV was low as early as 16 weeks of age. The age-dependent fall in cardiac performance was greater in SHR than in WKY, due to the enhanced peak SV in 16-week-old SHR at hypertensive pressure loads. Peak SV was markedly decreased at normotensive pressure levels in both 16- and 78-week-old SHR v. age-matched WKY. Coronary flow per unit tissue declined with age both in WKY and SHR. Coronary flow was also lower in SHR compared to age-matched WKY. With ageing this elevated performance was reduced down to the same level as in 78-week-old WKY. The age-related coronary flow reduction and the consistently reduced flow in SHR indicate a structural narrowing of the coronary vascular bed, particularly in SHR.     

自发性高血压鼠心肌内去甲肾上腺素的变化

运用高效液相色谱电化学检测仪测定24只自发性高血压鼠(SHR)心肌内去甲肾上腺素(NA)的含量。SHR分成3个月与6个月龄两组,并与同龄组的正常血压京都种大白鼠(WKY)作比较。结果在3个月龄组的SHR心肌内NA含量低于WKY,而6个月龄组的SHR则高于WKY,两者都有显著性差异。同时亦测量了它们的血压变化。     

基质金属蛋白酶及其组织型抑制剂活性及表达失衡与高血压性左心室重塑的关系

目的： 探讨慢性压力负荷增高时，大鼠左心室（LV）基质金属蛋白酶（MMPs）/组织型基质金属蛋白酶抑制剂（TIMPs）失衡与LV重塑的关系。方法：40只6周龄雄性卒中易感性自发性高血压大鼠（SHR-SPs）作为研究对象，10只同周龄雄性Wistar-Kyoto（WKY）大鼠作为对照。6个月后，以Millar压力容积导管评价2组大鼠的在体LV血流动力学，并对2组大鼠的心脏进行组织病理学、明胶酶谱和免疫印迹法分析。结果：反映LV收缩与舒张功能的血流动力学参数在2组间有显著差异（P＜0.05）；SHR-SPs心脏胶原容积分数、血管周胶原面积/管腔面积、心肌横断面积、心室壁动脉中膜面积/管腔面积均增高（P＜0.05）；心肌MMP-2活性、蛋白含量及TIMP-1蛋白含量在SHR-SPs中明显增高（P＜0.05）。结论：慢性压力超负荷能够导致心脏细胞外基质代谢失调及MMPs/TIMPs系统失衡，继而产生心室腔扩张、LV收缩与舒张功能障碍。     

The spontaneously hypertensive rat's preference for salted foods

Sprague-Dawley rats drink mild salt (NaCl) solutions in preference to plain water. In contrast, rats of this strain are less likely to show preferences when salt is tested in food. Others have established that rats of the spontaneously hypertensive strain (SHR) have greater preferences for salt water than do their normotensive counterparts (WKY). The question addressed in the present research was whether SHR rats would show an enhanced salted food preference when compared with WKY rats. SHR and WKY rats were given choices between a variety of salted and unsalted foods. When tested with potato chips, no major strain differences in salt preferences were observed; depending on concentrations, rats ate either equal amounts of salted and unsalted chips or avoided salted chips. However, when tested with liquid milk products (heavy cream and half & half), SHR rats showed both higher salt preferences and consumed more salt. The SHR actually preferred these products salted, whereas the WKY rats, like Sprague-Dawley rats, never ate more salted milk than plain milk. When tested with skim milk, SHR and WKY did not differ; both preferred the milk salted. In order to test the effect of physical state (or texture) upon salt preference, the skim milk was gelled. Salt preferences of the SHR rats fell to 50% whereas the salt preferences of the WKY rats remained unchanged.     

Hypertensive brain damage: comparative evaluation of protective effect of treatment with dihydropyridine derivatives in spontaneously hypertensive rats

Hypertension is the main risk factor for cerebrovascular disease including vascular dementia and control of blood pressure might protect from lesions causing cognitive impairment. The influence of anti-hypertensive treatment on hypertensive brain damage was assessed in spontaneously hypertensive rats (SHR). SHR and age-matched normotensive Wistar Kyoto (WKY) rats were treated from the 14-26th week of age with the dihydropyridine-type Ca2+ channel blockers lercanidipine, manidipine and nimodipine and as a reference with the non-dihydropyridine-type vasodilator hydralazine. Volume of brain areas, number of nerve cells and glial fibrillary-acidic protein (GFAP)-immunoreactive astrocytes and neurofilament 200 kDa immunoreactivity were investigated in frontal and occipital cortex and in hippocampus. In control SHR, systolic blood pressure (SBP) was significantly higher in comparison with WKY rats. Compounds tested decreased to a similar extent SBP values in SHR, with the exception of nimodipine that caused a smaller reduction of SBP compared with other compounds. Decreased volume and number of nerve cells and loss of neurofilament protein immunoreactivity were observed in SHR. GFAP-immunoreactive astrocytes increased in number (hyperplasia) and in size (hypertrophy) in the frontal and occipital cortex of control SHR, and only in number in the hippocampus. Anti-hypertensive treatment countered in part microanatomical changes occurring in SHR. Drugs investigated with the exception of nimodipine exerted an equi-hypotensive effect. In spite of this the best protection was exerted by lercanidipine and, to a lesser extent, by nimodipine. Compared with nimodipine, lercanidipine induced a more effective decrease of SBP. This may represent an advantage in the treatment of hypertension with risk of brain damage.     

胰岛素对自发型高血压大鼠血管平滑肌细胞TGF β及其受体的调节作用

目的:从细胞增生、转化生长因子β₁和受体表达等方面,探讨胰岛素对自发型高血压大鼠血管平滑肌细胞(SHR VSMC)和正常血压Wista-Kyoto大鼠血管平滑肌细胞(WKY VSMC)的影响异同。方法:采用组织移植法培养SHR和WKY大鼠胸主动脉VSMC|用细胞计数仪和流式细胞仪分别检测细胞增生情况|TGF β及其受体的mRNA水平利用定量RT-PCR技术进行检测。结果:(1)胰岛素加强SHR VSMC的增生,而不影响WKY VSMC的增生。胰岛素加强SHR VSMC的增生,且呈剂量依赖方式(2)以20%小牛血清培养基培养VSMC, SHR VSMC的S期百分率为31.44%,而WKY VSMC的S期百分率仅为19.86%|以2%小牛血清培养基培养VSMC,SHR VSMC的G₀／G₁和S期百分率分别为73.23%和9.35%,加入胰岛素后,SHR VSMC的G₀／G₁降低为67.58%,S期百分率则增加到15.64%。但是,加入胰岛素前后,WKY VSMC各期百分率无明显变化|(3)RT-PCR分析结果表明,生长静止的SHR VSMC和WKY VSMC均有TGF β₁、Ⅰ型和Ⅱ型TGF β受体的表达,但SHR VSMC的TGFβ₁、Ⅰ型TGF β受体的表达量高于WKY VSMC的TGF β₁、Ⅰ型TGF β受体的表达量,胰岛素加强了WKY VSMC的TGF β₁、Ⅰ型TGF β受体的表达(P＜0.01和P＜0.05),而削弱了SHR VSMC相应分子的表达(P＜0.01和P＜0.05),胰岛素不影响二株系大鼠VSMC Ⅱ型TGF β受体的表达(P＜0.05)。结论:胰岛素对SHR VSMC和WKY VSMC的TGF β和它的受体表达具有不同的调节作用,这种异常调节作用可能和胰岛素加强SHR VSMC的增生密切相关。     

Induction of cardiac angiotensin I-converting enzyme with dietary NaCl-loading in genetically hypertensive and normotensive rats

We have recently shown that the angiotensin I converting enzyme (ACE) gene is linked to NaCl-loaded blood pressure in the stroke-prone spontaneously hypertensive rat (SHRSP), and that high-NaCl loading selectively stimulates ACE in the aorta of SHRSP but not in normotensive Wistar-Kyoto (WKY) rats. We therefore investigated the relationship between cardiac ACE and the development of hypertension and left ventricular hypertrophy in response to normal- and high-NaCl diet in these rats. ACE mRNA and ACE activity were measured in left ventricular tissue after completion of hemodynamic characterization of the animals. While SHRSP rats increased blood pressure (P<0.0001) and heart rate (P<0.005) in response to high NaCl, blood pressure remained unchanged in WKY. Similarly, relative left ventricular weight increased only in SHRSP after high NaCl (P<0.002). A significant two- to threefold increase of cardiac ACE mRNA and fourfold stimulation of ACE enzyme activity in response to high NaCl was found in both WKY and SHRSP rats (P<0.005). The induction of ACE gene expression was significantly more pronounced in SHRSP compared to WKY (P<0.02), whereas no significant strain differences in left ventricular ACE activity were found after either normal- or high-NaCl diet. Thus, arterial blood pressure and left ventricular weight remained unchanged in the WKY rats despite the activation of left ventricular ACE activity after high-NaCl exposure. These results demonstrate that left ventricular ACE activity is equally upregulated in response to high-NaCl in the normotensive and hypertensive strain, independently from the development of hypertension. We conclude that the pretranslational induction of left ventricular ACE with high-NaCl loading may be important both for the regulation of cardiac angiotensins and kinins and for local therapeutic ACE inhibition in the heart during high-salt status.Abbreviations ACE Angiotensin I-converting enzyme - Ang Angiotensin - LVH Left ventricular hypertrophy - PCR Polymerase chain reaction - SHRSP Stroke-prone spontaneously hypertensive rat - WKY Wistar-Kyoto     

Lack of effect of insulin on glucose utilization of the hypothalamus in normotensive and hypertensive rats

Hypertension is frequently associated with insulin resistance and enhanced sympathetic activity supposedly mediated by an effect of the hormone on the hypothalamus. In this study we sought to determine whether insulin modifies the functional activity of the hypothalamus and other brain areas of spontaneously hypertensive (SHR) and normotensive WKY rats. The study was carried out in control and hyperinsulinemic, normoglycemic rats. Insulin plasma levels were increased to 198 +/- 10 (WKY) or 220 +/- 10 microunits/ml (SHR). Brain functional activity was evaluated by the 2-[14C]deoxyglucose method for measuring local rates of glucose utilization. The results show that insulin has no effect on any of the brain areas examined including the hypothalamus, of both WKY and SHR rats. The two strains of rats have comparable cerebral metabolic rates also under basal conditions.