Phenotypic selection: a successful strategy to fix major genes of hypertension.

Hypertension is dominantly inherited in cross hybrids between hypertensive SHR/Mol and normotensive BB/OK rats. We used these cross hybrids for repeated backcrossing of selected hypertensive animals onto normotensive BB/OK rats to fix high blood pressure and to generate a hypertensive and diabetic BB/OK rat subline. After 8 backcrosses, the backcross parents were genetically analysed with the aid of 259 microsatellite markers to identify SHR genes causing blood pressure of 177 +/- 10 mmHg in this BB/OK rat subline. Loci on chromosomes 1, 14 and 18 showed longest heterozygosity. These loci might contain major genes of the SHR rat causing hypertension in this BB/OK rat subline. This classical strategy seems to be most suitable to fix major genes of hypertension in particular and complex traits in general and therefore to generate new animal models.     

Neonatal intermittent hypoxia and hypertension

Obstructive apnea during sleep is accompanied by intermittent hypoxia (IH) leading to hypertension and other cardiovascular disturbances. A comparative evaluation of long-term effects of the neonatal IH on the cardiovascular functions was performed in normotensive Sprague-Dawley and spontaneously hypertensive rats (SHR). The newborn rats were placed for 30 days to conditions of IH (8% and 21% O₂, alternating every 90 s for 12 h/day). Control groups of rats were constantly kept in normoxia. By 6 months, in the spontaneously hypertensive rats exposed to IH at the period of wakefulness there was a statistically significant increase (as compared with control) of the systolic (185.8 ± 1.7 and 169.9 ± 1.4 mm Hg, correspondingly, p < 0.010 and the diastolic pressure (96.2 ± 4.9 and 86.0 ± 2.6 mm Hg, correspondingly, p < 0.01). During sleep, the systolic and diastolic pressure in these rats was higher than in control animals by 10 mm Hg (p < 0.01) and 12 mm Hg (p < 0.01), its decrease during sleep being absent. In SHR submitted to IH there was an increase in the power ratio of the heart rate variability from 0.9 ± 0.15 to 1.5 ± 0.17, which indicates a shift of the sympathico-parasympathetic balance in this group towards predominance of the sympathetic component. In the Sprague-Dawley rats exposed to neonatal hypoxia, the above-indicated changes were not prominent. These peculiarities of the hypertensive rats allow establishing connection of the genetic factor with the sympathetic mechanism providing long-term consequences of the neonatal IH for the cardiovascular control in the SHR.     

红细胞抗高血压因子降压作用的进一步研究

我们曾报道原发性高血压患者(EHS)红细胞抗高血压因子(AHF)具有缓慢而持久的降压作用。本工作表明,AHF对卒中易感型自发性高血压大鼠(SHRsp)还具有快速短暂的降压作用,注射AHF后10—30s,SHRsp收缩压从原水平的26.8±1.7kPa降至20.1±1.5kPa(P<0.001)。正常人和大鼠红细胞AHF的降压作用明显强于EHS和高血压大鼠AHF。此外我们还发现EHS血浆中存在升压物质。以上结果提示,AHF缺乏和升压物质含量相对较高可能是原发性高血压发病的一个重要原因。     

Antihypertensive Effect of Angiotensin I-Converting Enzyme Inhibitory Peptides from a Sesame Protein Hydrolysate in Spontaneously Hypertensive Rats

Sesame peptide powder (SPP) exhibited angiotensin I-converting enzyme (ACE) inhibitory activity, and significantly and temporarily decreased the systolic blood pressure (SBP) in spontaneously hypertensive rats (SHRs) by a single administration (1 and 10 mg/kg). Six peptide ACE inhibitors were isolated and identified from SPP. The representative peptides, Leu-Val-Tyr, Leu-Gln-Pro and Leu-Lys-Tyr, could competitively inhibit ACE activity at respective Ki values of 0.92 μM, 0.50 μM, and 0.48 μM. A reconstituted sesame peptide mixture of Leu-Ser-Ala, Leu-Gln-Pro, Leu-Lys-Tyr, Ile-Val-Tyr, Val-Ile-Tyr, Leu-Val-Tyr, and Met-Leu-Pro-Ala-Tyr according to their content ratio in SPP showed a strong antihypertensive effect on SHR at doses of 3.63 and 36.3 μg/kg, which accounted for more than 70% of the corresponding dosage for the SPP-induced hypotensive effect. Repeated oral administration of SPP also lowered both SBP and the aortic ACE activity in SHR. These results demonstrate that SPP would be a beneficial ingredient for preventing and providing therapy against hypertension and its related diseases.     

慢性缺氧对自发性高血压大鼠血液动力学和血管反应性的影响

本研究观察了鼠龄10周的自发性高血压大鼠(SHR)在慢性缺氧条件下(模拟海拔5000m,15d)体动脉压(SBP)、平均肺动脉压(MPAP)、左、右心室收缩指数(LVIC、RVIC)和舒张指数(LVIR、RVIR)以及血管反应性的变化。结果表明,慢性缺氧明显阻抑SHR大鼠SBP升高(P<0.05),但使SHR大鼠MPAP升高(P<0.001)。慢性缺氧还可增大SHR大鼠LVIC和LVIR,增强SHR大鼠胸主动脉对乙酰胆碱(ACh)的舒张反应,减弱其对5-羟色胺(5-HT)的收缩反应。SHR大鼠肺动脉对ACh和5-HT的反应则与主动脉相反。实验结果提示,慢性缺氧阻抑SHR大鼠血压升高与血管反应性的改变有关。     

Cerebral Blood Flow Threshold and Regional Heterogeneity of Heat Shock Protein 72 Induction Following Transient Forebrain Ischemia in Rats

Heat shock proteins (HSPs) induced by brain ischemia may play an important role in neuroprotection from neuronal degeneration. In this study, we examined the cerebral blood flow (CBF) threshold to produce regional differences in HSP72 induction after transient forebrain ischemia in spontaneously hypertensive rats (SHRs). Female SHRs were subjected to 20 min of cerebral ischemia induced by bilateral carotid artery occlusion. The CBF was measured by laser Doppler flowmetry. At forty-eight hours after cerebral ischemia and reperfusion, the rats were decapitated and the brains were removed. Specific areas (hippocampal CA1, CA2-3, dentate gyrus, dorsolateral and ventromedial striatum, and parietal cortex) were thereafter dissected from the brain. The amounts of HSP72 in these samples were determined using Western blot analysis. In the hippocampus, HSP72 was induced when the CBF decreased to less than 18–25% of the resting level. The mean values of HSP72 produced in the CA1 area, CA2-3 area, and the dentate gyrus following ischemia and reperfusion treatment were 4.44 ± 1.43 (±SD) ng/g prtein, 3.51 ± 0.72 ng/g protein and 3.77 ± 1.05 ng/g protein, respectively. In the parietal cortex, the amount of HSP72 induction was less pronounced (2.55 ± 0.40 ng/g protein), while HSP72 was hardly detected at all in the striatum, even under conditions of very severe CBF reduction and reperfusion. We demonstrated the existence of both a CBF threshold (i.e., approximately 20% of the resting level) for HSP72 induction and regional heterogeneity for the induction of HSP72 protein.     

Comparisons of Characteristics of Mercury-Tolerant Bacterium Pseudomonas oleovorans G-1 and Its Mercury-Sensitive Mutant Strain

An Hg²⁺-sensitive mutant strain was isolated from an Hg²⁺-tolerant bacterium Pseudomonas oleovorans G-1 strain by mutagenesis with N-methyl-N′-nitro-N-nitrosoguanidine. The Hg²⁺-sensitive mutant strain was about 10-times as sensitive to Hg²⁺ as the parent strain. Moreover, the mutant strain was considerably more sensitive to Cr⁶⁺ than the parent strain, but it did not show an appreciable change in sensitivity to Cd²⁺ and Cu²⁺. The mutant strain was considerably more sensitive to antibiotics achromycin, chloramphenicol and streptomycin than the parent strain. A more rigid structure was observed in the cell envelope of the mutant strain than the parent strain under transmission electron microscope. Higher amounts of DNA but less protein and RNA were found in the mutant strain compared to the parent strain. Disc electrophoretic patterns showed some differences in protein bands between the parent and mutant strain.     

心钠素表达细胞移植降低高血压大鼠的血压和增加其尿量

为探讨心钠素基因转移治疗高血压和慢性心肾功能衰竭等慢性疾病的潜力,首先利用逆转录病毒载体获得可表达和分泌人心钠素的遗传工程细胞,然后将这种细胞植于自发性高血压大鼠SHR的皮下。结果发现,人心钠素遗传工程细胞的移植可使动物血浆中的心钠素浓度在移植后第7天时明显升高。在整个实验期间,虽然实验组动物的血压会随个体发育而逐渐升高,但在实验开始后的42 d内却始终明显低于空载体组,其中第14天血压的差异高达33 mm Hg。在实验开始后的第14天和第21天,实验组动物的尿量也明显增加。以上结果说明,人心钠素遗传工程细胞的皮下移植可明显抑制SHR大鼠血压的上升趋势和改善其泌尿功能,提示该方法具有治疗高血压和慢性心肾功能衰竭等慢性疾病的潜力。     

Nutritional Prevention on Hypertension, Cerebral Hemodynamics and Thrombosis in Stroke-Prone Spontaneously Hypertensive Rats

1. Stroke-prone spontaneously hypertensive rats (SHRSP/Izm), which become severely hypertensive and exhibit a very high incidence of stroke (cerebral hemorrhage and/or infarction), are used widely for the study of the hypertension and stroke. In the previous study, we indicated that high thrombotic tendency of cerebral microvessels in SHRSP/Izm compared with stroke-resistant SHR (SHR/Izm) and normotensive Wistar Kyoto rats (WKY/Izm) at aged period. 2. L-arginine, a substrate of nitric oxide (NO), and voluntary exercise reduced blood pressure and thrombotic tendency in cerebral microvessels caused by highly production of NO in vivo. Furthermore, antioxidants show that the effects of antihypertensive and antithrombosis in SHRSP/Izm. 3. Although SHRSP/Izm become genetically hypertensive and exhibit stroke, a number of nutritional factors, particularly antioxydative nutrient, have preventive effects on hypertension, cerebral blood flow dysfunction, thrombus formation, and neuronal cell death in SHRSP/Izm. Our results indicate that those treatments are beneficial in the prevention of hypertension and stroke and that the nutritional science is very important for "prediction and prevention medicine."     

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.     

正常大鼠植入高血压大鼠肾脏后动脉血压的变化

本实验对12周龄的自发性高血压大鼠(spontaneouslyhypertensiverat,SHR)及其对照组WistarKyoto(WKY)大鼠进行了肾脏移植的研究,并观察受肾移植大鼠动脉血压的变化以及免疫抑制剂对动脉血压的影响。用尾套法对接受同窝另一同胞WKY大鼠肾脏移植且存活5周的6只WKY大鼠(A组)及接受SHR肾脏移植且存活5周的6只WKY大鼠(B组)的尾动脉收缩压进行检测,移植前A、B两组受肾移植大鼠的尾动脉收缩压分别为180±093和183±068kPa,无统计学显著差异(P>005);移植后3、4、5周时,B组大鼠的尾动脉收缩压显著高于A组大鼠,移植后5周时,A,B两组大鼠的收缩压分别为190±071和230±069kPa(P<0001);所用剂量的免疫抑制剂CsA对双侧肾脏完整以及右侧肾脏切除的SHR、WKY大鼠的动脉血压无显著影响。以上结果表明,SHR的肾脏在高血压的形成中可能起重要作用     

替米沙坦及吡哆胺对自发性高血压大鼠脑组织氧化应激的影响

目的:探讨替米沙坦及吡哆胺对自发性高血压大鼠脑组织氧化应激的影响。方法:自发性高血压大鼠24只随机分为4组(n=6):高血压对照组(HC组);替米沙坦组(T组);吡哆胺组(P组);联合治疗组(TP组)。同龄WKY大鼠作为正常对照组(NC组)。药物干预16周,测定各组脑组织中丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性及烟酰胺腺嘌呤二核苷酸磷酸(NADPH)氧化酶p47phox mRNA表达。结果:与NC组比较,HC组脑组织中MDA含量明显升高、SOD活性明显减低(P<0.05);与HC组比较T组、P组、TP组MDA含量明显减低,SOD活性明显升高(P<0.05);与NC组比较HC组(NADPH)氧化酶p47phox mRNA表达显著上调(P<0.01);与HC组比较T组、TP组NADPH氧化酶p47phox mRNA表达明显下调(P<0.01);HC组与P组比较NADPH氧化酶p47phox mRNA表达无统计学差异(P>0.05)。结论:自发性高血压大鼠脑组织处于氧化应激状态,替米沙坦及吡哆胺可抑制自发性高血压大鼠脑组织的氧化应激水平,联合治疗并不优于替米沙坦单药治疗。     

Protein kinase C isozymes in hypertension and hypertrophy: Insight from SHHF rat hearts

Chronic hypertension results in cardiac hypertrophy and may lead to congestive heart failure. The protein kinase C (PKC) family has been identified as a signaling component promoting cardiac hypertrophy. We hypothesized that PKC activation may play a role mediating hypertrophy in the spontaneously hypertensive heart failure (SHHF) rat heart. Six-month-old SHHF and normotensive control Wistar Furth (WF) rats were used. Hypertension and cardiac hypertrophy were confirmed in SHHF rats. PKC expression and activation were analyzed by Western blots using isozyme-specific antibodies. Compared to WF, untreated SHHF rats had increased phospho-active (10-fold), (4-fold), and (3-fold) isozyme expression. Furthermore, we analyzed the effect of an angiotensin II type 1 receptor blocker (ARB) and hydralazine (Hy) on PKC regulation in SHHF rat left ventricle (LV). Both the ARB and Hy normalized LV blood pressure, but only the ARB reduced heart mass. Neither treatment affected PKC expression or activity. Our data show differential activation of PKC in the hypertensive, hypertrophic SHHF rat heart. Regression of hypertrophy elicited by an ARB in this model occurred independently of changes in the expression and activity of the PKC isoforms examined. (Mol Cell Biochem 270: 63–69, 2005)     

Conjugated linoleic acid prevents the development of essential hypertension in spontaneously hypertensive rats

Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of linoleic acid found in beef, lamb, and dairy products. CLA has attracted considerable attention over the past several decades because of its potentially beneficial biologic effects, including protective effects against several cancers, atherosclerosis, and obesity. In previous studies, we provided evidence that dietary CLA could prevent the development of obesity-related hypertension in obese animals. Here, we show that CLA suppresses the development of non-obese essential hypertension in spontaneously hypertensive rats (SHRs). After 4 weeks of feeding with CLA, the increase of systolic blood pressure was significantly suppressed compared with rats fed linoleic acid. Abdominal adipose tissue weight was also significantly lowered in CLA-fed SHRs. Content of arachidonic acid, the substrate of eicosanoid production, was not changed, but accumulation of oleic acid, the lipogenesis end-product, was markedly decreased in the membrane phospholipids of CLA-fed SHRs. In addition, we found increased level of plasma adiponectin, suggested as a regulatory factor of hypertension, through the enhancement of mRNA expression in CLA-fed SHRs. We speculate that the antihypertensive effect of dietary CLA may be due to the increase of plasma adiponectin level and associated with the alleviation of membrane abnormality in SHRs.     

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.     

SHR与WKY大鼠肾脏组织基因表达差异分析

为了观察SHR与WKY大鼠肾脏组织的基因表达的差异,用T11G、AP6引物对12周龄的SHR与WKY大鼠肾脏mRNA进行了差异显示,得到了一条在SHR大鼠肾脏组织中高表达的差异显示条带,进一步分析证明这一差异显示条带含有170 bp,与GenBank 收录的已知的核苷酸序列的同源性低于80%,可能为未知基因的cDNA片段,并定位于SHR大鼠的肾小管上皮细胞内.     

Diverse development and higher sensitivity of the circadian clocks to changes in maternal-feeding regime in a rat model of cardio-metabolic disease

Spontaneously hypertensive rats (SHR) develop cardiovascular and metabolic pathology in adulthood when their circadian system exhibits significant aberrances compared with healthy control rats. This study was aimed to elucidate how the SHR circadian system develops during ontogenesis and to assess its sensitivity to changes in maternal-feeding regime. Analysis of ontogenesis of clock gene expression rhythms in the suprachiasmatic nuclei, liver and colon revealed significant differences in SHR compared with Wistar rats. In the suprachiasmatic nuclei of the hypothalamus (SCN) and liver, the development of a high-amplitude expression rhythm selectively for Bmal1 was delayed compared with Wistar rat. The atypical development of the SHR circadian clocks during postnatal ontogenesis might arise from differences in maternal behavior between SHR and Wistar rats that were detected soon after delivery. It may also arise from higher sensitivity of the circadian clocks in the SHR SCN, liver and colon to maternal behavior related to changes in the feeding regime because in contrast to Wistar rat, the SHR SCN and peripheral clocks during the prenatal period and the hepatic clock during the early postnatal period were phase shifted due to exposure of mothers to a restricted feeding regime. The maternal restricted feeding regime shifted the clocks despite the fact that the mothers were maintained under the light/dark cycle. Our findings of the diverse development and higher sensitivity of the developing circadian system of SHR to maternal cues might result from previously demonstrated differences in the SHR circadian genotype and may potentially contribute to cardiovascular and metabolic diseases, which the animal model spontaneously develops.     

自发性高血压大鼠多组织炎症状态

高血压是一种慢性血管性疾病,易累及肾、肝、心、脑等组织,引起脑卒中和心、肾损害等并发症.本研究对高血压时肾、肝、心、脑等组织的炎症状态进行了观察.实验采用自发性高血压大鼠(spontaneously hypertensive rat,SHR)和正常血压的Wistar-Kyoto(WKY)大鼠,用RT-PCR和Western blot法观察肾、肝、心、脑等组织炎症相关因子IL-1p、TNFα、ICAM-1、iNOS、C/EBPδ和PPARγ的基因表达;紫外分光光度法观察蛋白质羰基化水平和FRAP法检测组织总抗氧化能力.结果显示(1)SHR组织炎症相关因子表达较对照WKY增强,除IL-1βmRNA在肝和脑的增加不明显外,其余均有显著性差异(P＜0.05);(2)SHR和WKY大鼠肾、心、脑蛋白质羰基化水平(nmol/mg蛋白)分别为8.93±1.08和2.27±0.43、2.23±0.23和0.17±0.02、13.42±1.10和5.72±1.01,SHR明显增加(P＜0.05);而肝脏蛋白质羰基化水平无明显变化;(3)SHR肾、肝、心、脑总抗氧化能力水平显著低于WKY大鼠(P＜0.05).以上结果表明,SHR多个组织(肾、肝、心和脑)均存在炎症因子被诱导和氧化应激反应等明显的炎症状态,提示炎症可能在高血压及其并发症的病理改变中起重要作用.     

Improvement of hypertension and vascular dysfunction by hydroxyhydroquinone-free coffee in a genetic model of hypertension

Chlorogenic acid, a polyphenol found in coffee, has antihypertensive actions, but epidemiologic data on the effects of coffee on blood pressure are controversial. Specific coffee components that inhibit the hypotensive effect of chlorogenic acid and the physiologic mechanisms underlying the effects of coffee without these components were investigated. One component, hydroxyhydroquinone (HHQ), inhibited the hypotensive effects of chlorogenic acid in spontaneously hypertensive rats (SHR). The attenuation of hypertension by HHQ-free coffee was associated with nitric oxide, the suppression of mRNA expression of NAD(P)H oxidase, and the improvement in endothelium-dependent vasodilation in the aorta. Thus, HHQ-free coffee might regulate vascular tone by improving the bioavailability of nitric oxide in SHR.