Left ventricular hypertrophy improves cardiac performance in spontaneously hypertensive rats

Cardiac function was studied in spontaneously breathing, adult spontaneously hypertensive rats (SHR) and Wistar-Kyoto normotensive rats (WKY). By rapid intravenous blood infusion, the relation between left ventricular end-diastolic pressure (LVEDP) and stroke volume (SV) was determined while the cardiac nervous control was pharmacologically blocked. Since SV is greatly influenced by the level of afterload (mean arterial pressure, MAP), SV was also determined at increased MAP (constriction of abdominal aorta) and at decreased MAP (vasodilation by hydralazine). At low LVEDP levels, a righward shift of the Frank-Starling relationship was observed in SHR. This rightward shift seems mainly to depend on the increased MAP present in SHR since it was less prominent if MAP was lowered to normotensive levels in SHR. Maximal SV during volume infusion was similar in SHR and WKY, despite a much higher MAP in SHR. When peak SV was instead compared at similar MAP levels for both (either at ‘normotensive’ or ‘hypertensive’ levels) it was always significantly greater in SHR, and was increased largely in proportion to their increased left ventricular weight. This indicates that the left ventricular hypertrophy present in SHR is, at least at this stage, a physiological adaptation of the heart to increase its performance, in order to maintain a normal SV and hence cardiac output, despite an increased arterial pressure.     

Myocyte loss in early left ventricular hypertrophy of experimental renovascular hypertension

Left ventricular hypertrophy (LVH) develops very early in experimental renovascular hypertension after clipping of one renal artery and is accompanied by a remodeling of cardiac structure which has not yet been investigated in detail. It was the aim of the present study to analyze changes in cardiomyocyte number and volume in LVH after 2 weeks of renovascular hypertension. Sprague-Dawley rats were subjected to clipping of the left renal artery (2K1C) or sham operation (sham). One group of 2K1C rats received antihypertensive treatment with dihydralazine. The experiment was terminated after 2 weeks. Hearts were investigated using stereological methods, electron microscopy, immunohistology for the proliferation marker proliferating cell nuclear antigen, the pro- and anti-apoptotic proteins Bax and Bcl-2 as well as the TUNEL technique. After 2 weeks, systolic blood pressure and relative left ventricular weight were significantly higher in untreated 2K1C animals than in sham and dihydralazine-treated 2K1C rats. Volume fraction of interstitial tissue and capillary length density were not different, whereas wall thickness of intramyocardial arteries was significantly higher in untreated 2K1C (5.12+/-0.7 micro m) than in sham (3.92+/-0.6 micro m) and in dihydralazine-treated 2K1C (3.91+/-0.7 micro m) rats. Cardiomyocyte diameter and volume were significantly higher in untreated 2K1C than in sham animals. The number of cardiomyocytes per left ventricle was significantly lower in untreated 2K1C rats (5.5+/-1.6 vs 3.9+/-6.9 x10(7)). Using immunohistochemistry, no direct evidence of apoptosis was found, but a relative higher expression of the anti-apoptotic protein bcl-2 expression was seen in untreated 2K1C than in sham animals. This may reflect a protective mechanism as a consequence of earlier occurring apoptosis. These observations document that experimental renovascular hypertension induces a rapidly developing LVH characterized by marked cardiac remodeling and substantial loss of cadiomyocytes.     

Mesp1-nonexpressing cells contribute to the ventricular cardiac conduction system.

Previous fate mapping analysis, using Cre recombinase driven by the Mesp1 locus, revealed that Mesp1 is expressed in almost all of the precursors of the cardiovascular system, including the endothelium, endocardium, myocardium, and epicardium. Mesp1-nonexpressing cells were found to be restricted to the outflow tract cushion and along the interventricular septum (IVS), which is a location that is suggestive of specialized cardiac conduction system (CCS). In our current study, we examined the identity of these IVS cells by using the pattern of beta-galactosidase activity in CCS-lacZ mice. In addition, by crossing Mesp1-Cre and floxed GFP reporter mice with CCS-lacZ mice, we have calculated that approximately 20% of the ventricular CCS within the IVS corresponds to Mesp1-nonexpressing cells. These data suggest that the ventricular CCS is of heterocellular origin. Furthermore, we indicate a possibility that a population of the cells that contribute to the ventricular CCS might be distinguished at an early stage of development.     

己酮可可碱对扩张型心肌病大鼠心室重构和心功能的影响

目的： 探讨己酮可可碱（PTX）对扩张型心肌病（DCM）大鼠心室重构和心功能的影响。方法: 制备DCM模型，随机分为PTX组（n=10）和DCM组（n=10），同时设正常对照组（n=10）。PTX组给予PTX 25 mg·kg^-1·d^-1, ip，其它2组给予生理盐水ip，共30 d。用ELISA法检测血浆中肿瘤坏死因子-α（TNF-α）、白细胞介素-6（IL-6）和IL-10的水平，Masson染色和免疫组化染色评估心肌纤维化情况，并采用彩色超声心动图评估心脏的结构和功能。结果: PTX组血浆TNF-α和IL-6的水平显著低于DCM组（P<0.01和P<0.05），但高于正常对照组（P<0.01）；而IL-10高于DCM组和正常对照组（P<0.05和P<0.01）。PTX组心肌纤维化程度较DCM组明显减轻，Ⅰ/Ⅲ型胶原比值降至正常对照组水平。PTX组左室舒张末期内径低于DCM组（P<0.05），而左室射血分数显著高于DCM组（P<0.01）。结论: PTX对DCM大鼠血浆中细胞因子的表达有明显作用，并可延缓心室重构，改进心功能。     

Development and regression of exercise-induced cardiac hypertrophy in rats.

Adult female rats were exercised by daily swimming. All the increase in heart weight induced by the exercise occurred within 14 days and averaged 30%. The half times of the increases in heart weight and total protein content were about 4.5 days, whereas that of cytochrome c, which was used as a mitochondrial marker, was 6.5 days. The total amounts of DNA and of hydroxyproline in the heart, which were used to evaluate the degree of connective tissue hyperplasia, increased only slightly (8% and 10%, respectively). Other animals were subjected to the same swimming program for 21 days. Groups of rats were killed at various time intervals after stopping exercise. Heart weight, total protein content, and total cytochrome c content decreased rapidly initially, with 60% of the total regression of hypertrophy occurring during the first week. Thereafter, heart weight fell more gradually toward the sedentary control value. The hydroxyproline content of the heart, which was increased 10%, did not decrease during the regression of the hypertrophy.     

卡维地洛对肥厚心肌能量代谢转换和结构重塑的作用研究

目的：研究卡维地洛对压力负荷性大鼠左室肥厚心肌中链脂酰辅酶A脱氢酶（MCAD）、肌型肉碱棕榈酰转移酶（M-CPT-I）和胶原结合蛋白（colligin）基因/蛋白表达变化的干预作用，阐明肥厚心肌能量代谢“胚胎型再演”和左室重塑的分子基础及卡维地洛心肌保护作用的可能机制。方法： 取健康雄性Wistar大鼠行腹主动脉缩窄（CAA）复制左室肥厚模型，取术后4周的大鼠随机分为腹主动脉缩窄（CAA）组和卡维地洛12周干预（CAR）组，设假手术（sham）组作为对照，以上每组均为12只，观察各组大鼠各项指标的变化。结果： （1）CAA组大鼠左心室湿重/体重、平均动脉压高于sham组；血清和心肌游离脂肪酸含量大于sham组；左室心肌M-CPT-I、MCAD mRNA的表达低于sham组，而colligin基因和蛋白表达高于sham组；（2）卡维地洛治疗12周后能逆转上述各项指标的变化。结论： （1）肥厚心肌脂肪酸的利用减少，能量代谢呈“胚胎型再演”， M-CPT-I和MCAD基因表达下调，可能是导致能量代谢“胚胎型再演”的分子基础；（2）卡维地洛能增加线粒体脂肪酸氧化关键酶M-CPT-I和MCAD基因的表达，促进心肌对脂肪酸的利用，对肥厚心肌能量代谢“胚胎型再演”有抑制作用；（3）卡维地洛抑制压力负荷诱导的colligin蛋白表达，抑制心肌纤维化。对心肌能量代谢模式和心室重塑的保护作用可能是卡维地洛治疗心力衰竭的重要作用机制。     

急性心肌梗死后心脏TGF-β1的表达和心室重塑(英文)

目的：探讨大鼠急性心肌梗死（AMI）后心肌纤维化和TGF-β1表达及炎症反应的分子机制。 方法： 建立大鼠AMI模型及假手术组，于术后第1、4和8周末测血流动力学后取心脏。RT-PCR和免疫组化SABC法检测TGF-β1基因和蛋白的表达。用氯胺T法测心肌组织羟脯氨酸的含量。心肌病检观察心肌组织炎症细胞浸润情况。 结果： 与假手术组相比，AMI后第1、4和8周末血流动力学有明显改变(P<0.01)。在梗死区、交界区和非梗死区羟脯氨酸和TGF-β1基因和蛋白表达均增高（P<0.05），第1周的表达高于第4和8周。羟脯氨酸和TGF-β1蛋白表达呈现明显正相关（r＝0.75－0.99，P<0.05）。AMI后第1周梗死区和交界区炎症细胞浸润明显，第4和8周心肌炎症细胞减少。TGF-β1在梗死后1周时主要见于心肌细胞、中性粒细胞、巨噬细胞和部分淋巴细胞的胞浆内表达，在4周和8周见于成纤维母细胞及间质。 结论： AMI后心肌细胞、炎症细胞、成纤维母细胞胞浆及基质中TGF-β1表达增高，与羟脯氨酸的变化及炎症过程存在联系，可能在AMI后心室重塑和心肌炎性修复过程中起重要作用。     

心肌肥厚大鼠左室组织中肌醇磷脂途径特征

本研究观察了心肌肥厚大鼠左室组织中肌醇磷脂途径特征。对大鼠行腹主动脉部分缩窄术制作心肌肥厚模型 ,术后 10d处死动物测全心重 体重比值 ,以免疫印迹法测左室组织Gαq 11和PLC β3 蛋白含量 ,以放免法测左室组织 1,4,5 三磷酸肌醇 (IP3 )含量。结果显示术后 10d时腹主动脉部分缩窄 (CA)组大鼠全心重 体重比值明显高于假手术 (SO)组 (P <0 0 1) ,二组大鼠左室组织Gαq 11和PLC β3 蛋白含量无显著差异 ,CA组左室组织IP3 浓度明显高于SO组 (P <0 0 5 )。上述结果提示肌醇磷脂途径可能参与压力超负荷性心肌肥厚病理过程     

心肌肥厚重塑的免疫机制研究进展

心血管疾病严重威胁人类健康,其继发的心肌肥厚和重塑是导致心脏功能逐渐恶化的关键因素.近年来,分子免疫学机制在心肌肥厚和重塑形成中的作用逐渐引起关注.研究多种细胞类型在心肌肥厚和重塑中的作用,如非心肌细胞,尤其是免疫细胞相互作用和炎症信号作用的机制,巨噬细胞、成纤维细胞和肾素-血管紧张素-醛固酮系统在心肌肥厚与重塑病理生理中的作用,对不同免疫细胞类型在心肌细胞肥大调控具有重要性以及潜在的治疗靶点.     

Left ventricular cellular hypertrophy in pressure- and volume-overload valvular heart disease

To determine the dependence of myocyte hypertrophy in chronic valvular heart disease on the site and type of lesion, the myocardium was studied from 11 patients with either pressure-overload hypertrophy (PO; four patients with aortic stenosis and two with mixed aortic stenosis/insufficiency) or pure volume-overload hypertrophy (VO; two patients with mitral regurgitation and three with aortic insufficiency). These patients, all without coronary artery disease, died zero to 34 days after valve replacement surgery. Diameters of 25 longitudinally oriented myocytes in the circular midwall myocardium were measured with a calibrated light microscope eyepiece reticle on each of five transmural, transverse, histologic sections from the apical, anterolateral, posterolateral, anteroseptal, and posteroseptal left ventricle. Statistical analysis by modified two-way analysis of variance (ANOVA) demonstrated that mean myocyte size (based on 125 measurements) varied widely among cases but was not statistically different among sites. The myocyte diameter for PO lesions (25.9 +/- 1.1 micron, mean +/- SEM) was significantly greater (P less than 0.05) than that for pure VO lesions (20.4 +/- 0.7 micron), despite equal relative heart weights (measured/predicted from body weight: 2.5 +/- 0.2 [mean +/- SD] versus 2.5 +/- 0.5). This study suggests that 1) cellular hypertrophy in valvular heart disease occurs uniformly throughout the left ventricular myocardium; and 2) mean myocyte diameters are greater in PO than in VO hypertrophy for equivalent cardiac enlargement.     

Augmented aftercontractions in papillary muscles from rats with cardiac hypertrophy.

Paired-pulse stimulation induced larger aftercontractions in papillary muscles from spontaneously hypertensive rats (SHR) than from normotensive Wistar-Kyoto rats (WKY). To determine whether aftercontraction exaggeration is a general characteristic of hypertrophied cardiac muscle, three models were examined: SHRs, deoxycorticosterone acetate (DOCA)-treated rats, and aorta-constricted rats. Responses of pipillary muscles from hypertrophied hearts tested under conditions conducive to aftercontraction generation were compared to pipillary muscles from WKY or sham-treated controls, respectively. Field-stimulated papillary muscles mounted in an oxygenated temperature-controlled physiologic salt solution were exposed to calcium concentrations of 2.5 and 5.0 mM, and temperatures of 27 degrees C and 17 degrees C. Although testing conditions influenced the contractile responses to single stimuli, there was no difference in active tension, time to peak tension, or one-half relaxation time between the three experimental groups and their respective controls. Paired-pulse stimulation induced aftercontractions that were enhanced in high-calcium and low-temperature solutions. Under these conditions, papillary muscles from hypertrophied hearts developed larger aftercontractions than did their respective controls.     

Right ventricular hypertrophy in monocrotaline pyrrole treated rats

Single, tail-vein injections of 2–4 mg/kg body weight of monocrotaline pyrrole produced an endothelial lesion in the cells lining the capillaries and arterioles of the rat lung. Within 4 weeks, numerous pulmonary vessels became partially or completely occluded by fibrin and platelet thrombi, by enlargement of the endothelium, and by hypertrophy of smooth muscle cells in the tunica media. Impairment of the pulmonary blood flow led to tissue hypoxia which was reflected by an increase in hemoglobin, hematocrit, and erythrocyte count values. In addition, there was a fourfold increase in peak systolic blood pressure within the lumen of the right ventricle. This hypertension was progressive and caused an increase in the workload of the right heart. Right ventricular hypertrophy developed gradually over 2–3 weeks so that by 4 weeks the right side of the heart weighed almost 3 times that of the controls. It is suggested that monocrotaline pyrrole injected animals provide a readily reproducible model for experimental cardiac hypertrophy which mimics the gradual onset of cardiac disease observed clinically in man.     

参松养心胶囊对糖尿病大鼠心室电生理特性及结构功能变化的影响

 目的：探讨参松养心胶囊（SSYX）对糖尿病（DM）大鼠心室电生理特性与结构功能变化的影响。方法：雄性SD大鼠45只,随机分为对照组（CTL组,n=15）、DM组（n=15）和SSYX组（n=15）。DM组和SSYX组采用一次性腹腔注射链脲佐菌素（60 mg/kg）制备糖尿病模型,CTL组则给予腹腔注射生理盐水（1 mL/kg）,72 h后检测血糖评价造模结果,将造模成功的动物纳入本研究。SSYX组连续6周给予SSYX灌胃（1 g·kg-1·d-1）治疗,DM组和CTL组则给予生理盐水灌胃（2 mL·kg-1·d-1）。动物完成药物治疗后,采用超声心动图检测心功能并记录II导联体表心电图;采用放射免疫法检测血浆的内皮素1（ET-1）水平;随后在整体心脏Langendorff灌流条件下行离体电生理研究,分别记录和测量左室前游离壁（LAF）心外膜单相动作电位（MAP）和有效不应期（VERP）,同时给予Burst快速电刺激用以进行室性心律失常（VA）的诱发;采用Masson染色对3组动物心肌纤维化程度进行评价。结果：与CTL组相比,DM组心功能下降（P<001）,而QT间期、VERP、动作电位时程、VA诱发率、心肌纤维化程度和血浆ET-1水平均增加（均P<001）;与DM组相比,SSYX组的心功能得到改善（均P<001）,且 QT间期、VERP、动作电位时程、VA诱发率、心肌纤维化程度和血浆ET-1水平均降低（均P<005）。结论：SSYX具有减轻DM大鼠心室电重构和结构重构及改善心功能的作用。     

扎考比利改善压力超负荷致大鼠心室重构的作用

目的:研究扎考比利(zacopride,ZAC)对腹主动脉缩窄所致大鼠压力超负荷性心室重构的改善作用。方法:通过腹主动脉缩窄构建大鼠压力超负荷心室重构模型,预防性给予ZAC、氯喹(chloroquine,Chlor)及ZAC+Chlor。连续给药8周,超声心动图评价心功能;计算心重/体重比(HW/BW)和左心室/体重比(LVW/BW);左心室心肌组织HE染色;透射电镜观察心肌细胞超微结构;Western blot检测大鼠心肌组织内向整流钾通道(IK1)蛋白表达;RT-PCR法检测心肌组织Kir2.1的mRNA表达。结果:与模型(vehicle)组相比,ZAC组大鼠心功能明显改善,LVEDS和LVEDD明显降低(P 0.05),LVEF和LVFS显著升高(P 0.01),HW/BW和LVW/BW显著降低(P 0.05),心肌肥大程度降低,心肌细胞横断面积明显减小(P 0.01),心肌超微结构明显改善。Chlor明显阻断了ZAC对腹主动脉缩窄所致压力超负荷大鼠心室重构的保护作用。与vehicle组相比,ZAC组大鼠心肌组织IK1蛋白表达和Kir2.1的mRNA显著升高(P 0.01)。结论:心肌IK1激动剂ZAC显著减轻大鼠左心室压力超负荷诱发的心室重构。     

Myocardial hypertrophy and enhanced left ventricular contractility in Zucker diabetic fatty rats.

Heart failure is known to be a complication of insulin-dependent (IDDM) and noninsulin-dependent diabetes mellitus (NIDDM) even in the absence of coronary heart disease or hypertension. The mechanisms leading to diabetic cardiomyopathy are unknown. The aim of the study was to characterize structural and functional alterations in hyperinsulinemic Zucker diabetic fatty (ZDF) rats treated with or without insulin. Diabetic animals showed a twofold increase in cardiomyocyte volume with increased left ventricular ANP but not BNP mRNA levels in spite of a reduced plasma renin activity (PRA) 2 months after onset of diabetes compared to nondiabetic littermates. These changes were associated with an increase in left ventricular performance as assessed by echocardiography. Insulin treatment led to a significant increase in body weight (BW), total heart weight, myocardial protein content, and left ventricular mass (LVM). Perivascular fibrosis and laminin thickness were significantly augmented in diabetic rat myocardium irrespective of insulin treatment, whereas interstitial collagen I and fibronectin were similarly found in diabetic and control myocardium. Initial stages of diabetic cardiomyopathy in hyperinsulinemic rats are characterized by cardiomyocyte hypertrophy and enhanced cardiac contractility. It is suggested that hyperinsulinemia may be involved in cardiac hypertrophy.     

Social stress, myocardial damage and arrhythmias in rats with cardiac hypertrophy.

In rat models of cardiac hypertrophy (moderate aortic coarctation: ACm, n=18; severe aortic coarctation: ACs, n=27; aging: OLD, n=25; spontaneous chronic hypertension: SHR, n=18) and properly matched control animals (C(ACm), n=17; C(ACs), n=19; C(OLD), n=24; C(SHR), n=22), we investigated the relative contribution of intense autonomic activity and cardiac structural damage to ventricular arrhythmogenesis. We used an "in vivo" to tissue level approach, by correlating in the same animal: (i) social stress-induced ventricular arrhythmias, telemetrically recorded, and (ii) left ventricular weights (LVW) and amount and geometrical properties of myocardial fibrosis (MF). Arterial blood pressure was significantly higher in ACm (+11%), ACs (+28%) and SHR (+34%) than in controls. LVW were approximately 20% greater in ACm, ACs and OLD and 50% greater in SHR. MF was about twice as great and characterized by more frequent occurrence of microscopic scarring in ACm and ACs, and eight times greater and associated with both a higher number and a larger size of fibrotic foci in OLD and SHR compared to controls. Social stress increased ventricular arrhythmia vulnerability in all models of cardiac hypertrophy, as well as in controls. The arrhythmogenic action of stress was facilitated in ACs, OLD and SHR. A correlation between structural cardiac remodeling and ventricular arrhythmias was found only in SHR and OLD, which exhibited the greatest increase in LVW and/or MF. Social stress proved to be a valuable tool for analyzing the combined effects of autonomic stimulation and altered myocardial substrate on the genesis of potentially life-threatening arrhythmias in social animals.     

PARP-2在大鼠心肌肥大中的作用

目的:在细胞和整体水平研究多聚腺苷酸二磷酸核糖基聚合酶2(PARP-2)在心肌肥大过程中表达的变化规律以及PARP-2对心肌肥大的调控作用。方法:健康雄性SD大鼠采用腹主动脉缩窄法(AAC)建立心肌肥大动物模型,采用real-time PCR和Western blot检测PARP-2的mRNA和蛋白表达变化;使用PARP-2特异性的siRNA干扰序列来处理细胞后,通过检测心肌细胞表面积及ANF、BNP和β-MHC的mRNA表达变化来作为评判心肌细胞肥大状况。结果:AAC大鼠心脏组织中PARP-2的蛋白和mRNA表达均显著上调;在AngⅡ诱导的心肌细胞肥大模型中,AngⅡ能时间和剂量依赖性地上调PARP-2的mRNA和蛋白表达;用siRNA干扰序列沉默PARP-2能够逆转AngⅡ所诱导心肌细胞的肥大。结论:在AngⅡ诱导的心肌细胞肥大的体外模型和腹主动脉缩窄诱导的心肌肥大动物的体内模型中,PARP-2的mRNA和蛋白水平均显著上调;特异性沉默PARP-2能够抑制AngⅡ诱导的心肌细胞肥大。     

Gene expression profiling of exercise-induced cardiac hypertrophy in rats

AIMS: Exercise training causes physiological cardiac hypertrophy, which acts to enhance cardiac function during exercise. However, the underlying molecular mechanisms are unclear. We investigated gene expression profile of exercise training-induced cardiac hypertrophy using left ventricle (LV) excised from exercise-trained and sedentary control rats (12-week old). METHOD: Rats in the training group exercised on a treadmill for 8-week. RESULTS: Left ventricular mass index and wall thickness in the exercise-trained group were significantly greater than that in the control group, indicating that the trained rats developed cardiac hypertrophy. Of the 3800 genes analysed in the microarray analyses, a total of 75 relevant genes (upregulation of 33 genes and downregulation of 42 genes) displayed alterations with exercise training. Among these genes, we focused on glycogen synthase kinase (GSK)-3beta, calcineurin-inhibitor (Cain), and endothelin (ET)-1 for their implicated roles in pathological cardiac hypertrophy, and confirmed the results of microarray analysis at mRNA and protein/peptide levels using quantitative PCR, Western blot, and EIA analyses. The gene expression of GSK-3beta decreased significantly and those of Cain and ET-1 increased significantly with exercise training. Furthermore, LV mass index was significantly correlated with GSK-3beta protein activity (r = -0.70, P < 0.01) and tissue ET-1 concentration (r = 0.52, P < 0.05). There were no changes in gene expressions in brain natriuretic peptide (BNP), angiotensin-correcting enzyme (ACE), interleukin-6, and vascular cell adhesion molecule (VCAM)-1. CONCLUSION: These findings suggest that physiological and pathological LV hypertrophy may share some of the same molecular mechanisms in inducing LV hypertrophy (e.g. GSK-3beta, Cain, and ET-1) and that other genes (e.g. BNP, ACE) may differentiate physiological from pathological LV hypertrophy.