运动对高血压性肥大心脏心肌肌球蛋白重链基因表达的影响

研究运动逆转高血压肥大心脏心肌肌球蛋白重链（ｍｙｏｓｉｎ ｈｅａｖｙ ｃｈａｉｎ ,ＭＨＣ）异型改变的分子机制。方法：采用Ｎｏｒｔｈｅｒｎ 分子杂交方法对自发性高血压大鼠（ｓｐｏｎｔａｎｅｏｕｓｌｙ ｈｙｐｅｒｔｅｎｓｉｖｅ ｒａｔｓ,ＳＨＲ） 游泳运动１０ 周后心肌ＭＨＣ基因表达进行比较研究。结果：游泳ＳＨＲ收缩压和舒张压分别比安静ＳＨＲ 降低２２ ％ 和２５％ （Ｐ＜ ０．０１） 。左心室重／体重（ＬＶＷ／ＢＷ）比值两组间无明显差异（Ｐ＞ ０．０５）。游泳ＳＨＲ 心肌αＭＨＣｍＲＮＡ表达比安静ＳＨＲ增强１７％ ,βＭＨＣｍＲＮＡ 表达降低２６ ％ ,α／βＭＨＣ基因表达比值提高５９ ％ 。结论：运动逆转高血压肥大心脏心肌ＭＨＣ同型异构体转变的调控机制可发生在基因转录水平上     

运动性和高血压性肥大心脏心肌肌膜乳酸转运特征比较

目的：探讨运动性和高血压性心肌肥大重塑时细胞表型代谢变化特征。方法：采用Ｌ－１４Ｃ乳酸盐测定运动Ｗｉｓｔａｒ大鼠,自发性高血压大鼠（ｓｐｏｎｔａｎｅｏｕｓｌｙ ｈｙｐｅｒｅｎｓｉｖｅ ｒａｔｓ,ＳＨＲ）、运动ＳＨＲ和对照Ｗｉｓｔａｒ Ｋｙｏｔｏ（ＷＫＹ）大鼠的心肌肌膜囊泡（ｓａｒｃｏｌｅｍｍａｌ ｖｅｓｉｃｌｅ,ＳＬＶ）单羧酸盐乳酸转运载体变化。结果：Ｗｉｓｔａｒ大鼠经每日２ｈ的１０周游泳运动后,     

自发性高血压大鼠运动后心肌c-fos和心钠素基因表达的变化

目的 :研究运动对高血压肥大心脏心肌初级和次级应答基因 (immediateearlygeneandlateresponsegene)表达的影响。方法 :采用Northern分子杂交方法对游泳运动 10周后自发性高血压大鼠 (spontaneouslyhypertensiverats ,SHR)心肌初级应答基因c fosmRNA和次级应答基因心钠素 (atrialnatriureticfactor ,ANF)mRNA的表达进行比较研究。结果 :游泳SHR收缩压和舒张压分别比安静SHR降低 2 2 %和 2 5 % (P <0 .0 1) ,但左心室重 /体重比值两组间无明显差异 (P >0 .0 5 )。SHR最后一次游泳 2 4h后 ,心肌c fosmRNA表达与安静SHR相比无明显差异 ,但两组大鼠比SHR的正常血压对照鼠WistarKyoto(WKY)分别提高 83 %和 80 %。游泳SHR心肌ANFmRNA表达比安静SHR降低 3 2 % ,但仍比WKY大鼠高 2 9%。结论 :SHR经过游泳运动后 ,出现心室肌ANF基因表达降低与c fos基因表达增强的不一致现象可能是运动改善高血压肥大心脏的分子机制之一。     

大鼠运动性肥大心脏心肌血管内皮生长因子及其基因表达的研究

目的和方法：血管内皮生长因子（ｖａｓｃｕｌａｒｅｎｄｏｔｈｅｌｉａｌｇｒｏｗｔｈｆａｃｔｏｒ,ＶＥＧＦ）是新近确定的一种特异作用于血管内皮细胞的活性肽。最近发现正常心肌细胞可表达ＶＥＧＦ,高血压肥大心脏心肌ＶＥＧＦ及基因表达增强,但对运动性心肌肥大时的变化尚不清楚。本实验采用免疫组化和分子杂交方法,对游泳运动１０周大鼠稳定期肥大心脏心肌ＶＥＧＦ及其基因表达进行研究。结果：ＷｉｓｔａｒＫｙｏｔｏ（ＷＫＹ）大鼠、自发性高血压大鼠（ｓｐｏｎｔａｎｅｏｕｓｌｙｈｙｐｅｒｔｅｎｓｉｖｅｒａｔｓ,ＳＨＲ）和运动大鼠心肌细胞浆内均有特异性ＶＥＧＦ染色颗粒,但运动大鼠心肌细胞胞浆内染色颗粒增加最明显。Ｎｏｒｔｈｅｒｎ分子杂交结果表明三组大鼠心肌均有ＶＥＧＦｍＲＮＡ表达,其中ＳＨＲ表达最强,运动大鼠比ＷＫＹ大鼠增强,但低于ＳＨＲ。结论：目前对这一结果的生理意义还不清楚,推测可能与心肌肥大时细胞间质血管增生有关。     

自发性高血压大鼠运动后心肌c—fos和心内素基因表达的变化

目的：研究运动地高血压肥大心脏心肌有和次级应答基因表达的影响。方法：Ｅｏｒｔｈｅｒｎ分子杂交方法对游泳运动１０周后自发性高血压大鼠心肌初级应答基因ｃ－ｆｏｓｍＲＮＡ和次级应答基因心钠素ｍＲＮＡ的表达进行比较研究。结果：游泳ＳＨＲ收缩压和坟分别比安静ＳＨＲ降低２２％和２５％，但左心室重／体重比值两组间无明显差异。ＳＨＲ最后一次游泳２４ｈ后，心肌ｃ－ｆｏｓｍＲＮＡ表达与安静ＳＨＲ相比无明显差异，但两组     

大鼠运动性肥大心脏心肌血管内皮生长因子及其基因表达 …

目的和方法：血管内皮生长因子（ｖａｓｃｕｌａｒｅｎｄｏｔｈｅｌｉａｌｇｒｏｗｔｈＶＥＧＦ）是新近确定的一种特异作用血管内皮细胞的活性肽。最近发现正常心肌细胞可表达ＶＥＧＦ高血压肥大心脏恼肌ＶＥＧＦ及其因表达增强,但对运动性心肌肥大时的变化尚不清楚,本实验采用免疫组分和分子杂交方法,对游泳运动１０周大鼠稳定期肥大心脏心肌ＶＥＧＦ及其基因表达进行了研究,结果：ＷｉｓｔａｒＫｙｏｔｏ（ＷＫＹ）大鼠,自发     

开搏通对游泳大鼠心肌肥大的影响

为了明确开搏通对运动性心肌肥大的作用。本实验采用游泳训练引起的大鼠心肌肥大模型,应用放射免疫及生化等方法对心肌肥大及心脏肾素－血管紧张素系统（Ｒ－Ａ－Ｓ）的变化进行了初步研究。观察到游泳五周时,大鼠心重／体重比值（Ｈ／Ｂｗｔ）显著升高,同时心肌血管紧张素Ⅱ（ＡｎｇⅡ）及心肌血管紧张素转换酶（ＡＣＥ）也明显升高。而服用开搏通的游泳大鼠心肌ＡｎｇⅡ,ＡＣＥ较单纯游泳组低,但心重／体重比值却升高。上述结果提示开搏通能抑制运动所致心肌ＡｎｇⅡ升高,但不能防止运动引起的心肌肥大。     

运动性和主血压性心肌肥大肌浆网Ryanodine受体变化特？…

为进一步了解运动性和病理心肌肥大重塑的不同特征。方法：采用＾３Ｈ－Ｒｙａｎｏｄｉｎｅ配体结合方法,对游泳运动和压力负荷高血压心肌肥大大鼠心肌肌浆网Ｒｙａｎｏｄｉｎｅ受体变化特征进行了比较研究。结果;与对照组相比,大鼠行腹主动脉狭窄术后６周,血压和心系分别升高６２％和４５％,心肌肌浆网每毫克蛋白高亲和最大结合降低４０％,低亲和／高亲和Ｂｍａｘ升高４２％,高亲和受体与配体的解离常数值降低１１％,肌浆网     

左旋硝基精氨酸诱导的高血压大鼠心肌和血管的肾上腺髓质素与受体活性修饰蛋白2表达的变化

探讨高血压大鼠心肌和血管的肾上腺髓质素（adrenomedullin,ADM）与受体活性修饰蛋白2（receptoractivity-modifying protein 2,RAMP2）mRNA的变化。用一氧化氮合酶（NOS）竞争性抑制剂左旋硝基精氨酸（L-NNA）阻断NOS制备大鼠高血压模型。用放射免疫分析方法测定血浆、心肌和血管ADM含量,及竞争性定量RT-PCR方法测定心肌和血管ADM mRNA与RAMP2 mRNA含量。结果表明,NOS阻断剂L-NNA应用4周后动物血压明显升高、心肌肥厚。心重（mg）/体重（g）比值增加35.5％（P<0.01）。血浆、心肌和血管的ADM-ir较对照组分别增加80％、72％和57％（均P<0.01）。高血压大鼠心肌和血管ADM mRNA含量显著增加,分别较正常大鼠高50％（P<0.05）和102.9％（P<0.05）。高血压大鼠心肌和血管的RAMP2　mRNA含量均显著增加,分别较正常大鼠高132％（P<0.01）和87％（P<0.01）。高血压大鼠心肌和血管ADM的升高与RAMP2的升高程度呈明显的正相关,其相关系数分别为0.741和0.885。上述观察结果表明,高血压时血浆、心肌和血管ADM水平升高,心肌和血管ADM与RAMP2基因表达上调,提示ADM/RAMP2系统在高血压发病中可能具有重要作用。     

力竭性运动后大鼠血清CK、CK-MB活性和心肌组织形态学的动态改变

目的：探讨一次和反复力竭性运动后不同时相大鼠血清肌酸激酶（CK）、肌酸激酶同工酶（CK-MB）与心肌损伤的变化规律。方法：通过力竭性游泳制备运动性心肌损伤模型,分别于运动后即刻和3 h6、h、12 h2、4 h4、8 h、96 h检测血清CK、CK-MB活性,并观察心肌组织形态学的动态变化。结果：大鼠一次力竭运动后0~12 h,CK和CK-MB活性明显增加,6 h达高峰;心肌炎细胞浸润灶逐渐增多,胞质嗜酸性增强,损伤高峰在12 h左右。反复力竭运动后0~12 h和48 h9、6 h CK和CK-MB活性皆明显增加,分别于运动后即刻和96 h达高峰;心肌细胞均有不同程度的损伤,48 h最严重。结论：过度运动和/或力竭性运动皆引起运动性心肌损伤,同时存在延迟性心肌损伤。     

Effects of salt loading and various therapies on cardiac hypertrophy and fibrosis in young spontaneously hypertensive rats

We investigated the effects of salt loading on blood pressure, cardiac hypertrophy and fibrosis as well as on the effectiveness of various antihypertensive therapies in young spontaneously hypertensive rats (SHR). Twenty-five male SHR were salt-stimulated by drinking 1% NaCl from 3 to 6 months of age. Eighteen of them were treated for the last 2 weeks of salt loading with either the angiotensin-converting enzyme inhibitor captopril, the beta-adrenergic receptor blocker propranolol or the calcium-channel antagonist verapamil. Age-matched male Wistar-Kyoto (WKY) rats and SHR drinking only water served as controls. At the age of 6 months, SHR had significantly elevated blood pressure that was unchanged by salt loading. Relative heart weight was increased in SHR without (3.3) and even more so with salt intake (3.6 vs. 2.4 in WKY). Left ventricular (LV) hypertrophy was accompanied by a 17-fold increase in the expression of mRNA for atrial natriuretic factor (ANF) both in untreated and salt-loaded SHR compared to WKY (p<0.001). Collagen I and III mRNA increased 1.7-1.8-fold in SHR without and with additional salt intake (p<0.01). None of the therapies significantly reduced blood pressure or hypertrophy. Although captopril had no antihypertensive effect, it reduced ANF, collagen I and III mRNA in LV to control level. Less pronounced effects were achieved with verapamil. These findings emphasize the cardioprotective role of captopril which may not be fully expressed in the presence of elevated salt intake.     

Increased expression of IL-6 and LIF in the hypertrophied left ventricle of TGR(mRen2)27 and SHR rats

Cytokines from the interleukin-6 (IL-6) family have been reported to play an important synergistic role with angiotensin II in the development of pathological cardiac hypertrophy. Whether their expression pattern changes in vivo, in an angiotensin II-dependent hypertrophied myocardium has not been reported. In this study, we addressed that issue using two animal models of angiotensin II-dependent cardiac hypertrophy. Heterozygous transgenic TGR(mRen2)27 (TGR) with an overactive cardiac renin angiotensin system and the closely related spontaneously hypertensive rats (SHR) were compared to their respective control rats. The mRNA levels of IL-6, leukemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF) and cardiotrophin-1 (CT-1) as well as their receptor subunits, glycoprotein 130 (gp130), IL-6 receptor (IL-6R), LIFR, and CNTFR, were measured by semi-quantitative RT-PCR. The protein levels of IL-6, LIF and CT-1 were investigated by western blot. TGR and SHR both displayed significant over expression of mRNA and protein levels for IL-6 and LIF. In TGR, the increased level of LIF was accompanied by a decrease in mRNA levels for LIFR and CNTFR. In SHR, a higher level of mRNA IL-6R was observed. By contrast, the mRNA and protein levels for CT-1 and the mRNA level for gp130 did not vary in these two models. These findings suggest that IL-6 and LIF, but not CT-1, contribute to angiotensin II-dependent left ventricular hypertrophy in the two hypertensive rat models, TGR(mRen2)27 and SHR. (Mol Cell Biochem 269: 95–101, 2005)     

Altered molecular response to adrenoreceptor-induced cardiac hypertrophy in Egr-1-deficient mice

Unmanipulated early growth response-1 (Egr-1)-deficient -/- mice have similar heart-to-body weight ratios but express lower amounts of atrial natriuretic factor (ANF), beta-myosin heavy chain (beta-MHC), skeletal actin, NGF1-A binding protein (NAB)-2, Sp1, c-fos, c-jun, GATA-4, and Nkx2.5 than +/+ or +/- mice. alpha-MHC, tubulin, and NAB-1 expression was similar. Isoproterenol (Iso) and phenylephrine (PE) infusion into +/+ and -/- mice increased heart weight, ANF, beta-MHC, skeletal actin, Sp1, NAB-2, c-fos, and c-jun expression, but induction in -/- mice was lower. Only Iso + PE-treated +/+ mice showed induction of NAB-1, GATA-4, and Nkx2.5. Foci of fibrosis were found in Iso + PE-treated -/- and +/+ mice. Surprisingly, vehicle-treated -/- mice displayed fibrosis and increased Sp1, skeletal actin, Nkx2.5, and GATA-4 expression without hypertrophy. Minipump removal caused the agonist-treated hearts and gene expression to regress to control or near-control levels. Thus Egr-1 deficiency caused a blunted catecholamine-induced hypertrophy response and increased sensitivity to stress.     

Down-regulation of mitofusin-2 expression in cardiac hypertrophy in vitro and in vivo

Mitofusin-2 (Mfn2) suppresses smooth muscle cell proliferation through inhibition of the Ras-extracellular signal-regulated kinases (ERK1/2) pathway. Since the ERK1/2 pathway is implicated in mediating hypertrophic signaling, we studied the changes in Mfn2 in cardiac hypertrophy using in vitro and in vivo models. Phenylephrine was used to induce hypertrophy in neonatal rat ventricular myocytes (NRVMs). In vivo hypertrophy models included spontaneously hypertensive rats (SHR), pressure-overload hypertrophy by transverse aortic constriction (TAC), hypertrophy of non-infarcted myocardium following myocardial infarction (MI), and cardiomyopathy due to cardiac-restricted overexpression of beta(2)-adrenergic receptors (beta(2)-TG). We determined hypertrophic parameters and analysed expression of atrial natriuretic peptide (ANP) and Mfn2 by real-time PCR. Phosphorylated-ERK1/2 (phospho-ERK) was measured by Western blot. Mfn2 was downregulated in phenylephrine treated NRCMs (by approximately 40%), hypertrophied hearts from SHR (by approximately 80%), mice with TAC (at 1 and 3 weeks, by approximately 50%), and beta(2)-TG mice (by approximately 20%). However, Mfn2 was not downregulated in hypertrophied hearts with 15 weeks of TAC, nor in hypertrophied non-infarcted myocardium following MI. phospho-ERK1/2 was increased in hypertrophied myocardium at 1 week post-TAC, but not in non-infarcted myocardium after MI, indicating that downregulated Mfn2 may be accompanied by an increase of phospho-ERK1/2. This study shows, for the first time, downregulated Mfn2 expression in hypertrophied hearts, which depends on the etiology and time course of hypertrophy. Further study is required to examine the causal relationship between Mfn2 and cardiac hypertrophy.     

Increased mRNA expression of cardiac renin-angiotensin system and collagen synthesis in spontaneously hypertensive rats

Hypertensive cardiac hypertrophy is associated with the accumulation of collagen in the myocardial interstitium. Previous studies have demonstrated that this myocardial fibrosis accounts for impaired myocardial stiffness and ventricular dysfunction. Although cardiac fibroblasts are responsible for the synthesis of fibrillar collagen, the factors that regulate collagen synthesis in cardiac fibroblasts are not fully understood. We investigated the effects of angiotensin II on cardiac collagen synthesis in cardiac fibroblasts. Cardiac fibroblasts of 10 week old spontaneously hypertensive rats and age-matched Wistar-Kyoto rats were prepared and maintained in culture medium supplemented with 10% fetal calf serum. The expression of mRNA of the renin-angiotensin system (renin, angiotensinogen, angiotensin converting enzyme) was determined by using a ribonuclease protection assay. Basal collagen synthesis in cardiac fibroblasts from spontaneously hypertensive rats was 1.6 fold greater than that in the cell of Wistar-Kyoto rats. Angiotensin II stimulated collagen synthesis in cardiac fibroblasts in a dose-dependent manner. The responsiveness of collagen production to angiotensin II was significantly enhanced in cardiac fibroblasts from spontaneously hypertensive rats (100 nM angiotensin II resulted in 185 ± 18% increase above basal levels, 185 ± 18 versus 128 ± 19% in Wistar-Kyoto rats p < 0.01). This effect was receptor-specific, because it was blocked by the competitive inhibitor saralasin and MK 954. These results indicate that collagen production was enhanced in cardiac fibroblasts from spontaneously hypertensive rats, that angiotensin II had a stimulatory effect on collagen synthesis in cardiac fibroblasts, and that cardiac fibroblasts from spontaneously hypertensive rats were hyper-responsive to stimulation by angiotensin II.Level of angiotensin and renin mRNA expressed in ventricles, and angiotensinogen mRNA expressed in fibroblasts from SHR were higher than those from WKY.These findings suggest that the cardiac renin-angiotensin system may play an important role in collagen accumulation in hypertensive cardiac hypertrophy.     

TGF-beta(1) and prepro-ANP mRNAs are differentially regulated in exercise-induced cardiac hypertrophy.

The induction of transforming growth factor (TGF)-beta and prepro-atrial natriuretic peptide (ANP) mRNAs represent hallmark features of pathological cardiac hypertrophy. The present study examined whether this pattern of mRNA expression was conserved in a physiological model of cardiac hypertrophy. To address this thesis, female Sprague-Dawley rats were individually housed and permitted to run freely. Voluntary exercise for 3 and 6 wk resulted in biventricular hypertrophy and increased cytochrome c oxidase activity in the triceps muscle. In the hypertrophied left ventricle, the steady-state mRNA level of the cardiac fetal gene prepro-ANP and the extracellular matrix proteins preprocollagen-alpha(1) and fibronectin were similar in exercise-trained and sedentary rats. By contrast, an increased expression of TGF-beta(1) mRNA was observed, whereas TGF-beta(3) mRNA level was unchanged in the hypertrophied left ventricle of exercise-trained compared with sedentary rats. These data highlight a heterogeneity in the regulation of TGF-beta isoforms, and the increased expression of ventricular TGF-beta(1) mRNA in physiological cardiac hypertrophy may contribute to myocardial remodeling.     

Ubiquinol-cytochrome-c reductase 7.2 kDa protein of mitochondrial complex III is steroid-responsive and increases in cardiac hypertrophy and hypertension

Women and men do not respond identically to cardiac insults; premenopausal women are somewhat protected from cardiovascular disease. Our objective was to isolate and characterize hormone-responsive genes in the heart. Differential display identified an estrogen-inducible fragment that was found to encode the ubiquinol-cytochrome-c reductase (UCCR) 7.2 kDa protein of the mitochondrial respiratory complex III. We found UCCR7.2 mRNA to be highly expressed in the heart, and this expression increased in hearts of 4-, 10-, and 28-week-old spontaneously hypertensive rats (SHR) compared with normotensive Wistar-Kyoto rats. Oral hydralazine treatment to reduce hypertension reduced SHR UCCR7.2 expression. Cardiac UCCR7.2 mRNA expression was also increased significantly after a 5/6 nephrectomy compared with mock surgery. Cardiac expression after ovariectomy was 50% that of intact rats. Supplementation of ovariectomized rats with estrogen had no effect, whereas progesterone increased cardiac expression, although not to intact levels. No change in cardiac UCCR7.2 expression was found when intact rats were treated with either tamoxifen or ICI 182780. Thus, UCCR7.2 expression is reduced in the absence of ovarian hormones, but is not directly regulated by estrogen in the heart. We conclude that UCCR7.2 is a steroid hormone-responsive gene in the heart, with expression increased in cardiac hypertrophy and in response to hypertension.