大鼠心肌细胞的肌浆网与闰盘间偶联的电镜观察

本实验对大鼠心房心肌细胞的肌浆网与閏盘间的关系进行了超微结构观察。结果表明,肌浆网与閏盘的非特化肌膜存在偶联,为区别于一般的周围偶联,而将它们之间的偶联称为閏盘偶联。它具有周围偶联及内部偶联的形态结构特征,即(1)在偶联区域内存在胞浆间隙,宽约11～18nm;(2)在胞浆间隙内有连接突或连足;(3)肌浆网腔内含有电子致密物质。在偶联区域,肌浆网膜不仅与閏盘的非特化肌膜形成偶联,而且与线粒体外膜紧密并置。此外,心肌缝隙连接与肌浆网可形成缝隙连接-肌浆网偶联,其超微结构特点与心肌偶联相同。本文对肌浆网与閏盘的偶联的功能意义进行了讨论。     

膜磷脂成分对心肌肌浆网摄钙功能的影响

目的：观察膜磷脂成分改变对心肌肌浆网（ＳＲ）钙摄取功能的影响。方法：磷脂酶Ａ＿２或溶血磷脂分别与正常狗心肌ＳＲ温育，测定钙摄取量。结果：磷脂酶Ａ＿２可使ＳＲ摄钙量减少４８．８％（Ｐ＜０．０１），加入磷脂酰胆碱可部分逆转磷脂酶Ａ＿２造成的损伤。溶血磷脂酰胆碱或溶血磷脂酰丝氨酸显著抑制ＳＲ钙摄取。结论：磷脂酶Ａ＿２改变膜磷脂微环境，造成ＳＲ摄钙功能障碍可能是某些病理情况下，心肌细胞钙稳态失衡的原因之一。     

过氧化氢对兔心肌浆网膜流动性及钙—转移腺苷三磷酸酶活性的影响

用荧光偏振技术测定兔心肌浆网（ＳＲ）膜流动性，定磷法测定Ｃａ＾２＋－ＡＴＰａｓｅ活性，过氧化氢（Ｈ２Ｏ２）显降低ＳＲ膜流动性和Ｃａ＾２＋－ＡＴＰａｓｅ活性；荧光各向异性值与Ｃａ＾２＋－ＡＴＰａｓｅ活性变化呈负相关；过氧化氢酶（２０μｇ·Ｌ＾－１）完全取消Ｈ２Ｏ２（２ｍｍｏｌ·Ｌ＾－１）对ＳＲ的损伤作用，表明Ｈ２Ｏ２能直接损伤ＳＲ，膜流动性改变可能是Ｃａ＾２＋－ＡＴＰａｓｅ活性下降的原因之一。     

中长期模拟失重大鼠骨骼肌线粒体钙含量和肌浆网Ca~（2＋）－ATP酶活性变化

为探讨失重对肌肉功能的影响，观察了中长期模拟失重时大鼠骨骼肌细胞内Ｃａ２＋转运功能变化，测定了比目鱼肌、腓肠肌线粒体钙含量和肌浆网（ＳＲ）Ｃａ２＋－ＡＴＰａｓｅ活性。结果是悬吊１５、３０ｄ大鼠比目鱼肌和腓肠肌线粒体Ｃａ＋２含量增加，肌浆网Ｃａ２＋－ＡＴＰ酶活性降低，说明中长期模拟失重肌细胞内Ｃａ２＋转运功能发生了改变，这可能是影响肌肉收缩特性的因素之一。     

猫心肌缺血再灌注对Ca^2＋—ATPase活力及肌浆网钙摄取能力的 …

目的：观察猫心肌缺血再灌注过程中心肌细胞膜Ｃａ＾２＋－ＡＴＰａｓｅ活力、肌浆网钙摄取能力、线粒体丙二醛及心肌ＡＴＰ含量变化。方法：利用猫体外循环模型，心脏低温停搏６０ｍｉｎ后，恢复正常血液灌注６０ｍｉｎ。测定心肌细胞膜Ｃａ＾２＋－ＡＴＰａｓｅ活力、肌浆网钙摄取能力、心肌ＡＴＰ及线粒体丙二醛含量。结果：心脏缺血６０ｍｉｎ，随着心肌ＡＴＰ含量的下降，Ｃａ＾２＋－ＡＴＰａｓｅ活力及肌浆网钙摄取能力下降，     

卡托普利对缺血—再灌注心肌的保护作用

在大鼠心脏Ｌａｎｇｅｎｄｏｒｆｆ灌流模型上观察缺血－再灌注（Ｉ／Ｒ）时心肌局部血管紧张素ＩＩ（ＡＧＴＩＩ）的变化及卡托普利（ｃａｐｔｏｐｒｉｌ）对心肌保护作用。缺血３０ｍｉｎ后再灌注，心肌ＡＧＴＩＩ含量升高６０％，钙含量增加１．８倍，蛋白漏出明显增多，肌浆网（ＳＲ）的摄钙量减少５５％。ｃａｐｔｏｐｒｉｌ能有效抑制ＡＧＴＩＩ的生成，减轻心肌细胞损伤，并明显改善ＳＲ的摄钙功能，１０＾－９ｍｏｌ／Ｌ的Ａ     

肌浆网钙转运ATP酶和受磷蛋白在大鼠心肌梗死后的表达变化

目的建立大鼠急性心肌梗死模型,观察心肌梗死后心室重塑过程中肌浆网钙转运ATP酶(Ca-2+ATPase,SERCA)和受磷蛋白(PLB)的表达变化。方法雄性SD大鼠,应用前降支动脉结扎法建立大鼠心肌梗死模型,术后4周观察血流动力学参数,SERCA mRNA和PLB mRNA的表达。结果大鼠心肌梗死后4周,心肌梗死组左心室舒张末压(LVEDP)显著大于假手术组,左心室内压最大上升和下降速率(±dp/dtmax)显著低于假手术组。心肌梗死组心肌组织中SERCA mRNA表达下调,PLB mRNA表达上调。结论大鼠心肌梗死4周后心室收缩和舒张功能已降低,进入了心力衰竭阶段,SERCA mRNA和PLB mRNA的表达变化与心力衰竭的发生发展相关,可能是心肌梗死后心肌收缩和舒张功能失调的重要机制。     

阿霉素中毒大鼠膈肌骨架蛋白和肌浆网钙泵的表达变化及意义

目的观察不同剂量阿霉素诱导大鼠膈肌急性损伤时膈肌收缩特性的变化与大鼠膈肌细胞骨架蛋白和肌浆网钙泵表达变化的关系。方法一次性腹腔注射阿霉素制备急性膈肌损伤动物模型,♂SD大鼠随机分成:阿霉素低剂量组(10mg·kg-1)、中剂量组(20mg·kg-1)和高剂量组(40mg·kg-1)及对照组,每组10只。对照组用生理盐水腹腔注射。3d后剖胸取膈肌,应用体外灌流大鼠膈肌肌条方法,分别测量其单收缩张力(Pt)、最大强直张力(Po)、峰值收缩时间(CT)、半舒张时间(1/2RT),张力最大上升速度(+dt/dtmax)及张力最大下降速度(-dt/dtmax)。应用逆转录聚合酶链反应(RT-PCR)测定膈肌骨架蛋白肌联蛋白(titin)、伴肌动蛋白(nebulin)和肌浆网钙泵(sarcoplasmic reticulum Ca2+-ATPase,SERCA)mRNA的表达。结果与对照组相比,阿霉素中、高剂量模型组大鼠膈肌Pt,Po,±dt/dtmax下降(P<0.01),CT、1/2RT延长(P<0.01)。阿霉素中毒大鼠膈肌各基因表达较对照组相比分别降低(P<0.01)。结论阿霉素中毒大鼠膈肌细胞膈肌骨架蛋白titin、nebulin和SERCA mRNA表达下调,并可能与膈肌张力改变有关。     

慢性心衰大鼠心肌细胞内异常钙诱导钙释放的研究

目的研究慢性心衰大鼠心肌细胞内异常的钙诱导钙释放。方法将实验动物分为手术组和假手术组,运用全细胞膜片钳、激光扫描共聚焦显微镜、蛋白印迹（Western-blot）等方法研究胞浆内钙诱导钙瞬变及钙调控相关蛋白L-型钙通道（LTCC）表达的变化。结果慢性心衰大鼠心肌细胞肌浆网内的钙瞬变（ΔF/F0=12.72±1.13）显著低于对照组大鼠心肌细胞肌浆网内的钙瞬变（ΔF/F0=28.87±2.02,P〈0.01）;慢性心衰大鼠心肌细胞内LTCC的表达较对照组下调。结论 LTCC表达下调所致心肌兴奋-收缩耦联的异常是导致心衰的原因之一。     

过表达肌浆网钙ATP酶治疗实验性慢性缺血性心力衰竭

Objective Chronic myocardial ischemia (CMI) has become the most importat cause of heart failure (HF) all over the world. The aim of the current study was to investigate the effects of Sarcoendoplasmic reticulum calcium ATPaee 2a (SERCA2a) gene transfer on cardiac function and endoplasmic reticulum stress (ERS) associated myocardial apoptosis in a minipig HF animal model induced by CMI. Methods HF was induced in minipigs by implantation of ameroid constrictor in the initial segment of left anterior descending (LAD) branch of coronary artery. After confirmation of myocardial perfusion defects and cardiac function impairment by myocardial perfusion imaging and echocardiography, animals were divided into 4 groups (n =4 each): HF group, HF + enhanced green fluorescent protein (EGFP) group,HF + SERCA2a group, and shamed animals as control group. A total amount of 1×1012 v.g. Of rAAV1EGFP or rAAV1-SERCA2a were injected intramyocardially to each animal of HF + EGFP and HF +SERCA2a groups. Sixty days after gene transfer, protein level and activity of SERCA2a were examined,cardiac functions and changes of serum inflammatory and neuro-hormonal factors were determined. Apoptotic index of the ischemic myocardium, protein levels of ER stress marker glucose regulated protein 78 ( GRP 78) and ER stress specific apoptotic marker caspase-12 were also assayed. Results At the study end,echocardiographic and hemodynamic measurements indicated a significant improvement of both cardiac systolic and diastolic function in HF + SERCA2a group compared with HF/HF + EGFP groups [LVEF (60.2±8.6)%vs (44.2±7.1)% and (46.8±6.7)%, Ev/Ay 1.28±0.24 vs 0.77 ±0.17 and 0.80±0.21, +dp/dtmax(2713.9 ±434.0) mm Hg/s ( 1 mm Hg =0.133 kPa) vs (1892.3 ±434.2) mm Hg/s and (1931.2±397.4)mm Hg/s, -dp/dtmax (1422.1±334.4) mm Hg/s vs (848.3±308.3) mm Hg/s and (849.5±278.3)mm Hg/s, P＜0.05], along with increase in both SERCA2a protein level (1.13±0.26 vs 0.73 ±0.17 and 0.64±0.18, P＜0.05) and activity [(16.2±5.5) IU/ml vs (7.9±3.1) IU/ml and (7.5 ±2.8)IU/ml, P ＜0.05] compared with HF/HF + EGFP groups. Serum concentrations of inflammatory factor tumor necrotic factor α [(382.3±114.4) ng/L vs (732.3±201.4) ng/L and (689.8±192 5) ng/L, P＜0. 05], neural-hormonal factors brain natriuretic peptide [(142.6±45.3) ng/L vs (422.3±113.6) ng/L and(393.7 ±103.3)ng/L, P＜0.01], endothelin-1 [(111.4 ±37.5)ng/L vs (193.5 ±54.3)ng/L and (201.0±72.1)ng/L,P＜0.05] and angiotensin Ⅱ[(189.7±65.2)μg/L vs (538.3 ± 135.2) μg/L and ( 525.5±144.1)μg/L, P＜0.01] were also significantly decreased in HF + SERCA2a group compared with HF/HF + EGFP groups. The apoptotic index [(12.71±4.11)% vs(23.22±7.23) % and (24.31±6.38)%, P＜0.05], protein levels of GRP78 (1.27±0.33 vs 3.23±1.14 and 4.18±1.13, P＜0.05)and protein level ratios of cleaved caspase-12 to total caspase-12[(4.62±1.93)% vs (9.71±2.70)% and (10.14±2.81)%, P＜0.05] were also significantly reduced in the ischemic myocardium of HF+SERCA2a group compared with the HF/HF + EGFP groups. Conclusion Overexpression of SERCA2a significantly improved cardiac systolic and diastolic function in this HF model partly through attenuation of ER stress related myocardial apoptosis, suggesting its therapeutic potential for CM1 related heart failure.