缬沙坦与硝苯地平对自发性高血压大鼠左心室肥厚心肌细胞G 蛋白偶联受体激酶2的表达及亚细胞分布的影响

目的 观察缬沙坦及硝苯地平对自发性高血压大鼠(SHR)左心室肥厚心肌细胞G 蛋白偶联受体激酶2(GRK2)的表达及亚细胞分布的影响.方法 选择自发性高血压大鼠(SHR)为研究对象(n=30),随机分为对照组(n=6),低剂量缬沙坦组[L 缬沙坦,10 mg /(kg·d),n=6],高剂量缬沙坦组[H缬沙坦,30 mg /(kg·d),n=6],低剂量硝苯地平组[L 硝苯地平,10 mg /kg,2 次/ d,n=6],高剂量硝苯地平组[H 硝苯地平,30mg /(kg·次),2 次/d,n=6],由6 月龄喂养至8月龄,处死后分离心脏,通过免疫荧光标记、激光共聚焦显微镜及Werstern Blot 等方法,观察左心室心肌细胞GRK2的表达及亚细胞分布的变化.结果 与对照组比较,两药物干预的SHR 左心室心肌细胞膜蛋白GRK2表达及分布减少,高剂量较低剂量又有进一步减少,差异均有统计学意义(均P＜0.05).缬沙坦组左心室心肌细胞膜蛋白GRK2表达及左心室重量较硝苯地平组减少,差异有统计学意义(P＜0.05).相关性分析结果示两药物干预组大鼠左心室心肌细胞膜蛋白GRK2透光密度与左心室重量呈正相关(缬沙坦组r＝0.837,硝苯地平组r＝0.829,均P＜0.01).结论 缬沙坦与硝苯地平改善左心室肥厚可能与抑制SHR 左心室心肌细胞膜蛋白GRK2表达有关,缬沙坦较硝苯地平能更好地改善心肌肥厚可能与其抑制GRK2表达使其进一步减少有关.     

缬沙坦对自发性高血压大鼠左心室肥厚心肌细胞GRK2的表达及亚细胞分布的影响

目的观察缬沙坦对自发性高血压大鼠（SHR）左心室心肌细胞G蛋白偶联受体激酶2（GRK2）的表达及亚细胞分布的影响。方法18只SHR随机分为对照组（n=6）,低剂量缬沙坦组[SHRL组,10mg/（kg·d）,n=6]和高剂量缬沙坦组[SHRH组,30mg/（kg·d）,n=6],由6月龄喂养至8月龄,处死后分离心脏,通过免疫荧光标记、激光共聚焦显微镜及Werstern blot方法,观察左心室心肌细胞GRK2的表达及亚细胞分布的变化。结果与对照组比较,SHRL组及SHRH组左心室心肌组织总蛋白、浆蛋白及膜蛋白GRK2表达水平有明显减少（P＜0.05）,SHRH组较SHRL组减少更明显（P＜0.05）;与对照组比较, SHRL组及SHRH组GRK2在心肌细胞膜上分布减少,SHRH组较SHRL组进一步减少。结论缬沙坦能减少SHR左心室心肌细胞GRK2的表达及在细胞膜上的分布,这可能是逆转心肌肥大及心室重塑的机制之一。     

高血压大鼠左心室肥大心肌细胞中Src激酶膜转位的研究

目的:探讨Src激酶在高血压所致左心室肥大发病机制中的作用。方法: 以自发性高血压大白鼠(SHR)为研究对象,通过免疫荧光标记、共聚焦显微镜观察及蛋白质印迹等方法,检测不同月龄的SHR左心室肥大心肌细胞中Src激酶的表达和定位的变化。结果: 蛋白质印迹检测显示,Src激酶在2、6、12和18月龄的SHR组左心室心肌组织抽提的总蛋白匀浆中的表达量与相同月龄的对照Wistar-kyoto(WKY)大鼠组相比较,无明显变化;而在其抽提的胞质蛋白匀浆中和膜蛋白匀浆中,2月龄的SHR组与对照WKY大鼠组相比较,Src激酶的表达无明显差别,但将6、12、18月龄的SHR组分别与相同月龄的WKY大鼠组比较,在胞质蛋白匀浆中Src激酶的表达显著减少(P<0.05),在膜蛋白匀浆中Src的表达则显著增加(P<0.05)。免疫荧光标记也显示,在6、12和18月龄的SHR心肌细胞中出现一些定位变化,主要表现为Src激酶在心肌细胞闰盘的聚集,在心肌细胞闰盘处可观察到较宽的明亮荧光带,这些变化正好与SHR左心室肥大心肌细胞失代偿性重构相吻合。结论:研究结果表明,在高血压所致失代偿性心肌肥大形成和发展的全过程中,存在Src激酶的膜转位,提示心肌细胞中Src激酶信号转导通路可能参与了高血压所致失代偿性左心室肥大的心肌重构过程。     

厄贝沙坦对自发性高血压大鼠心肌Janus激酶-信号转导和转录活化因子信号通路的影响

目的 探讨厄贝沙坦对自发性高血压大鼠(SHR)心肌组织Janus激酶-信号转导蛋白和转录激活蛋白(JAK-STAT)信号转导通路及细胞凋亡的影响. 方法 30周龄WKY大鼠13只,设为WKY对照组;30周龄SHR 26只,随机分为SHR对照组和厄贝沙坦组.反转录-聚合酶链反应(RT-PCR)法检测血管紧张素Ⅱ1型(AT1)与2型(AT2)受体mRNA在心肌中的表达,免疫组化法检测心肌组织STAT1、STAT3表达,TUNEL细胞凋亡显色法进行细胞凋亡检测. 结果 (1)厄贝沙坦组与SHR对照组比较,AT1 mRNA表达水平显著降低(0.72±0.55对1.08±0.13,P<0.01),AT2 mRNA表达水平显著增高(0.30±0.32对0.25±0.35,P<0.01);(2)与SHR对照组比较,厄贝沙坦能降低STAT1表达(7.27±0.53对13.16±0.35,P<0.01),升高STAT3表达(5.41±0.37对4.82±0.34,P<0.01);(3)厄贝沙坦组心肌细胞凋亡率显著低于SHR对照组(P<0.01). 结论厄贝沙坦能调节心肌组织JAK-STAT信号转导通路,抑制细胞凋亡,从而发挥其心脏保护作用.     

自发性高血压大鼠心肌细胞蛋白激酶C活性的变化及其与心肌细胞凋亡的关系

目的 :研究自发性高血压大鼠 (SHR)心肌细胞蛋白激酶 C(PKC)活性的动态变化及其与心肌细胞调亡的关系。　　方法 :将 17只 SHR分为 3组 :1月龄 SHR组 (n=6 )、10月龄 SHR组 (n=6 )和 18～ 2 0月龄 SHR组 (n=5 )。每组均等数按鼠龄、体重及雌雄配对配予 WKY大鼠做对照。采用同位素法、电镜技术和末端脱氧核糖核苷酸转移酶介导的脱氧三磷酸尿苷缺口末端标记法检测 SHR左心室心肌细胞 PKC活性和心肌细胞凋亡的变化。采用直线回归分析确定PKC活性与心肌细胞凋亡的关系。　　结果 :11月龄 SHR组和 18～ 2 0月龄 SHR组心肌细胞膜 PKC活性显著低于同龄 WKY大鼠组 ,而心肌细胞凋亡却显著高于同龄 WKY大鼠组 (P均 <0 .0 1) ;但 10月龄 SHR组心肌细胞膜 PKC活性显著高于同龄 WKY大鼠组、1月龄 SHR组和 18～ 2 0月龄 SHR组而心肌细胞凋亡却显著低于同龄 WKY大鼠组 (P均 <0 .0 1) ;各组间心肌细胞浆 PKC活性无显著性差异 (P均 >0 .0 5 )。 2 SHR心肌细胞膜 PKC活性与心肌细胞凋亡指数呈显著负相关 (P<0 .0 5 ) ,但心肌细胞浆 PKC活性与心肌细胞凋亡指数不相关 (P>0 .0 5 )。　　结论 :心肌细胞膜 PKC活性降低可能与 SHR心肌细胞凋亡增加和充血性心力衰竭相关 ,而心肌细胞膜 PKC活性增加可能与 SHR心肌细胞凋亡减少和     

自发性高血压大鼠肥厚左室心肌组织微小RNA-1与内向整流钾通道2.1表达的改变及其意义

目的观察自发性高血压大鼠(SHR)肥厚的左室心肌组织微小RNA-1、内向整流钾通道2.1(Kir2.1)表达的变化及其关系,以探讨高血压左心室肥厚(LVH)发生室性心律失常的分子机制。方法取10只17周龄雄性SHR为LVH组,10只8周龄雄性SHR为阳性对照组,10只17周龄雄性WKY大鼠作为空白对照组,通过HE染色、心肌细胞横径测量、实时荧光定量聚合酶链反应(qRT-PCR)、免疫组织化学法及Western blot检测等方法,检测大鼠左室心肌组织病理学改变、微小RNA-1表达、Kir2.1蛋白表达水平的改变。结果①与空白对照组比较,LVH组和阳性对照组的收缩压、舒张压明显升高(分别P<0.01,P<0.05);②与两对照组相比,LVH组的左室质量指数及心肌细胞横径均明显增大(均P<0.05),左室心肌细胞明显肥大,心肌间质增多,伴随着微小RNA-1表达水平明显升高,Kir2.1蛋白表达水平显著降低(P<0.05);③LVH组大鼠左室心肌组织微小RNA-1与Kir2.1蛋白的表达水平呈负相关(r=-0.720,P<0.05)。结论SHR肥厚左室心肌组织微小RNA-1表达上调,并伴随Kir2.1表达下调。     

氯沙坦对自发性高血压大鼠心脏血管紧张素转换酶2-血管紧张素(1～7)-MAS-ERK通路的影响

目的探讨氯沙坦对自发性高血压大鼠(SHR)心肌中血管紧张素转换酶2(ACE2)-血管紧张素(1～7)[Ang(1-7)]-MAS-ERK通路的影响。方法30周龄SHR随机分为SHR组(n=11)、氯沙坦组[氯沙坦灌胃30mg/(kg·d),n=12],以Wistar大鼠(WKY)作正常对照(n=12)。处理12周后,应用放射免疫法检测大鼠血浆及心肌组织血管紧张素Ⅱ(AngⅡ)、血管紧张素(1～7)[Ang-(1-7)]水平;采用RT-PCR法检测各组大鼠心肌血管紧张素转换酶(ACE)、ACE2和MAS受体mRNA水平;采用Western blot法检测ACE、ACE2和磷酸化细胞外信号调节激酶(pERK1/2)蛋白表达水平。结果用药12周后,氯沙坦组血压明显低于SHR组[(164.3±21.6)比(241.3±24.5)mmHg,P<0.01];SHR组心肌ACE mRNA和蛋白表达水平显著高于WKY组,而ACE2 mRNA和蛋白表达、心肌MAS受体mRNA表达水平明显低于WKY组,差异有统计学意义(P<0.01);氯沙坦组ACE2 mRNA和蛋白表达、MAS mRNA表达水平高于SHR组(P<0.01),心...     

心脏肥大细胞在自发性高血压大鼠心肌重构中的作用

目的探讨心脏肥大细胞在自发性高血压大鼠(SHR)心肌重构中的作用.方法应用病理检查、计算机分析结合逆转录-聚合酶链式反应等方法,观察SHR及Wistar-Kyoto大鼠(WKY)收缩压、左室重量指数、心肌细胞直径、肥大细胞密度、心肌胶原容积分数(CVF)、心肌血管周围胶原面积比(PV-CA)和心肌Ⅰ、Ⅲ型胶原mRNA表达水平的变化.肥大细胞密度与左室重量指数、CVF及PVCA之间的关系采用相关分析.结果与WKY比较,SHR收缩压为(206±18)比(108±10)mm Hg(P<0.01);SHR组左室重量指数为(4.6±0.4)比(3.3±0.3)mg/g,(P<0.01);SHR组心肌细胞长径为(17.4±1.9)比(10.0±2.2)μm(P<0.01);SHR组心肌细胞短径为(9.0±2.0)比(5.8±1.7)μm(P<0.01);SHR组肥大细胞密度为(7.4±3.2)比(1.9±1.2)个/mm2(P<0.01),SHR组肥大细胞密度为WKY组的3.9倍.SHR组CVF、PVCA分别为46.4%±7.8%和1.9±0.9,WKY组分别为24.4%±10.7%和0.4±0.1,SHR组明显升高(P<0.01).SHR组心肌Ⅰ、Ⅲ型胶原mRNA表达相对含量也均明显高于WKY(P<0.01),心脏肥大细胞密度与左室重量指数、CVF及PVCA存在明显的正相关(相关系数分别为0.67、0.87和0.95,P<0.01).结论心脏肥大细胞密度增加可能是促进SHR心肌重构的重要原因.     

夏膝颗粒对自发性高血压大鼠心肌TGF-β1表达的影响

目的 探讨夏膝颗粒对自发性高血压大鼠(SHR)心肌转化生长因子(TGF-β1)表达的影响及意义.方法 50只12周龄雄性SHR随机分为5组:SHR空白组、阳性药组、夏膝颗粒高、中、低剂量组各10只,分别予以缬沙坦和不同剂量的夏膝颗粒灌胃;同时选取8只同周龄的雄性Wistar-Kyoto大鼠(WKY)作为对照.给药8 w后采用RT-PCR法检测心肌TGF-β1 mRNA水平. 结果与WKY对照组比较,SHR空白组心肌TGF-β1/β-actin吸光值之比显著升高(P<0.01);与SHR空白组比较,夏膝颗粒高剂量组能显著降低SHR TGF-β1 mRNA的表达(P<0.01),甚至低于WKY组(P<0.05).结论 夏膝颗粒可能通过下调心肌TGF-β1的高表达,抑制心肌细胞外基质的增生,防止心室重构.     

心脏肥大细胞在自发性高血压大鼠心肌重构中的作用

目的探讨心脏肥大细胞在自发性高血压大鼠(SHR)心肌重构中的作用。方法应用病理检查、计算机分析结合逆转录聚合酶链式反应等方法,观察SHR及Wistar-Kyoto大鼠(WKY)收缩压、左室重量指数、心肌细胞直径、肥大细胞密度、心肌胶原容积分数(CVF)、心肌血管周围胶原面积比(PV-CA)和心肌Ⅰ、Ⅲ型胶原mRNA表达水平的变化。肥大细胞密度与左室重量指数、CVF及PVCA之间的关系采用相关分析。结果与WKY比较,SHR收缩压为(206±18)比(108±10)mm Hg(P<0.01);SHR组左室重量指数为(4.6±0.4)比(3.3±0.3)mg/g,(P<0.01);SHR组心肌细胞长径为(17.4±1.9)比(10.0±2.2)μm(P<0.01);SHR组心肌细胞短径为(9.0±2.0)比(5.8±1.7)μm(P<0.01);SHR组肥大细胞密度为(7.4±3.2)比(1.9±1.2)个/mm2(P<0.01),SHR组肥大细胞密度为WKY组的3.9倍。SHR组CVF、PVCA分别为46.4%±7.8%和1.9±0.9,WKY组分别为24.4%±10.7%和0.4±0.1,SHR组明显升高(P<0.01)。SHR组心肌Ⅰ、Ⅲ型胶原mRNA表达相对含量也均明显高于WKY(P<0.01),心脏肥大细胞密度与左室重量指数、CVF及PVCA存在明显的正相关(相关系数分别为0.67、0.87和0.95,P<0.01)。结论心脏肥大细胞密度增加可能是促进SHR心肌重构的重要原因。     

Myocyte redistribution of GRK2 and GRK5 in hypertensive,heart-failure-prone rats

Gprotein-coupled receptor kinases (GRKs) are known to be involved in the development of cardiac hypertrophy. Their exact role and subcellular distribution during cardiac hypertrophy and failure remain to be elucidated. We examined expression and subcellular distribution of GRK2 and GRK5 in the left ventricle of female spontaneously hypertensive heart failure (SHHF) rats at 6 months of age using Western blots and fluorescent confocal microscopy. GRK2 was expressed mainly in the Triton X-100 soluble fraction in the left ventricle with similar expression levels between SHHF and age-matched Wistar-Kyoto (WKY) rats. GRK2 had a striated pattern which colocalized with sarcomeric alpha-actinin and G protein in both SHHF and WKY rat myocytes and specifically accumulated in the intercalated disks of myocytes from SHHF but not WKY rats. GRK5 was expressed in both the Triton X-100 soluble fraction and Triton X-100 insoluble fraction in the left ventricle with similar expression levels between SHHF and WKY rats. GRK5 distributed diffusely in the cytoplasm in both SHHF and WKY rat myocytes and specifically accumulated in the nucleus of myocytes from SHHF but not WKY rats. GRK5 colocalized with coilin, the major component of the nuclear substructure involved in RNA synthesis and processing. The results suggest different roles for GRK2 and GRK5 in G-protein signaling and RNA biogenesis. Subcellular redistribution of GRK2 and GRK5 may be involved in cardiac hypertrophy resulting from chronic hypertension.     

Differential G protein receptor kinase 2 expression in compensated hypertrophy and heart failure after myocardial infarction in the rat

The onset of heart failure is associated with characteristic changes in myocardial expression of G protein receptor kinase 2 (GRK2). Although, GRK2 significantly contributes to the regulation of myocardial function in the failing heart, the GRK2 expression during cardiac hypertrophy without heart failure remains to be explored. We here report a differential expression of GRK2 in cardiac hypertrophy with or without heart failure in response to a myocardial infarction in the rat. Postmyocardial infarction animals were divided into two groups depending on the absence or presence of pulmonary edema, which is a manifestation of heart failure. Remarkably, cardiac GRK2 expression and activity were inhibited in animals with cardiac hypertrophy without heart failure, whereas animals with heart failure had elevated GRK2. Thus, three weeks after the infarction cardiac GRK2 expression in animals with hypertrophy alone was decreased to 0.34 of control, whereas in the group of animals with heart failure GRK2 expression was 1.89-fold higher than in sham-operated animals. GRK2 activity was affected in a similar way, three and nine weeks after the infarction cardiac GRK2 activity was reduced to 0.58 and 0.62 in animals with hypertrophy without heart failure when compared to sham operated animals. By contrast, GRK2 activity was increased by 1.32- and 1.21-fold three and nine weeks postinfarction in animals with heart failure when compared to sham animals. These data suggest that GRK2 expression is differentially regulated in hypertrophic, non-failing and hypertrophic, failing hearts. Received: 26 August 2002, Returned for 1. revision: 9 September 2002, 1. Revision received: 25 September 2002, Returned for 2. revision: 24 October 2002, 2. Revision received: 3 November 2002, Accepted: 9 November 2002 Correspondence to: S. P. Sheikh     

Hybrid transgenic mice reveal in vivo specificity of G protein-coupled receptor kinases in the heart

G protein-coupled receptor kinases (GRKs) phosphorylate activated G protein-coupled receptors, including alpha(1B)-adrenergic receptors (ARs), resulting in desensitization. In vivo analysis of GRK substrate selectivity has been limited. Therefore, we generated hybrid transgenic mice with myocardium-targeted overexpression of 1 of 3 GRKs expressed in the heart (GRK2 [commonly known as the beta-AR kinase 1], GRK3, or GRK5) with concomitant cardiac expression of a constitutively activated mutant (CAM) or wild-type alpha(1B)AR. Transgenic mice with cardiac CAMalpha(1B)AR overexpression had enhanced myocardial alpha(1)AR signaling and elevated heart-to-body weight ratios with ventricular atrial natriuretic factor expression denoting myocardial hypertrophy. Transgenic mouse hearts overexpressing only GRK2, GRK3, or GRK5 had no hypertrophy. In hybrid transgenic mice, enhanced in vivo signaling through CAMalpha(1B)ARs, as measured by myocardial diacylglycerol content, was attenuated by concomitant overexpression of GRK3 but not GRK2 or GRK5. CAMalpha(1B)AR-induced hypertrophy and ventricular atrial natriuretic factor expression were significantly attenuated with either concurrent GRK3 or GRK5 overexpression. Similar GRK selectivity was seen in hybrid transgenic mice with wild-type alpha(1B)AR overexpression concurrently with a GRK. GRK2 overexpression was without effect on any in vivo CAM or wild-type alpha(1B)AR cardiac phenotype, which is in contrast to previously reported in vitro findings. Furthermore, endogenous myocardial alpha(1)AR mitogen-activated protein kinase signaling in single-GRK transgenic mice also exhibited selectivity, as GRK3 and GRK5 desensitized in vivo alpha(1)AR mitogen-activated protein kinase responses that were unaffected by GRK2 overexpression. Thus, these results demonstrate that GRKs differentially interact with alpha(1B)ARs in vivo such that GRK3 desensitizes all alpha(1B)AR signaling, whereas GRK5 has partial effects and, most interestingly, GRK2 has no effect on in vivo alpha(1B)AR signaling in the heart.     

Pleckstrin homology domain of G protein-coupled receptor kinase-2 binds to PKC and affects the activity of PKC kinase

AIM: To study the detail mechanism of interaction between PKC and GRK2 and the effect of GRK2 on activity of PKC.METHODS: The cDNA of pleckstrin homology (PH) domain located in GRK2 residue 548 to 660 was amplified by PCR with the mRNA of human GRK2 (β1-adrenergic receptor kinase) as template isolated from human fresh placenta,the expression vector pGEX-PH inserted with the aboved cDNA sequence for GRK2 PH domain protein and the expression vectors for GST (glutathion-s-transferase) -GRK2 PH domain fusion protein, BTK (Bruton‘s tyrosine kinase)PH domain and GST protein were constructed. The expression of GRK2 in culture mammalian cells (6 cell lines:PC-3,MDCK, SGC7901, Jurkat cell etc.) was determined by SDS-PAGE and Co-immunoprecipitation. The binding of GRK2 PH domain, GST-GRK2 PH domain fusion protein and BTK PH domain to PKC in Vitro were detected by SDS-PAGE and Western blot, upon prolonged stimulation of epinephrine,the binding of GRK2 to PKC was also detected by western blot and Co-immunoprecipitation.RESULTS: The binding of GRK2 PH domain to PKC in Vitro was confirmed by western blot, as were the binding upon prolonged stimulation of epinephrine and the binding of BTK PH domain to PKC. In the present study, GRK2 PH domain was associated with PKC and down-regulated PKC activity,but Btk PH domain up-regulated PKC activity as comparedwith GRK2 PH domain.CONCLUSION: GRK2 can bind with PKC and down-regulated PKC activity.     

肿瘤抑制因子PTEN与心肌肥大关系的研究

目的 观察肿瘤抑制因子PTEN在心肌肥厚大鼠心肌组织以及在血管紧张素Ⅱ诱导的肥大心肌细胞中的表达,探讨PTEN在心肌肥大发生发展中的作用以及相关机制。方法采用腹主动脉狭窄术制备压力超负荷心肌肥厚动物模型,及血管紧张素Ⅱ诱导新生大鼠心肌细胞肥大模型,应用逆转录-聚合酶链式反应(RT-PCR)方法、Western blot及免疫组化等方法,分别检测各组PTEN mRNA和蛋白表达的变化,以及PTEN蛋白在心肌细胞中的定位。结果(1)与对照组相比,心肌肥厚组大鼠左室肌PTEN mRNA和蛋白表达均明显减少;血管紧张素Ⅱ诱导心肌细胞肥大组PTEN蛋白表达明显减少。(2)与心肌肥厚组相比,卡托普利组大鼠左室心肌PTEN mRNA和蛋白表达增加,接近对照组。(3)免疫组化实验结果显示心肌细胞胞核内有阳性免疫产物生成,提示PTEN蛋白定位于心肌细胞核内。结论PTEN在心肌肥大发生发展中可能起负调控作用,该作用与肾素-血管紧张素系统密切相关。     

Modification of cardiac subcellular remodeling due to pressure overload by captopril and losartan

In view of the activation of renin-angiotensin system under conditions associated with pressure overload on the heart, we examined the effects of captopril, an angiotensin converting enzyme inhibitor, and losartan, an angiotensin II receptor antagonist, on cardiac function, myofibrillar ATPase and sarcoplasmic reticular (SR) Ca2+-pump (SERCA2) activities, as well as myosin and SERCA2 gene expression in hypertrophied hearts. Cardiac hypertrophy was induced in rats treated with or without captopril or losartan by banding the abdominal aorta for 8 weeks; sham operated animals served as control. Decrease in left ventricular developed pressure, +dP/dt and -dP/dt as well as increase in left ventricular end diastolic pressure and increased muscle mass due to pressure overload were prevented by captopril or losartan. Treatment of animals with captopril or losartan also attenuated the pressure overload-induced depression in myofibrillar Ca2+-stimulated ATPase, myosin ATPase, SR Ca2+-uptake and SR Ca2+-release activities. An increase in beta-myosin heavy chain mRNA and a decrease in alpha-myosin heavy chain mRNA as well as depressed SERCA2 protein and SERCA2 mRNA levels were prevented by captopril or losartan. These results suggest that both captopril and losartan improve myocardial function in cardiac hypertrophy by preventing changes in gene expression and subsequent subcellular remodeling due to pressure overload.     

Modification of Cardiac Subcellular Remodeling Due to Pressure Overload by Captopril and Losartan

In view of the activation of renin-angiotensin system under conditions associated with pressure overload on the heart, we examined the effects of captopril, an angiotensin converting enzyme inhibitor, and losartan, an angiotensin II receptor antagonist, on cardiac function, myofibrillar ATPase and sarcoplasmic reticular (SR) Ca²⁺-pump (SERCA2) activities, as well as myosin and SERCA2 gene expression in hypertrophied hearts. Cardiac hypertrophy was induced in rats treated with or without captopril or losartan by banding the abdominal aorta for 8 weeks; sham operated animals served as control. Decrease in left ventricular developed pressure, +dP/dt and -dP/dt as well as increase in left ventricular end diastolic pressure and increased muscle mass due to pressure overload were prevented by captopril or losartan. Treatment of animals with captopril or Icsartan also attenuated the pressure overload-induced depression in myofibrillar Ca₂₊-stimulated ATPase, myosin ATPase, SR Ca₂₊-uptake and SR Ca²⁺-release activities. An increase in β-myosm heavy chain mRNA and a decrease in α-myosin heavy chain mRNA as well as depressed SERCA2 protein and SERCA2 mRNA levels were prevented by captopril or losartan. These results suggest that both captopril and losartan improve myocardial function in cardiac hypertrophy by preventing changes in gene expression and subsequent subcellular remodeling due to pressure overload.     

G蛋白激酶4γA142V转基因小鼠血压升高的机制探讨

目的探讨G蛋白激酶(GRK)4γ变异体A142V转基因小鼠血压升高的原因,以期了解GRK4γ在调控血压中的作用。方法以GRK4γA142V转基因小鼠为研究对象,分别对其血压、肾脏尿钠排泄功能、D1多巴胺受体的表达进行测定;并应用GRK4反义核苷酸技术处理HK-2细胞,研究在GRK4表达受到抑制的情况下D1受体的表达变化。结果与对照小鼠相比,GRK4γA142V转基因小鼠血压明显增高,肾脏D1受体介导的利尿、利钠作用明显下降,伴有肾脏皮质膜D1受体表达降低(0.6±0.2比1.5±0.2,n=3)、磷酸化程度增高[(65±7)DU比(35±7)DU,n=3];反义核苷酸抑制GRK4(1.2±0.1比1.3±0.1比0.6±0.1,n=6)表达后,D1受体的表达量增高(0.7±0.1比0.8±0.1比1.5±0.2,n=6),说明D1受体功能下降是GRK4γA142V转基因小鼠血压升高的原因。结论GRK4γ与高血压的发生关系密切,GRK4γA142V转基因小鼠血压升高与肾脏D1受体功能下降有关。