卡托普利对高血压左心室肥大心肌细胞中GRK_2表达和亚细胞分布的影响

目的:研究G蛋白偶联受体激酶2(GRK2)在高血压心肌肥大发生发展机制中的作用和卡托普利对心肌中GRK2表达水平、活性及亚细胞分布的影响,探讨卡托普利抑制心肌肥大的机制.方法:通过免疫荧光标记、共聚焦显微镜及Western blot等方法,检测6月龄的WKY(WKY组)、自发性高血压(SHR,SHRA组)大鼠,8月龄SHR(SHRB组)和卡托普利干预SHR(SHRC组)大鼠左心室心肌细胞中GRK2的表达及其分布.结果:各组大鼠左室心肌组织总蛋白中GRK2表达无明显变化(P>0.05).细胞质中GRK2表达SHRA组比WKY组表达减少(P<0.01);SHRB组比SHRC组GRK2表达进一步减少(P<0.01);而SHRC组比SHRB组GRK2表达增加( P<0.05).细胞膜蛋白中GRK2在SHRA组比WKY组表达增加(P<0.01);SHRB组比SHRA组GRK2表达进一步增加(P<0.05);而SHRC组比SHRB组GRK2表达减少(P<0.01).细胞核蛋白中无GRK2表达.共聚焦显微镜观察发现GRK2在SHR大鼠细胞膜特别是心肌细胞两端的闰盘聚集明显,卡托普利能减少GRK2在细胞膜分布.结论:GRK2与心肌细胞肥大发生发展关系密切,参与心肌肥大细胞信号转导的调控,卡托普利能通过调节GRK2亚细胞分布而发挥抑制心肌肥大作用.     

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     

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。     

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.     

长期芦沙坦治疗对自发性高血压大鼠心肌间质的影响

目的:确定长期芦沙坦治疗能否逆转自发性高血压大鼠(SHR)心肌纤维化.方法:本实验选用33周龄Wistar-Kyoto(WKY)大鼠8只,SHR未用药组6只,SHR用药组6只(已口服17周芦沙坦30 mg/kg/d).大鼠断头处死,取出心脏标本进行检测.血压、心脏重量、左心室重量、左心室重量指数测定用常规方法.纤维胶原用左心室心肌组织切片行VanGieson染色,图象用真彩色图象分析系统计算左室胶原容积分数,进行定量评估.免疫组化染色左心室心肌组织切片Ⅲ型胶原,用记分法进行半定量分析.电镜观察左心室心肌间质形态学变化.用3×1000放大比例计算每个视野成纤维细胞数,每个标本随机取10个视野,比较各组间成纤维细胞数的差异.结果:与WKY组大鼠相比较,SHR存在高血压、心肌肥大、左心室胶原容积分数增加.免疫组化分析左心室Ⅲ型胶原增加,电镜观察成纤维细胞数增加,有统计学显著性差异.与SHR组相比,SHR用药组高血压、左心室重量、左心室胶原容积分数降低.免疫组化分析左心室Ⅲ型胶原减少.但成纤维细胞数无明显变化.结论:芦沙坦在逆转自发性高血压大鼠心肌肥大,同时能减少基质胶原沉积.但电镜形态学观察,不能抑制成纤维细胞增殖.     

长期芦沙坦治疗对自发性高血压大鼠心肌间质的影响

目的 :确定长期芦沙坦治疗能否逆转自发性高血压大鼠(SHR)心肌纤维化。方法 :本实验选用 33周龄Wistar Kyoto(WKY)大鼠 8只 ,SHR未用药组 6只 ,SHR用药组 6只 (已口服 17周芦沙坦 30mg/kg/d)。大鼠断头处死 ,取出心脏标本进行检测。血压、心脏重量、左心室重量、左心室重量指数测定用常规方法。纤维胶原用左心室心肌组织切片行VanGieson染色 ,图象用真彩色图象分析系统计算左室胶原容积分数 ,进行定量评估。免疫组化染色左心室心肌组织切片Ⅲ型胶原 ,用记分法进行半定量分析。电镜观察左心室心肌间质形态学变化。用 3× 10 0 0放大比例计算每个视野成纤维细胞数 ,每个标本随机取 10个视野 ,比较各组间成纤维细胞数的差异。结果 :与WKY组大鼠相比较 ,SHR存在高血压、心肌肥大、左心室胶原容积分数增加。免疫组化分析左心室Ⅲ型胶原增加 ,电镜观察成纤维细胞数增加 ,有统计学显著性差异。与SHR组相比 ,SHR用药组高血压、左心室重量、左心室胶原容积分数降低。免疫组化分析左心室Ⅲ型胶原减少。但成纤维细胞数无明显变化。结论 :芦沙坦在逆转自发性高血压大鼠心肌肥大 ,同时能减少基质胶原沉积。但电镜形态学观察 ,不能抑制成纤维细胞增殖。     

自发性高血压大鼠左室重构中细胞增殖及心肌细胞DNA倍体的变化

目的 :探讨组织细胞增殖在高血压左室重构中的变化规律。方法 :不同年龄 (1周、3、6、12月龄 )的 WKY和 SHR大鼠 ,称重法测量左室肥厚指数 ,L SAB免疫组化法检测左室中增殖细胞核抗原 (PCNA)的蛋白表达 ,图像细胞分析技术原位检测心肌细胞核 DNA倍体和细胞核面积的变化。结果 :1周、3、6、12月龄各组 SHR左室肥厚指数分别比同龄WKY增加 18%、15 %、2 6 %、2 6 % ,均有统计意义。 1周龄和 3月龄 SHR心肌细胞 PCNA阳性率较同龄 WKY显著增加 ;而纤维细胞阳性率在两株大鼠无明显差异。 6月龄 WKY无阳性细胞表达 ,SHR心肌细胞阳性率为 0 .13± 0 .0 7,无统计学意义。 12月龄 WKY和 SHR均无阳性细胞表达。各年龄段SHR4倍体心肌细胞核百分比和心肌细胞核面积均较 WKY大鼠显著增加。在 1周至 12月龄时 ,两株大鼠 4倍体心肌细胞核比例均随年龄呈线性生长 ,6月龄后 WKY倍体比例相对稳定 ,SHR增加幅度明显下降。回归分析表明 ,成年 SHR4倍体比例与动脉收缩压呈相正关性。结论 :SHR左室重构在新生鼠即已发生 ,在 6月龄时基本完成 ,并且不完全依赖于血压的增高。这种病理性变化表现为心肌细胞的增殖 (肥大和 /或增生 ) ,而纤维细胞无明显增殖     

血管紧张素转换酶抑制剂对自发性高血压大鼠肥大和衰竭心肌的纤维化及其功能的影响

目的 雄性自发性高血压大鼠(SHR)心肌经过一段时间的稳定肥大后,在18至24月龄时发生心力衰竭。我们的研究目的是观察在雄性SHR,ACEI开始治疗的时间与预防或逆转心肌纤维化及心肌功能障碍的关系。 方法和结果 雄性SHR和正常血压的大鼠(WKY)分为未经治疗组或卡托普利治疗组(2g/L在饮用水中),治疗开始于12、18,21月龄;在24月龄时进行研究,或在SHR出现明显的心力衰竭时开始研究,平均(19±2)月龄。在另外一组,卡托普利组治疗开始于     

自发性高血压大鼠左室重构中细胞增殖及心肌细胞DNA倍体的变化

目的:探讨组织细胞增殖在高血压左室重构中的变化规律.方法:不同年龄(1周、3、6、12月龄)的WKY和SHR大鼠,称重法测量左室肥厚指数,LSAB免疫组化法检测左室中增殖细胞核抗原(PCNA)的蛋白表达,图像细胞分析技术原位检测心肌细胞核DNA倍体和细胞核面积的变化.结果:1周、3、6、12月龄各组SHR左室肥厚指数分别比同龄WKY增加18%、15%、26%、26%,均有统计意义.1周龄和3月龄SHR心肌细胞PCNA阳性率较同龄WKY显著增加;而纤维细胞阳性率在两株大鼠无明显差异.6月龄WKY无阳性细胞表达,SHR心肌细胞阳性率为0.13±0.07,无统计学意义.12月龄WKY和SHR均无阳性细胞表达.各年龄段SHR 4倍体心肌细胞核百分比和心肌细胞核面积均较WKY大鼠显著增加.在1周至12月龄时,两株大鼠4倍体心肌细胞核比例均随年龄呈线性生长,6月龄后WKY倍体比例相对稳定,SHR增加幅度明显下降.回归分析表明,成年SHR 4倍体比例与动脉收缩压呈相正关性.结论:SHR左室重构在新生鼠即已发生,在6月龄时基本完成,并且不完全依赖于血压的增高.这种病理性变化表现为心肌细胞的增殖(肥大和/或增生),而纤维细胞无明显增殖.     

伊贝沙坦逆转高血压左心室肥厚的细胞学机制

目的探讨伊贝沙坦(IBT)抗高血压左心室肥厚过程中,对心肌细胞凋亡和心肌肌浆网钙泵活性的影响。方法选用16周龄自发性高血压大鼠(SHR)24只,随机分为IBT组(8只)、蒸馏水(DW)组(8只)和SHR0组(8只),另选16只WKY大鼠作为正常对照,随机分为WKY0组(8只)和WKY1组(8只)。IBT组大鼠给予IBT(60 mg.kg-1.d-1)加适量蒸馏水灌胃14周。治疗前后,测量血压和左心室心肌肥厚指数(LVMI),原位末端脱氧核糖核苷酸转移酶介导的dUTP缺口末端标记法检测心肌细胞凋亡,并检测治疗后左心室心肌细胞肌浆网Ca2+-ATP酶活性。结果DW组LVMI、心肌细胞凋亡指数均显著高于WKY组,而IBT组明显低于DW组;DW组Ca2+-ATP酶活性明显低于IBT组及同龄WKY组,IBT组稍低于同龄WKY组;Ca2+-ATP酶活性与LVMI、心肌细胞凋亡指数呈显著负相关,LV-MI与心肌细胞凋亡指数呈显著正相关。结论IBT可能通过调节心肌细胞肌浆网钙泵活性以抑制高血压左心室肥厚过程中心肌细胞凋亡,从而逆转左心室肥厚。     

厄贝沙坦和咪达普利抑制自发性高血压大鼠左心室重塑的研究

目的:探讨咪达普利、厄贝沙坦对自发性高血压大鼠(SHR)左心室重塑的抑制作用,并比较二者的作用效果。方法:选用13周龄的SHR30只、Wistar-Kyoto(WKY)大鼠10只,随机分为4组:SHR组,厄贝沙坦组,咪达普利组,WKY组。实验期15周。观察血压、左室重量/体重(LVW/BW)、左室厚度/BW,心肌的形态学(光镜、电镜),血浆、心肌血管紧张素Ⅱ(AngⅡ)及心钠素(ANF)浓度。结果:与SHR组相比,咪达普利组、厄贝沙坦组血压控制良好,LVW/BW、左室厚度/BW均比SHR组小(均P<0.05),血浆、心肌的ANF水平均比SHR组低(均P<0.001),咪达普利组血浆AngⅡ水平低于SHR组,但差异无统计学意义,心肌AngⅡ水平低于SHR组(P<0.05),厄贝沙坦组血浆、心肌AngⅡ水平均明显高于SHR组(均P<0.001),两组心肌结构改变尤其是纤维化均比SHR组减轻,咪达普利组减轻更明显。结论:咪达普利、厄贝沙坦不仅能良好地控制血压,而且可以抑制SHR左心室重塑;在防止心肌和肠系膜动脉结构改变尤其是纤维化方面,咪达普利作用可能优于厄贝沙坦。     

Isoproterenol sensitivity of isolated cardiac myocytes from rats with monocrotaline-induced right-sided hypertrophy and heart failure

Rats treated with the alkaloid monocrotaline developed right ventricular hypertrophy with a left:right ventricle weight ratio of 1.35 +/- 0.10 (mean +/- s.e.m., n = 25) compared with 3.83 +/- 0.40 (n = 14) in diet-matched controls (P less than 0.001). Urine volume and sodium content were reduced and body water increased consistent with heart failure. In 10 out of 26 treated rats pleural, pericardial or peritoneal effusions were present. Urine norepinephrine content was significantly raised (P less than 0.02) but epinephrine was unchanged. Plasma norepinephrine levels were raised though not significantly. Myocytes isolated from the right ventricle had a reduced myosin Ca2+-activated ATPase (P less than 0.05) activity and a shift towards slower V2 and V3 myosin isoforms. There was no decrease in maximum contraction amplitude with calcium or isoproterenol in either left or right ventricular cells of treated rats. Right ventricular cells from treated rats showed a reduced rate of contraction in maximum isoproterenol (P less than 0.05) and a significant rightward shift in PD2 (P less than 0.05) representing a two-fold increase in EC50 for isoproterenol compared with right ventricular cells from control animals. There was no shift in EC50 for isoproterenol in left ventricle cells. In parallel experiments, myocytes isolated from both ventricles of rats treated with isoproterenol for one week showed a rightward shift of more than 50-fold in the isoproterenol concentration-response curve and a depressed response to maximum isoproterenol. In the rat monocrotaline model of right-sided cardiac hypertrophy and failure, changes in sensitivity to beta-adrenoceptor agonists are slight, and present only in the right ventricle. The lack of change in the left ventricle seems to suggest that this functional desensitisation is not a consequence of raised circulating catecholamines.     

Assessment of the nitric oxide system in the heart, aorta and kidney of aged Wistar-Kyoto and spontaneously hypertensive rats

OBJECTIVE: To assess the nitric oxide (NO) system in the cardiovascular and renal systems of old Wistar-Kyoto (WKY) rats and old spontaneously hypertensive rats (SHR) compared with young rats of the same strains. DESIGN AND METHODS: The NO pathway was assessed: (i) in analytical studies measuring the concentration of nitrate in plasma and the activity of NO synthases in the left ventricle, renal cortex and renal medulla; and (ii) in functional studies, in which we measured the blood pressure effects of NO blockade with intravenous N-nitro-L-arginine methyl ester (L-NAME, 0.1 mg/kg) in anaesthetized rats. In addition, we studied NO production in the aorta comparing the force attained by isolated segments exposed to cumulative concentrations of L-NAME (10(-7)-10(-3) mol/l). RESULTS: Plasma nitrate was significantly higher in old rats of both strains. Calcium-dependent NO synthase activity was markedly upregulated in the left ventricle, renal cortex and renal medulla of the old rats, both in hypertensive and normotensive animals. Intravenous L-NAME elicited deeper pressor effects in the old rats of either blood pressure condition. Aortic segments from old WKY rats, but not those from SHR, achieved remarkably stronger tension in response to L-NAME compared with the young counterparts. CONCLUSIONS: These findings suggest that the NO system is upregulated in the cardiovascular system and the kidney in senescence, even in hypertension.     

Regulation of expression of M, B, and mitochondrial creatine kinase mRNAs in the left ventricle after pressure overload in rats

Pressure overload of the left ventricle induces synthesis of creatine kinase isoenzymes. To determine whether this response is associated with an altered pattern of creatine kinase gene expression, we induced arterial hypertension in rats by suprarenal aortic banding. After 4 days, left ventricular myocardium from hypertensive (n = 7) and normotensive, sham-operated (n = 5) rats was analyzed for isoenzyme activities by chromatography; M and B creatine kinase subunit protein by Western blot; and M, B, and mitochondrial creatine kinase mRNA by Northern blot. Although total creatine kinase activity increased in hypertensive (1,096 +/- 214 IU/g left ventricle) compared with normotensive rats (648 +/- 81 IU/g left ventricle, p less than 0.01), the relative proportions of the cytoplasmic and mitochondrial isoenzymes did not change. The mass of M and B subunits increased 1.9- and 2.7-fold, respectively, in hypertensive compared with control rats. Similarly, the mRNA for M and B subunits as well as mitochondrial creatine kinase increased 2.6-, 1.6-, and 1.8-fold, respectively, in hypertensive rats compared with control rats. Thus, increased energy requirements in acute pressure overload are met by generalized induction of creatine kinase mRNA and subunit protein and not by an isoenzyme switch.     

High rate of right ventricular infarction after ligation of mid left anterior descending artery in rats

BACKGROUND: The left anterior descending artery (LAD) supplies the left ventricle in humans. LAD ligation has been commonly used in rats to induce left ventricular (LV) infarction for research purposes. However, the myocardial supply territories of LAD are not well established in rats. We measured the infarction zone in rats after ligation of the mid-LAD. METHODS: Twenty-four male Sprague-Dawley rats weighing 300-350 g were selected for LAD ligation for the induction of ischemic cardiomyopathy. The surgery was performed under full anesthesia. Left-sided thoracotomy was performed through cuts in the fifth and sixth ribs. Ligation of the LAD was performed 1 to 2 mm distal to a line between the left border of the pulmonary conus and the right border of the left atrial appendage. LAD was ligated after the first diagonal and septal branches. After 24 h, the hearts were removed and stained with Tetrazolium Tetrachloride (TTC) for the detection of infracted areas. RESULTS: Ligation of LAD induces 85% infarction of the right anterior free wall and anterior right ventricular septum and induces 100% infarction of the anterior free wall of the left ventricle and anterior septum. Infarction after LAD ligation extends all the way to the distal of the ligation site down to the apex of the heart. CONCLUSIONS: Mid-LAD ligation after the first septal and diagonal branches causes substantial right ventricular infarction in addition to LV infarct in rats. Therefore, the hemodynamic effect of right ventricle infarct should be considered in research involving LAD ligation in rats.     

厄贝沙坦和咪哒普利对自发性高血压大鼠左室肥厚和c-Jun表达的影响

目的探讨厄贝沙坦和咪哒普利对自发性高血压大鼠（SHR）左室肥厚和c-Jun表达的影响。方法选用13周龄的SHR 30只,雌性9只,雄性21只,体质量（229±39）g,随机分为3组:SHR组,厄贝沙坦组,咪哒普利组,每组雌性3只,雄性7只。另选同源同系、血压正常的Wistar-Kyoto大鼠（WKY）10只,雌性5只,雄性5只,体质量（206±49）g,作为正常对照组（WKY组）。实验期14周。观察指标:血压、左室质量/体质量（LVW/BW）、左室厚度/体质量、左心室肌c-Jun蛋白及mRNA水平。结果26周龄SHR组血压、LVW/BW与左室厚度/体质量均增高,左心室肌c-Jun蛋白和mRNA的表达明显增加;咪哒普利组、厄贝沙坦组血压、LVW/BW、左室厚度/体质量、左心室肌c-Jun蛋白和mRNA的表达均降低。结论自发性高血压可明显导致心肌肥厚,而咪哒普利、厄贝沙坦可明显降低血压、抑制心肌肥厚的发生。     

Doxazosin modifies Bcl-2 and Bax protein expression in the left ventricle of spontaneously hypertensive rats

BACKGROUND: Increased apoptosis has recently been reported in the heart of spontaneously hypertensive rats (SHRs). OBJECTIVE: To investigate the molecular basis of apoptosis in the left ventricle of SHRs in terms of the expression of Bcl-2 protein (which protects from apoptosis) and Bax protein (which acts as an apoptotic promoter). In addition, we analysed the involvement of alpha -adrenergic receptors in the left ventricular apoptosis of SHRs. METHODS: The study was performed in untreated SHRs (n=16) and SHRs that were orally treated with doxazosin (10 mg/kg body weight per day, for 15 days), a selective alpha1-receptor blocker (n=16). A group of Wistar-Kyoto (WKY) rats (n=16) was used as the control. RESULTS: The left ventricles of untreated SHRs showed a significant increase in Bcl-2 protein expression and a reduced presence of Bax protein. The ratio of Bcl-2:Bax in SHRs was higher than in WKY rats, suggesting an anti-apoptotic state. Paradoxically, both the number of apoptotic cardiac cells and the cleavage of an 85-kDa fragment of the poly (ADP-ribose) polymerase (PARP), a marker of caspase-3 activity, were higher in the left ventricle of SHRs than in WKY rats, suggesting an apoptotic situation. Bax promotes cell apoptosis when it is bound to Bcl-2. We then determined the abundance of Bax-Bcl-2 complexes in the left ventricle of the two groups of animals. Bax-Bcl-2 complexes were more abundant in SHRs than WKY rats. In a second set of experiments, we analysed the role of alpha1-adrenergic blockade by doxazosin in the above-described mechanisms. Doxazosin treatment reduced the formation of Bax-Bcl-2 complexes in the left ventricle of SHRs, and this was accompanied by a decrease in the levels of 85kDa PARP and a reduction in apoptotic left ventricular cells. CONCLUSIONS: The present work suggests that the presence of Bax-Bcl-2 complexes in the left ventricle could be a more reliable marker of the apoptotic state than the determination of the absolute expression of Bcl-2 and Bax proteins. Moreover, the inhibition of alpha1 -adrenergic receptors by doxazosin decreased the abundance of BaxBcl-2 complexes and promoted a reduction of apoptosis in the left ventricle of SHRs.     

Differential effects of cardiac hypertrophy and failure on right versus left ventricular calcium activation

We studied calcium responsiveness of skinned muscle preparations from the right and left ventricles of rats with cardiac hypertrophy and cardiac hypertrophy plus failure. To test the hypothesis that differences in contractile function are due to changes in myofilament calcium responsiveness, we compared preparations from spontaneously hypertensive rats with cardiac failure, spontaneously hypertensive rats without cardiac failure, and age-matched normotensive Wistar-Kyoto control rats 18-24 months of age. Rats with failure had pleural/pericardial effusions, left atrial thrombi, and right and left ventricular hypertrophy. Muscles were skinned by saponin (250 micrograms/ml) and activated with a series of calcium buffers. Data were plotted as pCa (-log[Ca2+]) versus isometric force and then fit to a modified Hill equation. Values for 50% maximal activation (calcium sensitivity), maximal calcium-activated force, and the slope of the calcium-force relation were compared. Our data indicate that with the development of hypertrophy, calcium sensitivity of left ventricular muscles remains unaffected, but maximal calcium-activated force is increased. In contrast, maximal calcium-activated force declines toward control levels with the development of left ventricular failure, despite the continued presence of significant hypertrophy. In the normotensive rats, the left ventricle is more sensitive to calcium than the right ventricle (pCa50 = 6.0 +/- 0.05 versus 5.7 +/- 0.09; p less than 0.05); however, both the calcium sensitivity and maximal calcium-activated force of the right ventricle increase with the development of compensatory hypertrophy secondary to left ventricular failure. These changes that occur in rats with cardiac hypertrophy and failure may represent important physiological adaptive mechanisms.     

Biventricular repair in neonates with hypoplasia of the left ventricle]

BACKGROUND: Whether to perform uni or biventricular repair in ducto dependent neonates with hypoplastic but morphologically normal left ventricle and multi level left ventricle obstructions (hypoplastic left heart syndrome class III) remains unanswered. Echocardiographic criteria have been proposed for surgical decision. HYPOTHESIS: Increased afterload and multi level left ventricle obstruction is constant. We assumed that restoration of normal loading conditions by relief of left ventricle obstructions promotes its growth, provided that part of the cardiac output was pre operatively supported by the left ventricle, whatever the echocardiographic indices. METHODS: Twenty one ducto dependent neonates presented with this anomaly. All had aortic coarctation associated to multi level left ventricle obstruction. Pre operative echocardiographic assessment showed: mean end diastolic left ventricular volume of 13.3 +/- 3.5 mL/m2 and mean Rhodes score of -1.43 +/- 0.9. Surgery consisted in relief of left ventricle outflow tract obstruction by coarctation repair in 21 associated to atrial septal defect closure in 2, aortic commissurotomy in 1 and ascending aorta enlargement in 1. RESULTS: There were 3 early and 3 late deaths. There was no predictive risk factor for failure. Growth of the left heart was demonstrated in most patients. At hospital discharge the end diastolic left ventricular volume was 19.4 +/- 3.12 mL/m2 (p = 0.0001) and the Rhodes score was -0.38 +/- 1.01 (p = 0.0003). Actuarial survival and freedom from reoperation rates at 5 years were: 68.5% and 40.75%, respectively. CONCLUSION: Biventricular repair can be proposed to ducto dependent neonates with hypoplastic but morphologically normal left ventricle provided that all anatomical causes of left ventricle obstruction can be relieved. Secondary growth of the left heart then occurs, however the reoperation rate is not low.     

Analysis of circadian blood pressure rhythm and target-organ damage in stroke-prone spontaneously hypertensive rats

OBJECTIVE: We compared diurnal patterns of blood pressure in Wistar-Kyoto (WKY) rats, spontaneously hypertensive rats (SHR) and stroke-prone spontaneously hypertensive rats (SHRSP), and analyzed the relationship between the change in diurnal patterns of blood pressure and target-organ damage in SHRSP. MATERIALS AND METHODS: Blood pressure, heart rate and motor activity in the three groups of rats were continuously monitored by radiotelemetry, from 1100 h on the first measuring day to 1300 h on the third measuring day. The left ventricular weight and the ratio of beta-myosin heavy chain to alpha-myosin heavy chain in the cardiac left ventricle, morphological changes in the glomerular basement membrane in the kidney, 24 h urinary protein excretion and brain weights were also measured in 10-, 12- or 17-week-old SHRSP. RESULTS: The SHR circadian blood pressure rhythm exhibited a pattern which peaked during the rats' active (light-off or dark) phase, but the peak time was a little closer to the resting (light-on) phase compared with that for WKY rats. Although the circadian blood pressure rhythm for 10-week-old SHRSP was similar to that observed for SHR, the patterns in 12- and 17-week-old SHRSP were shifted further towards the resting phase. Heart and left ventricular weight increased with the progression of hypertension. The ratio of beta- to alpha-myosin heavy chain in the left ventricle was higher in 12- and 17-week-old SHRSP than in 10-week-old SHRSP. Brain weight was increased significantly in 17-week-old SHRSP compared with 10- and 12-week-old SHRSP. Increased urinary protein excretion and morphological changes in the glomerular basement membrane in the kidney were observed in 12- and 17-week-old SHRSP. CONCLUSIONS: These data suggest that SHRSP have an abnormal circadian blood pressure rhythm associated with hypertensive target-organ damage. This rat strain may therefore be a useful model in which to investigate the mechanisms responsible for the alteration in the circadian blood pressure rhythm, and to analyze the relationship between the abnormal circadian rhythm and target-organ damage.