CARDIAC ANGIOTENSIN--LOAD INDUCED HYPERTROPHY & FAILURE

目的是检验心脏血管紧张素at/1的假设 与AT/2受体相反的受体激活是强制性的 与压力超负荷性肥厚的发展有关 在完好无损的心脏中过渡到失败。最近的研究表明， 牵张诱导体外培养新生大鼠心肌细胞肥大反应 依赖于局部血管紧张素II和AT/1受体的释放 激活。相反，AT/2受体的激活被认为是 拮抗AT/1介导的细胞生长。我们已经建立了一个模型 伴升主动脉带的负荷性室壁肥厚 其特征是心脏血管紧张素II活性在 早期适应性肥厚和明确的过渡后期 为失败干杯。我们发现慢性血管紧张素转换酶-- 在这个模型中，抑制可以逆转心肌细胞肥大，提高存活率， 防止收缩功能受损的发展，尽管 持续严重的左心室收缩压相对升高 到未经治疗的带状动物。这些数据暗示但不能证明 心肌AT/1受体激活在负荷性肥厚中是强制性的 以及在体内向失败的晚期过渡。在具体目标1中，我们将 测试AT/1受体激活是必需的假设，而 AT/2激活抑制负荷诱导的即刻肥大反应 原癌基因诱导和蛋白质合成，我们在 在完整的隔离灌流心脏中进行体外实验。《特定目标2》将测试 假设心脏分子对慢性压力的反应 超载和后期向失败的过渡S的特征是 心脏肾素-血管紧张素系统基因表达进行性增加 “抗生长”AT/2受体的晚期平衡上调 用定量RT-PCR方法检测。我们将利用 左心室压力超负荷发展为肥厚， 与之相邻的右室不是。特定3将测试 假设慢性AT/1受体抑制，而不是AT/2受体 抑制，逆转心肌细胞肥大，提高存活率，并修改 左心室收缩压持续升高的晚期向衰竭转变 压力相当于未经处理的带状动物。使用现在经过验证的 方法学，我们将在活体内使用连续的 超声心动图和左心室微压计压力测量。特定的 4将决定收缩功能改善的细胞基础 在慢性AT/1受体抑制中的作用。基于初步的 应用荧光指示剂对游离肥大心肌细胞的研究 和钙调节基因表达的测量，我们预测 心肌细胞[Ca~(2+)]/i和pH/I调节的改善 钙离子调节基因表达的正常化水平。这些集成在一起 体内生理学、分离的心肌细胞和心脏基因的研究 表达，将决定心脏AT/1受体激活是否 对于负荷诱导的即刻肥大反应是强制性的，晚期 体内从肥大到衰竭的转变。这些问题是 是人类肥大和失败的生物学基础。

The objective is to test the hypothesis that cardiac angiotensin At/1 receptor activation, which is opposed by the AT/2 receptor, is mandatory for the development of pressure overload hypertrophy and the later transition to failure in the intact heart. Recent studies show that the stretch-induced hypertrophic response of neonatal myocytes in vitro depends on the local release of angiotensin II and AT/1 receptor activation. In contrast, AT/2 receptor activation is postulated to counteract AT/1-mediated cell growth. We have established a model of load-induced ventricular hypertrophy with ascending aortic banding which is characterized by increased cardiac angiotensin II activation during early adaptive hypertrophy, and a well-defined later stage of transition to failure. We have made the novel observation that chronic ACE- inhibition in this model regresses myocyte hypertrophy, improves survival, and prevents the development of impaired contractile function despite persistent severe elevation of left ventricular systolic pressure relative to untreated banded animals. These data implicate but do not prove that cardiac AT/1 receptor activation is mandatory for load-induced hypertrophy and the late transition to failure in vivo. In Specific Aim 1 we will test the hypothesis that AT/1 receptor activation is required, whereas AT/2 activation inhibits, the load-induced immediate hypertrophic response of protooncogene induction and protein synthesis that we have shown in vitro in the intact isolated perfused heart. Specific Aim 2 will test the hypothesis that the cardiac molecular response to chronic pressure overload and the late transition to failure s characterized by the progressive increased expression of cardiac renin-angiotensin system genes with late counterbalancing upregulation of the "anti-growth" AT/2 receptor as measured by quantitative RT-PCR. We will exploit comparison of the pressure overloaded left ventricle which develops hypertrophy, and the adjacent right ventricle which does not. Specific 3 will test the hypothesis that chronic AT/1 receptor inhibition, but not AT/2 receptor inhibition, regresses myocyte hypertrophy, improves survival, and modifies the late transition to failure with persistent elevation of LV systolic pressure equivalent to untreated banded animals. Using now validated methodology, we will quantitate cardiac function in vivo using serial echocardiography, and LV micromanometer pressure measurements. Specific 4 will determine the cellular basis of the improvement in contractile function in chronic AT/1 receptor inhibition. Based on preliminary studies in dissociated hypertrophied myocytes using fluorescent indicators and measurements of calcium regulatory gene expression, we predict an improvement in myocyte [Ca2+]/i and pH/i regulation in association with normalized levels of Ca2+ regulatory gene expression. These integrated studies of in vivo physiology, the isolated myocyte, and cardiac gene expression, will determine if cardiac AT/1 receptor activation is mandatory for load-induced immediate hypertrophic response, and the late transition from hypertrophy to failure in vivo. These questions are fundamental to the biology of human hypertrophy and failure.