AGING AND CARDIOCYTE MITOCHONDRIAL CA++ HANDLING IN SITU

到了老年，心脏的功能会减弱， 心脏对缺血损伤的易感性增加。年龄- 心肌钙调节的依赖性改变已被牵连 作为这两种功能观察的细胞基础。那里 现在有证据表明抑制心脏疾病的药物 线粒体Ca~(2+)超载可显著减轻心肌损伤 缺血发作后的损伤。我们的实验室最近获得了 与以下观点相一致的初步证据 完整左室心肌细胞线粒体的渐进性老化 当肌浆钙时有更大的摄取钙的倾向 浓度升高了。这种依赖于年龄的适应可能是 被认为是阳性的，就线粒体钙的增加而言 摄取率/容量可能代表了一种细胞机制来补偿 对于众所周知的与年龄相关的肌浆钙清除减少 肌浆网(SR)。然而，这种适应方式， 可能还会增加线粒体钙超载的风险， 尤其是在挑战心肌钙离子处理的条件下 系统。该试点项目的主要目标是确定 增龄对线粒体钙摄取的影响 完好率左室心肌细胞的特征。我们建议研究 成年(8个月)F344xBN大鼠成熟心肌细胞的分离 成年期(16个月)，晚年(32个月)。荧光 显微镜(Fura-2)将被用来评估肌浆[钙]动力学 和快速解决方案切换技术将用于隔离和 消除SR和NACA交换(NaCaX)介导的钙去除 机械装置。确定线粒体对非SR的贡献 和非NaCaX介导的肌浆钙去除，我们将使用 Ru红(25 NM)抑制线粒体钙摄取和 二氢化氢-2AM测定线粒体[Ca2+]。我们的初步数据 清楚地表明，非SR和非NaCaX介导的能力 肌浆钙清除量在高龄时增加。如果这个 反映线粒体钙摄取增加，然后强烈 可以这样说，高龄会引起 线粒体钙处理。这可能会对 关于我们对年龄相关性损失的细胞基础的理解 心肌对缺血损伤的抵抗及其调节 老年心脏的氧化代谢。

In advanced age, the performance of the heart is diminished and the susceptibility of the heart to ischemic injury is increased. Age- dependent alterations in myocardial Ca2+ regulation have been implicated as the cellular basis for both of these functional observations. There is now evidence indicating that agents that inhibit cardiac mitochondrial Ca2+ overload can significantly spare the myocardium from injury following bouts of ischemia. Our laboratory recently acquired preliminary evidence that are consistent with the idea that with progressive aging, mitochondrial in intact left ventricular cardiocytes have a greater propensity to take up Ca2+ when sarcoplasmic Ca2+ concentration is elevated. Such an age-dependent adaptation could be viewed as being positive insofar as an increase in mitochondrial Ca2+ uptake rate/capacity may represent a cellular mechanism to compensate for the well-known age-related diminution in sarcoplasmic Ca2+ clearance by the sarcoplasmic reticulum (SR). This type of adaptation, however, might also increase the risk of mitochondrial Ca2+ overload, particularly under conditions that challenge myocardial Ca2+ handling systems. The primary objective of this pilot project is to determine the effect of progressive age on mitochondrial Ca2+ uptake characteristics in intact rate LV cardiocytes. We propose to study myocytes isolated from F344xBN rats in young adulthood (8 mos), mature adulthood (16 mos), and in advanced age (32 mos). Fluorescence microscopy (fura-2) will be used to assess sarcoplasmic [Ca2+] dynamics and rapid solution switching techniques will be used to isolate and eliminate both SR and NaCa exchange (NaCaX) mediated Ca2+ removal mechanisms. To determine the contribution of the mitochondria to nonSR and nonNaCaX mediated Ca2+ removal from the sarcoplasm, we will use ruthenium red (25 nM) to suppress mitochondrial Ca2+ uptake and dihydrorhod-2AM to assess mitochondrial [Ca2+]. Our preliminary data clearly indicate that the capacity of nonSR-and nonNaCaX-mediated sarcoplasmic Ca2+ clearance increases in advanced age. If this reflective of an increase in mitochondrial Ca2+ uptake, then a strong case could be made that advanced age elicits intrinsic changes in mitochondrial Ca2+ handling. This may have profound implications with regard to our understanding of the cellular basis age-related losses in myocardial resistance to ischemic damage and to the regulation of oxidative metabolism in the aged heart.