Assayag P, CHarlemagne D, Marty I, de Leiris J, Lompré A M, Boucher F, Valére P E, Lortet S, Swynghedauw B, Besse S
Groupe de Physiophathologie Cellulaire Cardiaque, ESA CNRS 5077, Université Joseph Fourier, Grenoble, France.
Cardiovasc Res. 1998 Apr;38(1):169-80. doi: 10.1016/s0008-6363(97)00283-6.
Both aging and myocardial ischemia are associated with alterations of calcium-regulating proteins. We investigated the effects of graded levels of low-flow ischemia on myocardial function and on SR Ca(2+)-ATPase (SERCA2), Na(+)-Ca2+ exchanger (NCX) and ryanodine receptor (RyR2), at mRNA and protein levels in both adult and senescent myocardium.
Isolated hearts from 4 and 24 month old (mo) rats were retrogradely perfused during 180 min at 100% (100% CF, n = 11 and n = 11 respectively. 30% (30% CF, n = 10 and n = 12) or 15% (15% CF, n = 13 and n = 8) of their initial coronary flow, and active tension and coronary resistance (in % of their baseline value) were recorded. After 180 min of perfusion. NCX, RyR2 and SERCA2 mRNAs (in % of age-matched 100% CF group value) and protein levels were quantitated in the left ventricles by slot blot and Western blot analysis, respectively.
In 24 mo hearts, low-flow ischemia induced a greater fall in active tension (-65 +/- 7% vs. -40 +/- 4% in 4 mo 30% CF, p, 0.01 and -82 +/- 2% vs. -60 +/- 5% in 4 mo 15% CF groups, p < 0.05 after 15 min of ischemia) and a greater increase in coronary resistance (+357 +/- 44% vs. +196 +/- 39% in 4 mo 30% CF, p < 0.05 and +807 +/- 158% vs. +292 +/- 61% in 4 mo 15% CF groups, p < 0.001 after 15 min of ischemia). An increased accumulation of SERCA2 (+36% and NCX (+46%) transcripts, but not RyR2, already occurred in 24 mo 30% CF group while the 3 transcripts accumulated in 24 mo 15% CF group. In 4 mo rats SERCA2 (+26%), NCX (+35%) and RyR2 (+81%) mRNA levels only increased in the 15% CF group. Corresponding calcium-regulating protein levels were unaltered whatever the degree of flow reduction in both 4 mo and 24 mo hearts.
Low-flow ischemia does not induce calcium-regulating protein loss in both adult and senescent hearts. The increase in mRNAs coding for calcium-handling proteins and the impairment of myocardial function which occur at a lesser degree of coronary flow reduction in senescent hearts, indicate a higher vulnerability to low-flow ischemia during aging.
衰老和心肌缺血均与钙调节蛋白的改变有关。我们研究了不同程度的低流量缺血对成年和衰老心肌的心肌功能以及肌浆网Ca(2+)-ATP酶（SERCA2）、钠钙交换体（NCX）和兰尼碱受体（RyR2）在mRNA和蛋白质水平的影响。
分别从4月龄和24月龄大鼠分离心脏，以初始冠脉流量的100%（100%CF，分别为n = 11和n = 11）、30%（30%CF，n = 10和n = 12）或15%（15%CF，n = 13和n = 8）进行逆行灌注180分钟，并记录主动张力和冠脉阻力（相对于基线值的百分比）。灌注180分钟后，通过狭缝印迹法和蛋白质印迹分析分别对左心室中的NCX、RyR2和SERCA2 mRNA（相对于年龄匹配的100%CF组值的百分比）和蛋白质水平进行定量。
在24月龄心脏中，低流量缺血导致主动张力下降幅度更大（缺血15分钟后，24月龄30%CF组为-65±7%，4月龄30%CF组为-40±4%，p < 0.01；24月龄15%CF组为-82±2%，4月龄15%CF组为-60±5%，p < 0.05），冠脉阻力增加幅度更大（缺血15分钟后，24月龄30%CF组为+357±44%，4月龄30%CF组为+196±39%，p < 0.05；24月龄15%CF组为+807±158%，4月龄15%CF组为+292±61%，p < 0.001）。在24月龄30%CF组中，SERCA2（+36%）和NCX（+46%）转录本已经出现积累增加，但RyR2没有，而在24月龄15%CF组中三种转录本均有积累。在4月龄大鼠中，仅15%CF组的SERCA2（+26%）、NCX（+35%）和RyR2（+81%）mRNA水平升高。无论4月龄还是24月龄心脏，无论流量减少程度如何，相应的钙调节蛋白水平均未改变。
低流量缺血在成年和衰老心脏中均不会导致钙调节蛋白丢失。在衰老心脏中，冠脉流量减少程度较小时发生的钙处理蛋白编码mRNA增加以及心肌功能受损，表明衰老过程中对低流量缺血的易感性更高。
