Hasenfuss G, Reinecke H, Studer R, Pieske B, Meyer M, Drexler H, Just H
Universität Freiburg Medizinische Klinik III, Freiburg, FRG.
Basic Res Cardiol. 1996;91 Suppl 2:17-22. doi: 10.1007/BF00795357.
Myocardial function, intracellular calcium and levels of calcium cycling proteins were analyzed in failing and nonfailing human myocardium. Myocardial function was evaluated by the isometric force-frequency relation, and intracellular calcium was studied by aequorin light emission. When stimulation frequency was increased above 30 min-1, there was a continuous increase in isometric tension development in the nonfailing myocardium. In contrast, in failing myocardium, frequency potentiation of contractile force was blunted or inverse. As a consequence, at higher rates of stimulation, twitch tension was reduced significantly in failing compared to nonfailing human myocardium. Aequorin measurements indicated that the contractile deficit in the failing myocardium at higher rates of stimulation is associated with decreased free intracellular calcium concentration. Western blot analysis indicated that in the failing myocardium protein levels of SR-Ca(2+)- ATPase are significantly reduced and protein levels of Na(+)-Ca(2+)- exchanger are significantly increased. Levels of phospholamban are slightly reduced in the failing myocardium, and ryanodine receptor and calsequestrin protein levels are unchanged. There was a close positive correlation between the protein levels of SR-Ca(2+)-ATPase and frequency potentiation of contractile force. From these data, we conclude that in failing compared to nonfailing human myocardium 1) force-frequency relation is blunted or inverse. 2) Frequency-dependence of contractile force is closely correlated with frequency-dependence of intracellular calcium cycling. 3) Protein levels of SR-Ca(2+)-ATPase may determine frequency-dependence of sarcoplasmic reticulum calcium release. 4) Calcium elimination by an increased number of Na(+)-Ca2-exchanger molecules may be a compensatory mechanism to prevent diastolic calcium accumulation in failing myocardium with a reduced number of SR calcium pumps.
对衰竭和非衰竭的人类心肌组织进行了心肌功能、细胞内钙含量及钙循环蛋白水平的分析。通过等长力 - 频率关系评估心肌功能，利用水母发光蛋白发光研究细胞内钙。当刺激频率增加到30次/分钟以上时，非衰竭心肌的等长张力持续增加。相比之下，在衰竭心肌中，收缩力的频率增强减弱或呈反向变化。因此，在较高刺激频率下，与非衰竭人类心肌相比，衰竭心肌的单次收缩张力显著降低。水母发光蛋白测量结果表明，在较高刺激频率下，衰竭心肌的收缩功能缺陷与细胞内游离钙浓度降低有关。蛋白质印迹分析表明，在衰竭心肌中，肌浆网钙ATP酶（SR - Ca(2 +)- ATPase）的蛋白水平显著降低，而钠钙交换体（Na(+)-Ca(2 +)- exchanger）的蛋白水平显著升高。受磷蛋白水平在衰竭心肌中略有降低，而兰尼碱受体和肌集钙蛋白的蛋白水平未发生变化。SR - Ca(2 +)-ATPase的蛋白水平与收缩力的频率增强之间存在密切的正相关。从这些数据中，我们得出结论，与非衰竭人类心肌相比，衰竭心肌：1）力 - 频率关系减弱或呈反向。2）收缩力的频率依赖性与细胞内钙循环的频率依赖性密切相关。3）SR - Ca(2 +)-ATPase的蛋白水平可能决定肌浆网钙释放的频率依赖性。4）通过增加钠钙交换体分子数量来消除钙，可能是一种代偿机制，以防止在肌浆网钙泵数量减少的衰竭心肌中出现舒张期钙蓄积。
