A study on the excitation-contraction coupling of myocardium - Analysis on isolated, perfused hearts using multi-nuclear NMR methods.

本研究目的在于评估离体灌流心脏的心肌兴奋-收缩（E-C）偶联。（1）电-心偶联终点评价方法的建立：采用氟核磁共振（~ 1F-NMR）技术，结合Ca^&lt;2+螯合剂5 F-BAPTA，测定灌流心脏细胞内Ca^&lt;2+浓度（[Ca^&lt;2+]_i）<19>。钙瞬变可以通过这种具有门控的F-NMR技术来评估。用Ryanodine快速起搏诱发强直时左室等容压测定肌丝最大Ca ^&lt;2 +&gt;激活力（MCAP）。（2）缺血早期收缩功能衰竭的机制：无机磷酸盐（Pi）使MCAP降低，质子（H^+）使MCAP降低，Ca^&lt;2+&gt;-敏感性改变。 关于我们 高Ca。因此，这些结果表明，缺血期间Pi和H^+的增加导致早期收缩衰竭。（3）顿抑心肌的病理生理学：短暂缺血后再灌注可产生长期的收缩衰竭而无坏死（“顿抑心肌”）。顿抑心肌MCAP降低，钙瞬变幅度增加。因此，这些结果表明，这种收缩功能障碍是由于最大Ca^&lt;2+&gt;激活力的降低和Ca^&lt;2+&gt;敏感性向更高Ca的转移以及钙瞬变幅度的反常增加。（4）顿抑心肌的发病机制：缺血再灌注时短暂的钙超载导致顿抑心肌收缩功能障碍。直接测定缺血及再灌注后[Ca^&lt;2+&gt;]_i的变化，证实了钙超载的存在。（5）非缺血性钙超载对心肌收缩力的影响：阿霉素增加心肌[Ca^&lt;2+&gt;]_i而无缺血性改变，引起心肌收缩障碍。因此，这些结果表明钙超载本身使心脏功能恶化。少

This project aimed on the assessment of excitation-contraction (E-C) coupling in myocardium of isolated, perfused hearts.The following results were obtained in this University-to-University Cooperative Research. (1)Development of the methods to assess the endpoints in E-C coupling: The intracellular concentration of activator Ca^<2+> ([Ca^<2+>]_i) was measured in perfused heart using fluorine nuclear magnetic resonance spectroscopy (^<19>F-NMR) coupled with Ca^<2+> chelator, 5F-BAPTA. Calcium transients could be evaluated by this F-NMR technique with gating. Maximal Ca^<2+>-activated pressure (MCAP), the index of maximal Ca^<2+>-activated force in myofilament was evaluated by left ventricular isovolumic pressure during tetani elicited by the rapid pacing after exposure to ryanodine. (2)Mechanism of early contractile failure during ischemia: It was revealed that inorganic phosphate (Pi) decreases MCAP and proton (H^+) induces both the decrease in MCAP and the shift of Ca^<2+>-sensitivit … More y to higher Ca. Thus, these results indicate that the increase of Pi and H^+ during ischemia causes early contractile failure. (3)Pathophysiology of stunned myocardium: Reperfusion after a brief period of ischemia produces prolonged contractile failure without necrosis ("stunned myocardium"). In stunned myocardium, MCAP decreased and the amplitude of calcium transient increased compared with the control. Thus, these results indicate that this contractile dysfunction is due to the decrease in maximal Ca^<2+>-activated force and the shift of Ca^<2+>-sensitivity to higher Ca with paradoxical increase in amplitude of calcium transients. (4)Pathogenesis of stunned myocardium: Our data suggested that a transient calcium overload during ischemia and reperfusion causes the contractile failure in stunned myocardium. The changes in [Ca^<2+>]_i during ischemia and after reperfusion were also directly measured and the exist of calcium overload was confirmed. (5)Effect of non-ischemic calcium overload on contractility: Doxorubicin increased [Ca^<2+>]_i without ischemic changes and caused contractile disorder. Thus, these results indicate that calcium overload itself deteriorates the cardiac function. Less