Miklós Zsuzsa, Ivanics Tamás, Roemen Theo H M, van der Vusse Ger J, Dézsi László, Szekeres Mária, Kemecsei Péter, Tóth András, Kollai Márk, Ligeti László
Institute of Human Physiology and Clinical Experimental Research, Semmelweis University, Budapest, Hungary.
Mol Cell Biochem. 2003 Aug;250(1-2):115-24. doi: 10.1023/a:1024998200846.
The main aim of this study was to assess the kinetics of intracellular free calcium (Ca(2+)i) handling by isolated rat hearts rendered ischemic for 30 min followed by 30 min of reperfusion analyzing the upstroke and downslope of the Ca(2+)i transient. Changes in mechanical performance and degradation of membrane phospholipids--estimated by tissue arachidonic acid content--were correlated with Ca(2+)i levels of the heart. The fluorescence ratio technique was applied to estimate Ca(2+)i. The disappearance of mechanical activity of the heart preceded that of the Ca(2+)i transient in the first 2 min of ischemia. The slope of upstroke of the Ca(2+)i transient, reflecting Ca2+ release, decreased by 60%, while the duration of the downslope of the transient, reflecting Ca2+ sequestration, expressed a significant prolongation (105 +/- 17 vs. 149 +/- 39 msec) during the first 3 min of ischemia. At about 20 min of ischemia end-diastolic pressure expressed a 3.5-fold increase (contracture) when the fluorescence ratio showed a 2-fold elevation. Reperfusion was accompanied with a further precipitous increase in end-diastolic pressure, while resting Ca(2+)i remained at end-ischemic levels. Increases in the arachidonic acid (AA) content of the ischemic and postischemic hearts were proportional to Ca(2+)i levels. In summary, the present findings indicate that both calcium release and removal are hampered during the early phase of ischemia. Moreover, a critical level of Ca(2+)i and a critical duration of ischemia may exist to provoke contracture of the heart. Upon reperfusion the hearts show membrane phospholipid degradation and signs of stunning exemplified by elevated AA levels, partial recovery of Ca(2+)i handling and sustained depression of mechanical performance.
本研究的主要目的是评估离体大鼠心脏在缺血30分钟后再灌注30分钟时细胞内游离钙（Ca(2+)i）处理的动力学，分析Ca(2+)i瞬变的上升支和下降支。通过组织花生四烯酸含量估计的机械性能变化和膜磷脂降解与心脏的Ca(2+)i水平相关。应用荧光比率技术估计Ca(2+)i。在缺血的前2分钟，心脏机械活动的消失先于Ca(2+)i瞬变的消失。反映Ca2+释放的Ca(2+)i瞬变上升支斜率下降了60%，而反映Ca2+摄取的瞬变下降支持续时间在缺血的前3分钟显著延长（105±17对149±39毫秒）。在缺血约20分钟时，舒张末期压力增加了3.5倍（挛缩），此时荧光比率升高了2倍。再灌注伴随着舒张末期压力的进一步急剧增加，而静息Ca(2+)i保持在缺血末期水平。缺血和缺血后心脏花生四烯酸（AA）含量的增加与Ca(2+)i水平成正比。总之，目前的研究结果表明，在缺血早期钙的释放和清除均受到阻碍。此外，可能存在一个临界Ca(2+)i水平和一个临界缺血持续时间来引发心脏挛缩。再灌注时，心脏表现出膜磷脂降解和以AA水平升高、Ca(2+)i处理部分恢复和机械性能持续抑制为特征的顿抑迹象。
