Hata Y, Shimizu J, Hosogi S, Matsubara H, Araki J, Ohe T, Takaki M, Takasago T, Taylor T W, Suga H
Department of Physiology II, Okayama University Medical School, Okayama, 700 Japan.
Jpn J Physiol. 1997 Dec;47(6):521-30. doi: 10.2170/jjphysiol.47.521.
We tested our hypothesis that the O2 wasting of Ca2+ handling in the excitation-contraction (E-C) coupling in ryanodine-treated failing hearts could be reflected by a decrease in the internal Ca2+ recirculation fraction (RF). We have reported, using canine excised cross-circulated hearts, that intracoronary ryanodine (40 nmol/l blood) halved left ventricular contractility without decreasing myocardial O2 consumption for the E-C coupling. We previously suspected this mechanoenergetic state to manifest energy wasting of Ca2+ handling due to ryanodine causing leakage of Ca2+ from the sarcoplasmic reticulum. To test this hypothesis, we analyzed all the sporadic spontaneous cases of postextrasystolic potentiation (PESP) obtained during the ryanodine experiments. We calculated RF from the beat constant of the exponential decay component of not only the monotonic type but also the transient alternans type of PESP. Results showed that ryanodine significantly decreased the beat constant in both types of PESP from about 2 to 1.5 beats and hence RF from 0.6 to 0.5 on the average, supporting the hypothesis. This organ-level systems approach to Ca2+ handling using transient alternans PESP as well as monotonic PESP may help obtain better insights into the mechanoenergetics of failing hearts.
在经雷诺丁处理的衰竭心脏中，兴奋 - 收缩（E - C）偶联过程中钙处理的氧气浪费可通过细胞内钙再循环分数（RF）的降低来反映。我们曾利用犬类离体交叉循环心脏报道过，冠状动脉内注入雷诺丁（40 nmol/l血液）使左心室收缩力减半，但并未降低E - C偶联的心肌耗氧量。我们之前怀疑这种机械能量状态表现为钙处理的能量浪费，原因是雷诺丁导致钙从肌浆网泄漏。为验证这一假设，我们分析了雷诺丁实验期间获得的所有散发性早搏后增强（PESP）的自发情况。我们不仅从单调型PESP，还从瞬态交替型PESP的指数衰减成分的搏动常数计算RF。结果表明，雷诺丁使两种类型PESP的搏动常数均显著降低，从约2次搏动降至1.5次搏动，因此RF平均从0.6降至0.5，支持了该假设。这种利用瞬态交替型PESP以及单调型PESP对钙处理进行的器官水平系统研究方法，可能有助于更深入了解衰竭心脏的机械能量学。
