Slinker B K, Tobias A H
Department of Veterinary and Comparative, Anatomy, Pharmacology, and Physiology, Washington State University, Pullman 99164-6520, USA.
Cardiovasc Res. 1996 Jul;32(1):131-7.
Prior studies have shown that the performance of the left ventricle on any one beat is influenced by the mechanical events of the previous beat, a phenomenon called "previous-beat contraction history". This previous-beat contraction history, which appears to be an interplay between the mechanical events of one contraction and the activation state of the next contraction, could depend, at least in part, on mechanosensitive ion channels. The purpose of this study, therefore, was to test the hypothesis that mechanosensitive ion channels contribute to previous-beat contraction history: If previous-beat contraction history depends on mechanosensitive ion channels, the magnitude of its effect should be decreased by blocking mechanosensitive ion channels.
We performed experiments in buffer-perfused isolated rabbit hearts in which left ventricular pressure and volume were controlled with a servo-motor system. We evaluated the pulse interval-dependent expression of previous-beat contraction history under control conditions (no drug) and in the presence of 100 and 500 microM streptomycin, a blocker of mechanosensitive ion channels.
Under control conditions, previous-beat contraction history nor its dependence on pulse interval was influenced significantly by either concentration of streptomycin.
Mechanosensitive ion channels do not play a role in the expression of previous-beat contraction history in the left ventricle of the isolated rabbit heart.
先前的研究表明，左心室在任何一次搏动时的表现都会受到前一次搏动机械事件的影响，这一现象被称为“前次搏动收缩史”。这种前次搏动收缩史似乎是一次收缩的机械事件与下一次收缩的激活状态之间的相互作用，至少部分可能取决于机械敏感性离子通道。因此，本研究的目的是检验机械敏感性离子通道促成前次搏动收缩史这一假说：如果前次搏动收缩史取决于机械敏感性离子通道，那么通过阻断机械敏感性离子通道，其效应的大小应该会降低。
我们在缓冲液灌注的离体兔心脏上进行实验，使用伺服电机系统控制左心室压力和容积。我们评估了在对照条件下（无药物）以及存在100和500微摩尔链霉素（一种机械敏感性离子通道阻滞剂）时，前次搏动收缩史的脉冲间隔依赖性表达。
在对照条件下，链霉素的任一浓度均未显著影响前次搏动收缩史及其对脉冲间隔的依赖性。
在离体兔心脏的左心室中，机械敏感性离子通道在前次搏动收缩史的表达中不起作用。
