Direct measurements of SR free Ca reveal the mechanism underlying the transient effects of RyR potentiation under physiological conditions
Direct measurements of SR free Ca reveal the mechanism underlying the transient effects of RyR potentiation under physiological conditions
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DOI：
10.1093/cvr/cvu158
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发表时间：
2014-09-01
影响因子：
10.8
通讯作者：
Eisner, David A.
中科院分区：
文献类型：
--
作者：
Greensmith, David J.;Galli, Gina L. J.;Eisner, David A.
大多数激活收缩的钙离子通过兰尼碱受体（RyR）从肌浆网（SR）释放。RyR的激活剂是否产生收缩期Ca瞬变幅度的持续增加是有争议的。因此，我们的目的是检查的RyR在大型动物的激活的影响，在设计的条件下，尽可能的生理，同时测量SR和细胞质Ca。方法和结果实验进行犬和绵羊心脏的心室肌细胞。用fluo-3测量细胞质Ca，用mag-fura-2测量SR Ca。应用咖啡因导致短暂的增加幅度的收缩期钙瞬变伴随着动作电位时程的增加。这些效应消失的速率常数类似于3 s（-1）。从快速起搏导致心力衰竭的绵羊身上提取的细胞也有类似的效果。钙瞬变幅度的降低伴随着SR钙含量的降低。在此阶段，最大（舒张末期）SR钙含量下降，而最小收缩increased.Conclusions本研究表明，在设计的条件下，尽可能的生理，增强RyR开放没有保持对收缩期钙瞬变的影响。这一结果使得RyR的增强不太可能在正性肌力中具有维持作用。
Aims Most of the calcium that activates contraction is released from the sarcoplasmic reticulum (SR) through the ryanodine receptor (RyR). It is controversial whether activators of the RyR produce a maintained increase in the amplitude of the systolic Ca transient. We therefore aimed to examine the effects of activation of the RyR in large animals under conditions designed to be as physiological as possible while simultaneously measuring SR and cytoplasmic Ca.Methods and results Experiments were performed on ventricular myocytes from canine and ovine hearts. Cytoplasmic Ca was measured with fluo-3 and SR Ca with mag-fura-2. Application of caffeine resulted in a brief increase in the amplitude of the systolic Ca transient accompanied by an increase of action potential duration. These effects disappeared with a rate constant of similar to 3 s(-1). Similar effects were seen in cells taken from sheep in which heart failure had been induced by rapid pacing. The decrease of Ca transient amplitude was accompanied by a decrease of SR Ca content. During this phase, the maximum (end-diastolic) SR Ca content fell while the minimum systolic increased.Conclusions This study shows that, under conditions designed to be as physiological as possible, potentiation of RyR opening has no maintained effect on the systolic Ca transient. This result makes it unlikely that potentiation of the RyR has a maintained role in positive inotropy.