Evidence against the role of intracellular calcium dynamics in ventricular fibrillation.
Evidence against the role of intracellular calcium dynamics in ventricular fibrillation.
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反对细胞内钙动力学在心室颤动中作用的证据。
DOI：
10.1161/circresaha.108.175901
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发表时间：
2008
影响因子：
20.1
通讯作者：
Zaitsev,AlexeyV
中科院分区：
文献类型：
--
作者：
Warren,Mark;Zaitsev,AlexeyV
在我们最近的出版物中，我们认为细胞内钙（Cai）动力学不是维持心室颤动（VF）的重要机制。我们的论点基于两个主要观察结果：（1）Cai瞬变被动地沿着整个小波跨度（除了小波尖端）沿着光学动作电位;（2）用BAPTA-AM螯合Cai并没有改变VF期间波破裂（WB）的发生率。Ogawa等人2在给循环研究的信中提出了一个问题，即我们的BAPTA试验无效，因为我们实验中的BAPTA灌注时间（10分钟）太短，无法达到显著效果。为了支持这一说法，Ogawa等人引用了他们自己（未发表）的Langendorff灌注兔心脏结果，表明20 μmol/L BAPTA-AM灌注30分钟后，快速起搏引起Cai短暂交替并最终引发VF，而BAPTA-AM灌注70分钟后，Cai短暂交替不再存在，仅可诱导单形性室性心动过速。2针对这一批评，我们首先提到，实现Cai瞬变抑制所需的BAPTA-AM输注持续时间可能因实验条件而异。Ogawa等人2报告的观察结果（BAPTA-AM灌注30分钟不足以达到效果）不能扩展到一般情况。例如，Marbán等3在BAPTA-AM输注10 - 20分钟后能够完全消除Cai瞬变和收缩。因此，BAPTA-AM输注的持续时间几乎不是评估药物作用的适当或充分的参数。应提供对Cai瞬态振幅和/或收缩性的一些估计，以确保确实存在该效应。与Ogawa等人提到的未发表的结果不同，2我们发表的结果1包括对BAPTA-AM效应的直接评估。具体而言，我们表明，在BAPTA-AM输注后，左心室发展压力（LV-devP）和Cai瞬时振幅显著降低（分别为对照值的12.2%和30.5%）。注意，Rhod-2荧光相对于钙浓度的非线性应高估BAPTA-AM输注后残留Cai瞬变的幅度。因为在我们的研究中校准Rhod-2信号是不可行的或至少是不实际的，所以我们更多地依赖于LV-devP作为BAPTA-AM有效性的指标。因为，尽管LV-devP降低了88%，WB发生率保持不变，1我们推断Cai循环不是VF维持的主要机制。[1]有人可能会认为，即使Cai循环的这种残余水平仍然足以在Cai瞬变和导致WB的动作电位之间提供假设的不稳定反馈。4，5为了使这种可能性更小，我们进行了额外的实验，重点是用BAPTA-AM完全消除Cai瞬变的目标。这不是一件容易的事。我们不能遵循Ogawa等人2描述的方案，因为根据我们的经验，用结晶溶液长时间（20分钟）灌注猪心脏会导致水肿，这本身可能导致VF减慢和规则化。6、当
In our recent publication, 1 we argued that intracellular calcium (Cai) dynamics is not an essential mechanism of the maintenance of ventricular fibrillation (VF). Our argument was based on 2 major observations:(1) Cai transient passively followed the optical action potential along the entire wavelet span, except at the very wavelet tip; and (2) chelating Cai with BAPTA-AM did not change the incidence of wave break (WB) during VF. In their letter to Circulation Research, Ogawa et al2 raised a concern that our BAPTA test is not valid because the time of BAPTA perfusion in our experiments (10 minutes) was too short to achieve a significant effect. To support this statement, Ogawa et al referred to their own (unpublished) results in Langendorff-perfused rabbit hearts indicating that after 30 minutes of perfusion with 20 μmol/L BAPTA-AM, rapid pacing caused Cai transient alternans and eventual initiation of VF, whereas, after 70 minutes of BAPTA-AM perfusion, Cai transient alternans was no longer present and only monomorphic ventricular tachycardia could be induced. 2 In response to this critique, we first mention that duration of BAPTA-AM infusion necessary to achieve suppression of Cai transient may vary depending on experimental conditions. The observation reported by Ogawa et al2 that 30-minute perfusion with BAPTA-AM was not sufficient to achieve the effect cannot be extended to the general case. For example, Marbán et al3 were able to achieve complete abolishment of Cai transient and contraction after 10 to 20 minutes of BAPTA-AM infusion. Thus, the duration of BAPTA-AM infusion is hardly an adequate or sufficient parameter to assess the drug effect. Some estimation of Cai transient amplitude and/or contractility should be provided to ensure that the effect is indeed present. Unlike the unpublished results referred to by Ogawa et al, 2 our published results1 included direct assessment of BAPTA-AM effects. Specifically, we showed that the left ventricular developed pressure (LV-devP) and Cai transient amplitude were significantly decreased after BAPTA-AM infusion (to 12.2% and 30.5% of control values, respectively). Note that nonlinearity of Rhod-2 fluorescence with respect to calcium concentration should overestimate the amplitude of residual Cai transient after BAPTA-AM infusion. Because it was not feasible or at least practical to calibrate Rhod-2 signal in our study, we relied more on LV-devP as an indicator of BAPTA-AM effectiveness. Because, despite 88% decrease in LV-devP, WB incidence remained unchanged, 1 we reasoned that Cai cycling is not a major mechanism of VF maintenance. 1One may argue that even this residual level of Cai cycling can still be sufficient to provide the hypothetical destabilizing feedback between the Cai transient and the action potential leading to WB. 4, 5 To make this possibility even less likely, we performed additional experiments focusing on the goal of complete abolishment of Cai transient with BAPTA-AM. It was not an easy task. We could not follow the protocol described by Ogawa et al2 because, in our experience, long (20 minutes) perfusion of porcine hearts with crystalline solutions results in edema, which in itself may lead to slowing and regularization of VF. 6 On the other hand, when