Effect of twitch interval duration on the contractile function of subsequent twitches in isolated rat, rabbit, and dog myocardium under physiological conditions.
Effect of twitch interval duration on the contractile function of subsequent twitches in isolated rat, rabbit, and dog myocardium under physiological conditions.
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DOI：
10.1152/japplphysiol.01170.2010
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发表时间：
2011-07
影响因子：
3.3
通讯作者：
Ying Xu;M. Monasky;Nitisha Hiranandani;K. M. Haizlip;G. Billman;P. Janssen
中科院分区：
文献类型：
--
作者：
Ying Xu;M. Monasky;Nitisha Hiranandani;K. M. Haizlip;G. Billman;P. Janssen
许多研究表明，刺激频率的变化会导致心肌收缩力的改变。然而，目前还不清楚在频率变化后直接发生了什么变化，以及哪些变化是导致改变稳态的缓慢过程的结果，这是在刺激频率变化后发生的。为了区分即刻反应和缓慢反应，我们使用最近开发的随机起搏方案评估了两种具有明显不同钙（Ca（2+））处理特性的物种的收缩功能。在离体犬和大鼠右心室小梁，抽搐收缩在五个不同的周期长度内的生理范围内的每个物种随机周围的稳态频率。我们发现，在这两个物种中，周期长度的持续时间之前分析抽搐（主要）正相关的分析抽搐力增加。与此形成鲜明对比的是，周期长度，一个和两个以上从分析的抽搐（“二级”和“三级”），显示出与分析的抽搐力的负相关性。在另外的实验中，对兔小梁细胞内Ca（2+）瞬变的评估显示，舒张期Ca（2+）水平与收缩功能结果密切相关。犬（51%）和大鼠（71%）之间主要周期长度的相对贡献不同，而在两个物种中均未观察到对弛豫时间的显著影响。通过使用随机循环长度，我们区分了内在反应与频率依赖性激活对肌丝特性和Ca（2+）处理的信号介导效应。
Many studies have shown that a change in stimulation frequency leads to altered contractility of the myocardium. However, it remains unclear what changes occur directly after a change in frequency and which ones are a result of the slow processes that lead to the altered homeostasis, which develops after a change in stimulation frequency. To distinguish the immediate from the slow responses, we assessed contractile function in two species that have distinctively different calcium (Ca(2+))-handling properties using a recently developed, randomized pacing protocol. In isolated dog and rat right ventricular trabeculae, twitch contractions at five different cycle lengths within the physiologic range of each species were randomized around a steady-state frequency. We found, in both species, that the duration of the cycle length just prior to the analyzed twitch (primary) positively correlated with the increased force of the analyzed twitch. In sharp contrast, the cycle lengths, one and two more removed from the analyzed twitch ("secondary" and "tertiary"), displayed a negative correlation with force of the analyzed twitch. In additional experiments, assessment of intracellular Ca(2+) transients in rabbit trabeculae revealed that diastolic Ca(2+) levels were closely correlated to contractile function outcome. The relative contribution of the primary cycle length was different between dog (51%) and rat (71%), whereas in neither species was a significant effect on relaxation time observed. With the use of randomized cycle lengths, we have distinguished the intrinsic response from the signaling-mediated effects of frequency-dependent activation on myofilament properties and Ca(2+) handling.