Aberrant cell-to-cell coupling in Ca2+-overloaded guinea pig ventricular muscles
Aberrant cell-to-cell coupling in Ca2+-overloaded guinea pig ventricular muscles
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DOI：
10.1152/ajpcell.00413.2007
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发表时间：
2008-06-01
影响因子：
5.5
通讯作者：
Ogawa, Yasuo
中科院分区：
文献类型：
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作者：
Kurebayashi, Nagomi;Nishizawa, Hiroto;Ogawa, Yasuo
为了研究心室肌Ca（2+）超负荷时细胞间偶联的变化，我们用多细胞标本研究了单个细胞的Ca（2+）信号和主要缝隙连接通道连接蛋白43（Cx43）的组织化学。从豚鼠心室获得乳头肌，并负载rhod-2。用共聚焦显微镜观察细胞表面Ca（2+）的动态变化。在完整的肌肉中，所有细胞在0.3 X 0.3 mm（2）的视野范围内对场刺激同时显示出Ca（2+）瞬变。在非流动的克雷布斯溶液中高频刺激严重Ca（2+）超载的肌肉，细胞对刺激的反应变得不那么灵敏。此外，经常检测到非同时但连续的Ca（2+）瞬变发作，表明动作电位的传播延迟。两个对齐的细胞之间的发病的时间滞后有时长达100毫秒。类似的滞后也观察到在肌肉与间隙连接通道抑制庚醇。为了研究在Ca（2+）超载的肌肉中Cx43的磷酸化状态是否受到影响，使用特异性抗体测定磷酸化和非磷酸化Cx43的分布。在非钙超载的肌肉中，大多数Cx43被磷酸化，而在严重钙超载的肌肉中，非磷酸化的Cx43显著升高。我们的研究结果表明，在一个小的区域内，几平方毫米的动作电位的传播延迟，可以是一个原因异常传导和微折返在Ca（2+）超载的心脏。Na（+）通道的失活和缝隙连接通讯的抑制可能是细胞间传播延迟的基础。
To investigate how intercellular coupling can be changed during Ca(2+) overloading of ventricular muscle, we studied Ca(2+) signals in individual cells and the histochemistry of the major gap junction channel, connexin43 (Cx43), using multicellular preparations. Papillary muscles were obtained from guinea pig ventricles and loaded with rhod-2. Sequential Ca(2+) images of surface cells were obtained with a confocal microscope. In intact muscles, all cells showed simultaneous Ca(2+) transients in response to field stimulation over a field of view of 0.3 X 0.3 mm(2). In severely Ca(2+)-overloaded muscles, obtained by high-frequency stimulation in nonflowing Krebs solution, cells became less responsive to stimulation. Furthermore, nonsimultaneous but serial onsets of Ca(2+) transients were often detected, suggesting a propagation delay of action potentials. The time lag of the onset between two aligned cells was sometimes as long as 100 ms. Similar lags were also observed in muscles with gap junction channels inhibited by heptanol. To investigate whether the phosphorylation state of Cx43 is affected in Ca(2+)-overloaded muscles, the distributions of phosphorylated and nonphosphorylated Cx43 were determined using specific antibodies. Most of the Cx43 was phosphorylated in the nonoverloaded muscles, whereas nonphosphorylated Cx43 was significantly elevated in severely Ca(2+)-overloaded muscles. Our results suggest that the propagation delay of action potential within a small area, a few square millimeters, can be a cause of abnormal conduction and a microreentry in Ca(2+)-overloaded heart. Inactivation of Na(+) channels and inhibition of gap junctional communication may underlie the cell-to-cell propagation delay.