Electric currents applied during refractory period enhance contractility and systolic calcium in the ferret heart
Electric currents applied during refractory period enhance contractility and systolic calcium in the ferret heart
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DOI：
10.1152/ajpheart.00378.2002
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发表时间：
2003-04-01
影响因子：
4.8
通讯作者：
Burkhoff, D
中科院分区：
文献类型：
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作者：
Mohri, S;Shimizu, J;Burkhoff, D
我们探讨了正性肌力作用的机制。在绝对不应期内施加的电流。用Langendorff法灌流雪貂心脏，测定等容左心室压（LVP）和水母发光蛋白。在电极对之间输送双相方波电流（+/-20 mA，总持续时间30 ms）。在不同的细胞外Ca 2+浓度（[Ca 2 +]（o）; 1，2，4和8 mM）下灌注6个心脏。这些信号使LVP从50.0 +/- 9.4增加到70.1 +/- 14.7，从67.5 +/- 11.0增加到79.0 +/- 15.6，从79.3 +/- 21.0增加到87.1 +/- 22.8，在相应的[Ca 2 +]（o）下从84.6 +/- 24.0到91.8 +/- 28.5 mmHg（p < 0.05）。峰值游离细胞内[Ca 2 +]（[Ca 2 +]（i））从0.52 +/- 0.13增加到1.37 +/- 0.23，从0.76 +/- 0.23增加到1.73 +/- 0.14，从1.10 +/- 0.24增加到2.05 +/- 0.33，从1.41 ± 0.36 μ M/ml到2.24 ± 0.36 μ M/ml（P < 0.001）。在使用1 mg/l普萘洛尔和1 mM [Ca 2 +]（o）时，LVP和[Ca 2 +]（i）分别从48.7 +/- 8.18增加到56.3 +/- 6.11 mmHg和从0.61 +/- 0.11增加到1.17 +/- 0.20 μ M（P < 0.05）。总之，正性肌力。这种电流的增加是由于[Ca ~（2+）]（i）峰的增加，而肌丝的Ca ~（2+）反应性没有显著变化。
We investigated the mechanism of positive inotropism. of electric currents applied during the absolute refractory period. Ten Langendorff-perfused ferret hearts were instrumented to measure isovolumic left ventricular pressure (LVP) and the aequorin luminescence. Biphasic squarewave electric currents (+/-20 mA, total duration 30 ms) were delivered between pairs of electrodes. Six hearts were perfused at different extracellular Ca2+ concentrations ([Ca2+](o); 1, 2, 4, and 8 mM). These signals increased LVP from 50.0 +/- 9.4 to 70.1 +/- 14.7, from 67.5 +/- 11.0 to 79.0 +/- 15.6, from 79.3 +/- 21.0 to 87.1 +/- 22.8, and from 84.6 +/- 24.0 to 91.8 +/- 28.5 mmHg at the respective [Ca2+](o) (p < 0.05). Peak free intracellular [Ca2+] ([Ca2+](i)) increased from 0.52 +/- 0.13 to 1.37 +/- 0.23, from 0.76 +/- 0.23 to 1.73 +/- 0.14, from 1.10 +/- 0.24 to 2.05 +/- 0.33, and from 1.41 +/- 0.36 to 2.24 +/- 0.36 mu M/ml, respectively (P < 0.001). With the use of 1 mg/l propranolol with 1 mM [Ca2+](o), LVP and [Ca2+](i) were increased significantly from 48.7 +/- 8.18 to 56.3 +/- 6.11 mmHg and from 0.61 +/- 0.11 to 1.17 +/- 0.20 muM, respectively (P < 0.05). In conclusion, positive inotropism. of such electrical currents was due to increased peak [Ca2+](i) and Ca2+ responsiveness of the myofilaments did not change significantly.