Almassy Janos, Sztretye Monika, Lukacs Balazs, Dienes Beatrix, Szabo Laszlo, Szentesi Peter, Vassort Guy, Csernoch Laszlo, Jona Istvan
Department of Physiology, University of Debrecen, Debrecen, Hungary.
Pflugers Arch. 2008 Oct;457(1):171-83. doi: 10.1007/s00424-008-0504-7. Epub 2008 May 6.
The benzothiazepine derivative K-201 has been suggested as a potential therapeutic agent due to its antiarrhythmogenic action. To understand how the drug alters calcium release from the sarcoplasmic reticulum (SR), we investigated its effects on the SR calcium channel and calcium pump by single channel electrophysiology, whole-cell confocal microscopy, and ATPase activity measurements on control and post-myocardial infarcted (PMI) rat skeletal muscle. In bilayers, K-201 induced two subconductance states corresponding to approximately 24% (S(1)) and approximately 13% (S(2)) of the maximum conductance. Dependence of event frequency and of time spent in S(1) and S(2) on the drug concentration was biphasic both in control and in PMI rats, with a maximum at 50 microM. At this concentration, the channel spends 26 +/- 4% and 24 +/- 4%, respectively, of the total time in these subconductance states at positive potentials, while no subconductances are observed at negative potentials. K-201 altered the frequency of elementary calcium release events: spark frequency decreased from 0.039 +/- 0.001 to 0.023 +/- 0.001 s(-1) sarcomere(-1), while the frequency of embers increased from 0.011 +/- 0.001 to 0.023 +/- 0.001 s(-1) sarcomere(-1). Embers with different amplitude levels were observed after the addition of the drug. K-201 inhibited the Ca(2+) ATPase characterized by IC(50,contr) = 119 +/- 21 muM and n (Hill,contr) = 1.84 +/- 0.48 for control and IC(50,PMI) = 122 +/- 18 microM and n (Hill,PMI) = 1.97 +/- 0.24 for PMI animals. These results suggest that although K-201 would increase the appearance of subconductance states, the overall calcium release is reduced by the drug. In addition, the effect of K-201 is identical on calcium release channels from control and PMI rats.
苯并硫氮䓬衍生物K-201因其抗心律失常作用而被认为是一种潜在的治疗药物。为了解该药物如何改变肌浆网（SR）的钙释放，我们通过单通道电生理学、全细胞膜片钳共聚焦显微镜以及对对照和心肌梗死后（PMI）大鼠骨骼肌进行ATP酶活性测量，研究了其对SR钙通道和钙泵的影响。在脂质双分子层中，K-201诱导出两种亚电导状态，分别对应最大电导的约24%（S(1)）和约13%（S(2)）。在对照大鼠和PMI大鼠中，事件频率以及在S(1)和S(2)状态下所花费时间对药物浓度的依赖性均呈双相，在50 microM时达到最大值。在此浓度下，在正电位时通道分别有26±4%和24±4%的总时间处于这些亚电导状态，而在负电位时未观察到亚电导。K-201改变了基本钙释放事件的频率：火花频率从0.039±0.001降至0.023±0.001 s(-1)肌节(-1)，而余烬频率从0.011±0.001增加至0.023±0.001 s(-1)肌节(-1)。添加药物后观察到了不同幅度水平的余烬。K-201抑制Ca(2+)ATP酶，对照动物的IC(50,contr)=119±21 microM，n(Hill,contr)=1.84±0.48；PMI动物的IC(50,PMI)=122±18 microM，n(Hill,PMI)=1.97±0.24。这些结果表明，尽管K-2会增加亚电导状态的出现，但该药物会降低整体钙释放。此外，K-201对对照大鼠和PMI大鼠的钙释放通道的作用相同。
