Kamp T J, Sanguinetti M C, Miller R J
Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637.
Circ Res. 1989 Feb;64(2):338-51. doi: 10.1161/01.res.64.2.338.
The modulation of L-type voltage sensitive calcium channels in isolated guinea pig ventricular myocytes by the dihydropyridine (+)-202-791 was examined with the whole-cell voltage-clamp technique with 1.8 mM Ba or Ca as the charge carrier. Striking voltage- and use-dependent effects of the dihydropyridine calcium channel "agonist" (+)-202-791 were revealed. From a holding potential of -60 mV, depolarizing test pulses in the presence of (+)-202-791 demonstrated a concentration-dependent (EC50, 177 nM) increase in the measured peak inward barium current compared to control. In contrast, more depolarized holding potentials (greater than or equal to -30 mV) (+)-202-791 caused a biphasic effect on the peak inward current resulting in a transient enhancement followed by a steady-state block. A saturable, concentration-dependent hyperpolarizing shift in the voltage dependence of current inactivation was observed in the presence of (+)-202-791 with an EC50 of 10.2 nM. The voltage dependence of current activation was also shifted in the hyperpolarizing direction in the presence of (+)-202-791. A use-dependent relative block by (+)-202-791 was observed after repetitive depolarizing test pulses at a frequency of 2 Hz. Thus, the single enantiomer (+)-202-791 can result in either an increase in the whole cell calcium channel current (favored by hyperpolarized holding potentials and low rates of stimulation) or block of calcium channel current (favored by depolarized holding potentials and high rates of stimulation). Various combinations of (-)-202-791, a reported calcium channel antagonist, and (+)-202-791 resulted in intermediate effects on voltage sensitive calcium or barium currents compared with the presence of either enantiomer alone, and no clear cooperative interactions between the enantiomers were observed in contrast to a previous single channel study (Kokuban S, Prod'ham B, Becker C, Porzig H, Reuter H: Studies on Ca channels in intact cardiac cells: Voltage-dependent effects and cooperative interaction of dihydropyridine enantiomers. Mol Pharmacol 1986;30:571-584). The results are discussed in relation to the possible presence of multiple dihydropyridine receptors associated with the voltage sensitive calcium channel.
运用全细胞膜片钳技术，以1.8 mM Ba或Ca作为电荷载体，研究了二氢吡啶（+）-202-791对豚鼠离体心室肌细胞L型电压敏感性钙通道的调节作用。研究揭示了二氢吡啶类钙通道“激动剂”（+）-202-791显著的电压依赖性和使用依赖性效应。从-60 mV的钳制电位开始，在（+）-202-791存在的情况下，去极化测试脉冲显示，与对照组相比，测量到的内向钡电流峰值呈浓度依赖性增加（EC50为177 nM）。相比之下，在更去极化的钳制电位（大于或等于-30 mV）下，（+）-202-791对内向电流峰值产生双相效应，导致短暂增强，随后是稳态阻断。在（+）-202-791存在的情况下，观察到电流失活的电压依赖性出现饱和的、浓度依赖性的超极化偏移，EC50为10.2 nM。在（+）-202-791存在的情况下，电流激活的电压依赖性也向超极化方向偏移。在2 Hz频率的重复去极化测试脉冲后，观察到（+）-202-791存在使用依赖性相对阻断。因此，单一对映体（+）-202-791可导致全细胞钙通道电流增加（超极化钳制电位和低刺激频率有利于此）或钙通道电流阻断（去极化钳制电位和高刺激频率有利于此）。与单独存在任何一种对映体相比，报道的钙通道拮抗剂（-）-202-791和（+）-202-791的各种组合对电压敏感性钙电流或钡电流产生中间效应，并且与之前的单通道研究（Kokuban S，Prod'ham B，Becker C，Porzig H，Reuter H：完整心肌细胞中钙通道的研究：二氢吡啶对映体的电压依赖性效应和协同相互作用。Mol Pharmacol 1986；30：571-584）相反，未观察到对映体之间明显的协同相互作用。结合与电压敏感性钙通道相关的多种二氢吡啶受体可能存在的情况对结果进行了讨论。
