Timin E N, Hering S
Department of Pharmacology and Clinical Pharmacology, St. George's Hospital Medical School, London, United Kingdom.
Biophys J. 1992 Sep;63(3):808-14. doi: 10.1016/S0006-3495(92)81636-3.
The affinity of D600 to calcium channels in the open state has been examined in isolated smooth muscle cells of the rabbit ear artery. Calcium channel currents were measured in high external barium solution by means of the patch-clamp technique. The current inhibition in various D600 concentrations (3-100 microM) on application of trains of short test pulses (20-80 ms) has been studied in nonmodified calcium channels and in cells where the calcium channels were modified by the agonist dihydropyridine (+) 202,791 (100 nM). The kinetics of the peak current decay has been analyzed with a mathematical model which is based on the experimental finding that D600 interacts primarily with calcium channels in the open conformational state. The model approach allows the estimation of drug affinity constants of D600 to the calcium channel in the open conformation. An association rate constant to the open conformational state of D600 of 6.16 x 10(4) M-1 s-1 was estimated. The association rate of the drug was not significantly changed after the calcium channels have been modified with 100 nM (+) 202,791. A method for correction of rate constants for possible drug trapping is discussed.
在兔耳动脉的离体平滑肌细胞中研究了D600对处于开放状态的钙通道的亲和力。采用膜片钳技术在高细胞外钡溶液中测量钙通道电流。在未修饰的钙通道以及钙通道被激动剂二氢吡啶（+）202,791（100 nM）修饰的细胞中，研究了不同浓度D600（3 - 100 microM）在施加短测试脉冲序列（20 - 80 ms）时对电流的抑制作用。利用一个数学模型分析了峰值电流衰减的动力学，该模型基于D600主要与处于开放构象状态的钙通道相互作用这一实验发现。该模型方法能够估计D600对开放构象的钙通道的药物亲和常数。估计出D600对开放构象状态的缔合速率常数为6.16×10⁴ M⁻¹ s⁻¹。在用100 nM（+）202,791修饰钙通道后，药物的缔合速率没有显著变化。讨论了一种针对可能的药物滞留校正速率常数的方法。
