Cognard C, Romey G, Galizzi J P, Fosset M, Lazdunski M
Proc Natl Acad Sci U S A. 1986 Mar;83(5):1518-22. doi: 10.1073/pnas.83.5.1518.
The whole-cell patch-clamp technique has been used to analyze the properties of the dihydropyridine-sensitive Ca2+ channel in rat skeletal muscle cells (myoballs) in culture. The potential dependence of Ca2+-channel activation is similar to that observed in cardiac cells. However, the skeletal muscle Ca2+ channel is activated more slowly (by a factor of about 10). The voltage dependence of Ca2+-channel inactivation indicates a half-maximal inactivation (Vh0.5) at -72 mV as compared to Vh0.5 = -35 mV for cardiac cells. Blockade of the skeletal muscle Ca2+ channel by the dihydropyridine (+)-PN 200-110 is voltage dependent, with a half-maximal effect (K0.5) of 13 nM for an application of the drug to the myoball membrane held at -90 mV and of 0.15 nM for an application at a potential of -65 mV. The 100-fold difference in apparent affinity is interpreted as a preferential association of PN 200-110 with the inactivated form of the Ca2+ channel. The K0.5 value found from electrophysiological experiments for the binding to the inactivated state (K0.5 = 0.15 nM) is nearly identical to the equilibrium dissociation constant found from binding experiments with (+)-[3H]PN 200-110 using transverse-tubular membranes (Kd = 0.22 nM). The dihydropyridine activator Bay K8644 acts by increasing Ca2+ current amplitude and by slowing down deactivation.
全细胞膜片钳技术已被用于分析培养的大鼠骨骼肌细胞（肌球）中二氢吡啶敏感的Ca2+通道的特性。Ca2+通道激活的电位依赖性与在心肌细胞中观察到的相似。然而，骨骼肌Ca2+通道的激活更慢（约慢10倍）。Ca2+通道失活的电压依赖性表明，与心肌细胞的Vh0.5 = -35 mV相比，在-72 mV时出现半最大失活（Vh0.5）。二氢吡啶（+）-PN 200-110对骨骼肌Ca2+通道的阻断是电压依赖性的，当将药物施加于保持在-90 mV的肌球膜时，半最大效应（K0.5）为13 nM，而在-65 mV电位下施加时为0.15 nM。表观亲和力的100倍差异被解释为PN 200-110与Ca2+通道失活形式的优先结合。从电生理实验中得出的与失活状态结合的K0.5值（K0.5 = 0.15 nM）与使用横管膜进行的（+）-[3H]PN 200-110结合实验得出的平衡解离常数（Kd = 0.22 nM）几乎相同。二氢吡啶激活剂Bay K8644通过增加Ca2+电流幅度和减慢失活来起作用。
