Functional Expression of L-Type Cardiac Calcium Channels in Mammalian Cell in in vivo and in vitro by Use of Adenovirus.

(1)单通道亚电导的形成是l型Ca^2^+通道的独特特征之一。α亚基表现出通道的主要功能，但α亚基是否能够单独产生亚电导仍不确定。(2)我们通过研究在中国仓鼠成纤维细胞（CHW）细胞中表达的克隆心脏α亚基的单通道电流来验证这一点，研究了心脏β亚基是否共表达。(3) α亚基表现出4种不同的电导水平（22.7、14.3、6.2和3.2 pS）。(4) β亚基的共表达在不改变电导值的情况下显著增加了所有四个电导水平的开口数量。(5)在全细胞箝位研究中，a1通道和α / β通道均在电压阶跃后-10 ms产生峰值电流。随着β亚基的共表达，最大峰值电流增加了-5倍，分数电导曲线向负电位移动了-10毫微米。(6)在单通道研究中，随着β亚基的共表达，(1)通道打开的平均可用时间增加，(2)突发持续时间略有增加，(3)平均第一潜伏期缩短，(4)平均打开时间增加，产生第二次打开状态，(5)平均关闭时间不变。

(1) Formation of single channel subconductance is one of the unique characteristics of the L-type Ca^2^+ channel. The alpha, subunit exhibits a primary function of the channel, it remains uncertain whether alpha subunit alone is able to produce subconductance.(2) We tested this by studying single channel currents of cloned cardiac alpha subunit expressed in Chinese hamster fibroblast (CHW) cells, with/without coexpression of cardiac beta subunit.(3) The alpha, subunit exhibited four distinct levels of conductance (22.7, 14.3, 6.2 and 3.2 pS).(4) Coexpression of beta subunit significantly increased the number of openings in all four levels of conductance without changing the conductance values.(5) In whole-cell clamp study, both a1 channel and alpha, /beta channel yielded currents that peaked at -10 ms after voltage step. With coexpression of the beta subunit, the maximum peak currents were increased by -5 times and the fractional conductance curve were shifted to the negative potential by -10 mY.(6) In single channel study, with coexpression of the beta subunit,(1) The mean available time for channel openings was incresed,(2) The burst duration was marginally increased,(3) The mean first latency was shortened,(4) The mean open time was increased, yielding a second open state,(5) The mean closed times were unchanged.