Townsend C, Rosenberg R L
Department of Pharmacology, University of North Carolina, Chapel Hill 27599-7365, USA.
J Membr Biol. 1995 Sep;147(2):121-36. doi: 10.1007/BF00233541.
We have characterized a voltage-sensitive chloride channel from cardiac sarcoplasmic reticulum (SR) following reconstitution of porcine heart SR into planar lipid bilayers. In 250 mM KCl, the channel had a main conductance level of 130 pS and exhibited two substrates of 61 and 154 pS. The channel was very selective for Cl- over K+ or Na+ (PK+/PCl- = 0.012 and PNa+/PCl- approximately 0.040). It was permeable to several anions and displayed the following sequence of anion permeability: SCN- > I- > NO3- approximately Br- > Cl- > F- > HCOO-. Single-channel conductance saturated with increasing Cl- concentrations (Km = 900 mM and gamma max = 488 pS). Channel activity was voltage dependent, with an open probability ranging from approximately 1.0 around 0 mV to approximately 0.5 at +80 mV. From -20 to +80 mV, channel gating was time-independent. However, at voltages below -40 mV the channel entered a long-lasting closed state. Mean open times varied with voltage, from approximately 340 msec at -20 mV to approximately 6 msec at +80 mV, whereas closed times were unaffected. The channel was not Ca(2+)-dependent. Channel activity was blocked by disulfonic stilbenes, arylaminobenzoates, zinc, and cadmium. Single-channel conductance was sensitive to trans pH, ranging from approximately 190 pS at pH 5.5 to approximately 60 pS at pH 9.0. These characteristics are different from those previously described for Cl- channels from skeletal or cardiac muscle SR.
在将猪心脏肌浆网（SR）重构到平面脂质双分子层后，我们对其中的一种电压敏感性氯离子通道进行了特性描述。在250 mM KCl中，该通道的主要电导水平为130 pS，并表现出61和154 pS的两种亚电导状态。该通道对Cl-的选择性远高于K+或Na+（PK+/PCl- = 0.012，PNa+/PCl-约为0.040）。它对几种阴离子具有通透性，并呈现出以下阴离子通透性顺序：SCN- > I- > NO3- ≈ Br- > Cl- > F- > HCOO-。单通道电导随着Cl-浓度的增加而饱和（Km = 900 mM，γmax = 488 pS）。通道活性依赖于电压，开放概率在0 mV左右约为1.0，在+80 mV时约为0.5。在-20至+80 mV范围内，通道门控与时间无关。然而，在低于-40 mV的电压下，通道进入一个持久的关闭状态。平均开放时间随电压变化，从-20 mV时的约340毫秒到+80 mV时的约6毫秒，而关闭时间不受影响。该通道不依赖Ca(2+)。通道活性被二磺酸芪、芳氨基苯甲酸、锌和镉所阻断。单通道电导对跨膜pH敏感，在pH 5.5时约为190 pS，在pH 9.0时约为60 pS。这些特性与先前描述的骨骼肌或心肌SR中的Cl-通道不同。
