Veenstra R D, DeHaan R L
Department of Anatomy and Cell Biology, Emory University Health Science Center, Atlanta, Georgia 30322.
Am J Physiol. 1988 Jan;254(1 Pt 2):H170-80. doi: 10.1152/ajpheart.1988.254.1.H170.
We have recorded single-gap junction-channel currents from pairs of 7-day chick embryo ventricle cells, using the double whole cell patch-clamp technique. Junctional conductance (Gj) was variable from one preparation to the next, ranging from 0.15 to 35.0 nS. Single-channel conductance (gamma j) of the main junctional channel was 166 +/- 51 pS and was independent of Gj; a second conductance level of 60-80 pS was also seen in favorable records. The transition time from the closed to the open state was 285 +/- 153 microseconds, with some slow transitions lasting 1-5 ms. Channels opened and closed stochastically; Gj could be defined by the product of the number of active channels in the junction (N), the mean open-state probability (Po) of the channels, and gamma j. Channel activity was unaffected by cell membrane potential or by transjunctional potential. Po and Gj were reversibly reduced to low levels by 1-octanol or by elevated [Cai], whereas gamma j was unchanged by these agents. The 60-80 pS conductance mechanism was octanol- and Ca-resistant, but it is not clear whether this represents a subconductance level of the main channel or a separate class of smaller channels.
我们使用双全细胞膜片钳技术记录了7日龄鸡胚心室细胞对之间的单间隙连接通道电流。不同标本间的连接电导（Gj）各不相同，范围为0.15至35.0 nS。主要连接通道的单通道电导（γj）为166±51 pS，且与Gj无关；在良好的记录中还可见到60 - 80 pS的第二电导水平。从关闭状态到开放状态的转变时间为285±153微秒，一些缓慢转变持续1 - 5毫秒。通道随机开放和关闭；Gj可由连接中活性通道数量（N）、通道的平均开放概率（Po）以及γj的乘积来定义。通道活性不受细胞膜电位或跨连接电位的影响。Po和Gj可被1 - 辛醇或升高的[Ca]可逆性降低至低水平，而这些试剂对γj没有影响。60 - 80 pS的电导机制对辛醇和钙具有抗性，但尚不清楚这是代表主要通道的亚电导水平还是一类单独的较小通道。
