Bkaily G, Jacques D, Yamamoto T, Sculptoreanu A, Payet M D, Sperelakis N
Department of Physiology and Biophysics, Faculty of Medicine, Université de Sherbrooke, Qué, Canada.
Can J Physiol Pharmacol. 1988 Aug;66(8):1017-22. doi: 10.1139/y88-166.
Membrane slow inward currents of 3-day-old embryonic chick single heart cells were investigated using the whole-cell patch clamp technique. In a solution containing only Na+ ions and in the presence of tetrodotoxin and Mn2+, the inward current-voltage relationship presented two maxima, confirming the existence of two different voltage-dependent slow inward currents. The first type, a fast transient slow inward current (Isi (ft], was activated from a holding potential of -80 mV and showed fast activation and inactivation. This current was highly sensitive to melittin (10(-8) M) and insensitive to low concentrations of desmethoxyverapamil [-)D888, 10(-9)-10(-6) M). Depolarizing voltage steps from a holding a potential of -50 mV activated two components of the slow inward current, i.e., a slow and a sustained current (Isi(sts] that showed a slow inactivation followed by a slow inactivation and a sustained component. Melittin at a high concentration (10(-4)M) completely blocked the slow transient component (Isi(st] and left unblocked the sustained component (Isi(s]. Both components (Isi(st) and Isi(s] were blocked by verapamil (10(-5)M) and low concentrations of (-)D888 (10(-8)-10(-6)M).
采用全细胞膜片钳技术研究了3日龄鸡胚单个心脏细胞的膜慢内向电流。在仅含Na⁺离子的溶液中，以及在河豚毒素和Mn²⁺存在的情况下，内向电流-电压关系呈现出两个最大值，证实存在两种不同的电压依赖性慢内向电流。第一种类型，快速瞬态慢内向电流（Isi(ft)），从 -80 mV的钳制电位激活，表现出快速激活和失活。该电流对蜂毒肽（10⁻⁸ M）高度敏感，对低浓度的去甲氧基维拉帕米（-）D888（10⁻⁹ - 10⁻⁶ M）不敏感。从 -50 mV的钳制电位进行去极化电压阶跃激活了慢内向电流的两个成分，即一个慢电流和一个持续电流（Isi(sts)），后者表现出缓慢失活，随后是一个缓慢失活和一个持续成分。高浓度（10⁻⁴ M）的蜂毒肽完全阻断了慢瞬态成分（Isi(st)），而持续成分（Isi(s)）未被阻断。两种成分（Isi(st)和Isi(s)）均被维拉帕米（10⁻⁵ M）和低浓度的（-）D888（10⁻⁸ - 10⁻⁶ M）阻断。
