2 COMPONENTS OF TRANSIENT OUTWARD CURRENT IN CANINE VENTRICULAR MYOCYTES
2 COMPONENTS OF TRANSIENT OUTWARD CURRENT IN CANINE VENTRICULAR MYOCYTES
复制标题
DOI：
10.1161/01.res.64.4.633
复制
发表时间：
1989-04-01
影响因子：
20.1
通讯作者：
HOFFMAN, BF
中科院分区：
文献类型：
--
作者：
TSENG, GN;HOFFMAN, BF
心脏动作电位第一相的复极很重要，因为它可能影响部分去极化组织的脉冲传导和动作电位时程。因此，了解潜在电流的特性和调节是很重要的。在约50%的犬心室肌细胞中，动作电位表现为快速复极的1相，并在1相与平台之间有一个明显的缺口。瞬时外向电流对这两种情况都有影响。该电流由两个分量组成：一个被4-氨基吡啶阻断(Ito1)，另一个被锰阻断(Ito2)。在目前的研究中，我们将每一种成分与另一种成分隔离开来。两者的激活阈值都在-30到-20 mV之间。在相同电压下，I1to1比Ito2大，峰值时间短。I1to1的峰值电流-电压关系几乎是线性的，而I1to2的峰值电流-电压关系是钟形的。Ito1在持续去极化过程中衰变，呈单一指数时间过程：？在所有电压下，<；30毫秒。它从失活中恢复过来，具有电压依赖的时间过程：tau。=-90 mV时为70毫秒，-40 mV时为720毫秒。升高[Ca~(2+)]o或异丙肾上腺素可使Ito2升高。它被咖啡因、兰尼定或之前的瞬时内向电流抑制，这表明它被肌浆网释放的细胞内钙激活。我们得出的结论是，犬心室中的Ito1和Ito2与许多其他心脏组织中的Ito1和Ito2相似，但Ito1的动力学速度明显快于其他组织。
Repolarization during phase 1 of cardiac action potential is important in that it may influence both impulse conduction in partially de polarized tissue and action potential duration. Thus, it is important to know the properties and regulation of the underlying currents. In about 50% of canine ventricular myocytes, the action potential displays a phase 1 of fast repolarization and a prominent notch between phase 1 and the plateau. A transient outward current is responsible for both. This current is composed of two components: one (Itol) blocked by 4-aminopyridine and the other (Ito2) blocked by manganese. In the present study, we characterized each of the components in isolation from the other. Both had an activation threshold between-30 and -20 mV. At the same voltage, I1to1 was larger than Ito2 and had a shorter time to peak. The peak current-voltage relationship for I1to1 was almost linear, but that for I1to2 was bell-shaped. Ito1 decayed during sustained depolarization with a single exponential time course: .tau. < 30 msec at all voltages. It recovered from inactivation with a voltage-dependent time course: .tau. = 70 msec at -90 mV and 720 msec at -40 mV. Ito2 was augmented by elevating [Ca2+]o or by isoproterenol. It was inhibited by caffeine, ryanodine, or a preceding transient inward current, suggesting that it was activated by intracellular calcium released from sarcoplasmic reticulum. We conclude that Ito1 and Ito2 in canine ventricle are similar to those described for many other cardiac tissues but the kinetics of Ito1 are significantly faster than in other tissues.