Dixon J E, Shi W, Wang H S, McDonald C, Yu H, Wymore R S, Cohen I S, McKinnon D
Department of Neurobiology and Behavior, State University of New York at Stony Brook 11794-5230, USA.
Circ Res. 1996 Oct;79(4):659-68. doi: 10.1161/01.res.79.4.659.
The expression of 15 different K+ channels in canine heart was examined, and a new K+ channel gene (Kv4.3), which encodes a rapidly inactivating K+ current, is described. The Kv4.3 channel was found to have biophysical and pharmacological properties similar to the native canine transient outward current (I(to)). The Kv4.3 gene is also expressed in human and rat heart. It is concluded that the Kv4.3 channel underlies the bulk of the I(to) in canine ventricular myocytes, and probably in human myocytes. Both the Kv4.3 and Kv4.2 channels are likely to contribute to the I(to) in rat heart, and differential expression of these two channels can account for observed differences in the kinetic properties of the I(to) in different regions of rat ventricle. There are significant differences in the pattern of K+ channel expression in canine heart, compared with rat heart, and these differences may be an adaptation to the different requirements for cardiac function in mammals of markedly different sizes. It is possible that the much longer ventricular action potential duration observed in canine heart compared with rat heart is due, in part, to the lower levels of Kv1.2, Kv2.1, and Kv4.2 gene expression in canine heart.
研究了犬心脏中15种不同钾离子通道的表达情况，并描述了一种新的钾离子通道基因（Kv4.3），该基因编码一种快速失活的钾离子电流。发现Kv4.3通道具有与天然犬类瞬时外向电流（I(to)）相似的生物物理和药理学特性。Kv4.3基因也在人类和大鼠心脏中表达。得出的结论是，Kv4.3通道是犬心室肌细胞中大部分I(to)的基础，可能也是人类心肌细胞中I(to)的基础。Kv4.3和Kv4.2通道可能都对大鼠心脏中的I(to)有贡献，这两种通道的差异表达可以解释在大鼠心室不同区域观察到的I(to)动力学特性差异。与大鼠心脏相比，犬心脏中钾离子通道的表达模式存在显著差异，这些差异可能是对大小明显不同的哺乳动物心脏功能不同需求的一种适应。与大鼠心脏相比，犬心脏中观察到的心室动作电位持续时间长得多，这可能部分归因于犬心脏中Kv1.2、Kv2.1和Kv4.2基因表达水平较低。
