Role of the Kv4.3 K + Channel in Ventricular Muscle

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Abstract
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 (Ito). 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 Ito in canine ventricular myocytes, and probably in human myocytes. Both the Kv4.3 and Kv4.2 channels are likely to contribute to the Ito in rat heart, and differential expression of these two channels can account for observed differences in the kinetic properties of the Ito 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 t...