Cardiac transient outward potassium current

The cardiac transient outward potassium current (referred to as Ito1 or Ito) is one of the ion currents across the cell membrane of heart muscle cells. It is responsible for the (brief) repolarizing phase 1 of the cardiac action potential (which suceeds depolarisation, and precedes the plateau phase). The Ito is produced by movement of positively charged potassium (K+) ions from the intracellular into the extracellular space. It exhibits rapid activation and inactivation. Ito1 is complemented with Ito2 resulting from Cl− ions to form the transient outward current Ito.

The Ito1 is generated by voltage-gated K+ channels Kv1.4, Kv4.2, and (especially) Kv4.3; these channels undergo ball-and-chain inactivation to terminate the current.

It occurs in atrial, ventricular, and conduction system cells. In ventricular myocardium, it is more potent in the epicardium than the endocardium; this transmural Ito1 gradient underlies the J wave ECG finding.

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.