Surf Wiki
Save to docs
science/biology

From Surf Wiki (app.surf) — the open knowledge base

Cardiac transient outward potassium current

Ion current

Cardiac transient outward potassium current
Summary

Ion current

The cardiac action potential has five phases. I<sub>to1</sub> is active during phase 1, causing a fast [[repolarization]] of the action potential

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 succeeds 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.

Role in disease

  • Reduction in Ito1 density is associated with prolonged action potentials and is a common finding in cardiac disease. :*Ito1 density is significantly lower in the cells of a failing heart in comparison to the cells of a healthy heart. :*There is correlation between decreased Ito1 density and atrial fibrillation. :*Ito activation is inhibited by thyrotropin (TSH). This mechanisms may be one of the reasons for the observation that both bradycardia and atrial fibrillation are common in hypothyroidism.
  • An increase in the Ito1 density caused by a mutation in Kv4.3 can be a cause of Brugada Syndrome.

References

References

  1. (January 2010). "Molecular determinants of cardiac transient outward potassium current (I(to)) expression and regulation". Journal of Molecular and Cellular Cardiology.
  2. "Comprehensive Human Physiology: From Cellular Mechanisms to Integration". Springer.
  3. (2014). "Mayo Clinic Electrophysiology Manual". Mayo Clinic Scientific Press/Oxford University Press.
  4. (May 2001). "The molecular physiology of the cardiac transient outward potassium current (I(to)) in normal and diseased myocardium". Journal of Molecular and Cellular Cardiology.
  5. (August 1993). "Alterations of K+ currents in isolated human ventricular myocytes from patients with terminal heart failure". Circulation Research.
  6. (October 2000). "The ultrarapid and the transient outward K(+) current in human atrial fibrillation. Their possible role in postoperative atrial fibrillation". Journal of Molecular and Cellular Cardiology.
  7. (December 2015). "Thyroid stimulating hormone directly modulates cardiac electrical activity". Journal of Molecular and Cellular Cardiology.
  8. (15 August 2022). "Minor perturbations of thyroid homeostasis and major cardiovascular endpoints-Physiological mechanisms and clinical evidence". Frontiers in Cardiovascular Medicine.
  9. (October 2013). "Both hypothyroidism and hyperthyroidism increase atrial fibrillation inducibility in rats". Circulation: Arrhythmia and Electrophysiology.
  10. (December 2012). "Subclinical Hypothyroidism: An Overlooked Cause of Atrial Fibrillation?". Journal of Atrial Fibrillation.
  11. (July 2011). "Transient outward current (I(to)) gain-of-function mutations in the KCND3-encoded Kv4.3 potassium channel and Brugada syndrome". Heart Rhythm.
Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

electrophysiology cardiac-electrophysiology
Want to explore this topic further?

Ask Mako anything about Cardiac transient outward potassium current — get instant answers, deeper analysis, and related topics.

Research with Mako

Free with your Surf account

Content sourced from Wikipedia, available under CC BY-SA 4.0.

This content may have been generated or modified by AI. CloudSurf Software LLC is not responsible for the accuracy, completeness, or reliability of AI-generated content. Always verify important information from primary sources.

Report