Transient outward current in human and rat ventricular myocytes

Area of Science:

• Cardiovascular Physiology
• Cardiac Electrophysiology

Background:

• Transient outward currents (I(to)) play a crucial role in cardiac action potential repolarization.
• Understanding I(to) in human hearts is essential for developing targeted therapies for cardiac arrhythmias.

Purpose of the Study:

• To investigate and compare the electrophysiological characteristics of transient outward currents (I(to)) in human ventricular myocytes from failing and non-failing hearts.
• To compare human I(to) with that of rat myocytes.

Main Methods:

• Whole-cell patch clamp technique was employed to study depolarisation-dependent I(to) in isolated human ventricular myocytes.
• Human myocytes were obtained from heart transplant recipients (failing hearts) and multiorgan donors (non-failing hearts).
• Electrophysiological properties were compared between human and rat myocytes.

Main Results:

• I(to) was present in ventricular myocytes from both failing and non-failing human hearts, with similar current densities.
• Human I(to) exhibited slower activation and faster inactivation kinetics compared to rat I(to).
• The late component of outward current in human cells showed no potential-dependent inactivation, unlike in rat cells.

Conclusions:

• Transient outward currents (I(to)) in human ventricular myocytes do not show dramatic differences between failing and non-failing hearts.
• Human I(to) characteristics are similar, though not identical, to those observed in rat heart cells.
• I(to) represents a potential therapeutic target for antiarrhythmic drug development.