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Modulation of the cardiac transient outward current by catecholamines
T Nakayama1, C Palfrey, H A Fozzard
1Department of Medicine, University of Chicago, IL 60637.
Journal of Molecular and Cellular Cardiology
|February 1, 1989
Summary
Norepinephrine modulates cardiac transient outward current by altering inactivation kinetics, suggesting neurotransmitter regulation via cAMP-dependent protein kinase. This impacts cardiac cell electrical activity.
Area of Science:
- Cardiovascular Physiology
- Molecular Cardiology
- Ion Channel Function
Background:
- The transient outward current (Ito) is crucial for cardiac action potential repolarization.
- Understanding its regulation by neurotransmitters is vital for cardiac electrophysiology.
Purpose of the Study:
- To investigate the effects of norepinephrine and isoproterenol on the transient outward current in canine Purkinje cells.
- To elucidate the underlying signaling pathway involved in this modulation.
Main Methods:
- Voltage clamp technique on single canine Purkinje cells under calcium-free conditions.
- Application of norepinephrine, isoproterenol, forskolin, and sotalol.
- Intracellular perfusion with cAMP-dependent protein kinase catalytic subunit.
Main Results:
- Norepinephrine and isoproterenol altered inactivation kinetics of the transient outward current without affecting activation.
- These catecholamines reduced the fast inactivation component and increased the slow component amplitude.
- The effects were mimicked by forskolin and increased cAMP, and blocked by sotalol, implicating cAMP-dependent protein kinase.
Conclusions:
- Neurotransmitters like norepinephrine can modulate cardiac transient outward current kinetics.
- This modulation likely occurs through a pathway involving cAMP and protein kinase A.
- Suggests a role for neurotransmitter regulation of cardiac ion channels potentially via phosphorylation.