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Quinidine interactions with human atrial potassium channels: developmental aspects
N I Nenov1, W J Crumb, J D Pigott
1Departments of Pharmacology, Pediatrics and Surgery, Tulane University School of Medicine, Louisiana State University School of Medicine New Orleans, Louisiana, USA.
Circulation Research
|December 16, 1998
Summary
Quinidine is less effective in pediatric patients due to age-related changes in its interaction with cardiac potassium channels, specifically Ito. This study clarifies age-dependent effects on antiarrhythmic drug action.
Area of Science:
- Cardiology
- Pharmacology
- Electrophysiology
Background:
- Clinical studies indicate reduced quinidine effectiveness for pediatric atrial arrhythmias compared to adults.
- Age-related alterations in quinidine's cardiac effects and potassium channel interactions are documented in mammals.
Purpose of the Study:
- To investigate postnatal developmental effects on quinidine's interaction with major repolarizing currents (Ito, IKur, Ins, IK1) in human atrial myocytes.
- To elucidate the electrophysiological basis for age-dependent quinidine efficacy in treating arrhythmias.
Main Methods:
- Utilized the whole-cell voltage-clamp technique on human atrial myocytes.
- Examined quinidine's blockade and unblocking mechanisms on Ito, IKur, Ins, and IK1 currents.
Main Results:
- Identified age-related changes in quinidine's IC50 for Ito blockade and its unblocking kinetics.
- Demonstrated age-independent inhibition of IK1 and IKur by quinidine.
- Found that the nonselective cation current (Ins) is insensitive to quinidine.
Conclusions:
- Age-dependent modulation of Ito is a key factor in quinidine's variable efficacy between pediatric and adult patients.
- Quinidine's effects on IK1 and IKur are consistent across age groups.
- These findings clarify the electrophysiological mechanisms underlying quinidine's antiarrhythmic action in different populations.