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A novel anionic conductance affects action potential duration in isolated rat ventricular myocytes
C I Spencer1, W Uchida, R Z Kozlowski
1Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, U.K.
British Journal of Pharmacology
|February 29, 2000
Summary
Researchers identified a novel anionic background current (I(AB)) in rat ventricular myocytes that significantly influences action potential duration (APD). This discovery offers new insights into cardiac ion channels and potential antiarrhythmic drug targets.
Area of Science:
- Cardiology
- Electrophysiology
- Ion Channel Physiology
Background:
- Extracellular anions play a crucial role in cardiac electrophysiology.
- Understanding ion channel function is key to developing antiarrhythmic therapies.
Purpose of the Study:
- To investigate the effects of extracellular anions on rat ventricular myocytes.
- To characterize a novel anionic background current (I(AB)) and its role in action potential duration (APD).
Main Methods:
- Electrophysiological experiments (current-clamp and voltage-clamp) on isolated rat ventricular myocytes.
- Anion substitution experiments using various extracellular anions (Cl(-), Br(-), I(-), NO(3)(-)).
- Assessment of I(AB) properties, including Ca(2+)/cAMP independence and insensitivity to common blockers.
Main Results:
- Reducing extracellular Cl(-) prolonged APD; replacing Cl(-) with I(-) shortened APD.
- A Ca(2+)- and cyclic AMP-independent anionic background current (I(AB)) was identified.
- I(AB) was insensitive to stilbene and fenamate blockers, suggesting a novel channel type.
- I(AB) significantly correlates with rat ventricular APD control.
Conclusions:
- Rat ventricular myocytes possess a novel class of anion channel mediating I(AB).
- This I(AB) plays a significant role in regulating cardiac action potential duration.
- These findings highlight potential new targets for antiarrhythmic drug development.