23 research outputs found
Contribution of L-Type Ca2+ Channels to Early Afterdepolarizations Induced by I Kr and I Ks Channel Suppression in Guinea Pig Ventricular Myocytes
Triamterene inhibits the delayed rectifier potassium current (IK) in guinea pig ventricular myocytes.
Droperidol Lengthens Cardiac Repolarization due to Block of the Rapid Component of the Delayed Rectifier Potassium Current
Pharmacological Enhancement of Cardiac Gap Junction Coupling Prevents Arrhythmias in Canine LQT2 Model
Comparison of the effect of class IA antiarrhythmic drugs on transmembrane potassium currents in rabbit ventricular myocytes
BACKGROUND:
The blockade of cardiac transmembrane potassium channels, which is commonly seen with various antiarrhythmic drugs, plays an important role in their mechanism of action. We studied and compared the less-explored effects of three Class IA antiarrhythmics on the transient outward current (I(to)) and on the inward rectifier (I(kl)), ATP sensitive (I(KATP)), and delayed rectifier (I(K)) potassium currents in rabbit ventricular myocytes.
METHODS AND RESULTS:
Transmembrane currents were measured by applying the whole-cell configuration of the patch-clamp technique at 37 degrees C in myocytes enzymatically isolated from rabbit ventricular preparations. Quinidine (10 microM), disopyramide (10 microM), and procainamide (50 microM) were studied at concentrations close to or exceeding the therapeutic plasma level. All studied drugs significantly decreased the amplitude of I(KATP) (activated by 50 microM pinacidil) and I(K) currents. None of them influenced significantly I(kl). The amplitude of I(to) was decreased by quinidine and disopyramide but was not considerably altered by procainamide. The fast inactivation of I(to) was not changed by procainamide and was significantly accelerated by quinidine and disopyramide.
CONCLUSION:
Although quinidine, disopyramide, and procainamide are all classified as Class IA antiarrhythmics, these drugs had different effects on various potassium currents, which may partially explain their distinct effect on repolarization in various cardiac tissues and on cardiac arrhythmias in clinical settings