Premium
Increase in action potential duration and inhibition of the delayed rectifier outward current I K by berberine in cat ventricular myocytes
Author(s) -
SánchezChapula José
Publication year - 1996
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1996.tb15302.x
Subject(s) - berberine , inward rectifier potassium ion channel , chemistry , potassium channel blocker , anti arrhythmia agents , pharmacology , depolarization , potassium channel , myocyte , patch clamp , medicine , electrophysiology , endocrinology , ion channel , biochemistry , receptor , atrial fibrillation
1 In the present work, the effects of the antiarrhythmic drug, berberine, on action potential and ionic currents of cat ventricular myocytes were studied. 2 Berberine prolonged action potential duration in cat ventricular myocytes without altering other variables of the action potential. 3 The drug at concentrations of 0.3–30 μ blocked only the delayed rectifier ( I K ) current with an IC 50 = 4.1 μ. Berberine produced a tonic block and a phasic block that was increased with the duration of the depolarizing pulse. The blocking effect on I K was use‐dependent, but not frequency‐dependent. 4 In cardiac preparations two delayed rectifier currents have been found: a rapid ( I K ) current and a slow ( I K ) current. In the present work it has been found that berberine at the concentrations used, selectively blocked I Kr . 5 At concentrations higher than 10 μ it also decreased the transient outward ( I to1 ) current. The drug did not have effects on the inward rectifier ( I K1 ) or the high threshold calcium current ( I Ca‐L ). 6 These results show that berberine is a specific potassium channel blocker. The increase in action potential duration induced by berberine can be explained mainly by its blocking effects on I K .