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Effects of propafenone on calcium current in guinea‐pig ventricular myocytes
Author(s) -
Delgado C.,
Tamargo J.,
Henzel D.,
Lorente P.
Publication year - 1993
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.1476-5381.1993.tb12868.x
Subject(s) - propafenone , depolarization , chemistry , electrophysiology , patch clamp , voltage clamp , calcium , pharmacology , biophysics , medicine , biology , atrial fibrillation
1 The modulation of L‐type voltage‐sensitive calcium channels in guinea‐pig isolated ventricular myocytes by propafenone was examined by the whole cell voltage‐clamp technique. 2 Propafenone, 10 −7 −5 × 10 −5 m , produced a concentration‐dependent inhibition of Ca current ( I Ca ) without any significant change in the current‐voltage relation. Half‐blocking concentration (IC 50 ) of propafenone for the peak I Ca at +10 mV was 5 × 10 −6 m . 3 The voltage‐dependence of I Ca inactivation was shifted in the hyperpolarizing direction in the presence of 5 × 10 −6 m propafenone. 4 A frequency‐dependent relative block by propafenone was observed after repetitive depolarizing test pulses at a frequency of 0.5 and 1 Hz. The recovery of I Ca from inactivation was prolonged by propafenone and the reactivation exhibited an additional exponential component attributed to the slow release from drug block of Ca channels. 5 These results suggest that propafenone, at therapeutic concentrations exhibits Ca channel blocking properties that may be involved in its antiarrhythmic mechanism.