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Effects of propafenone on calcium currents in single ventricular myocytes of guinea‐pig
Author(s) -
Fei Lü,
Gill Jaswinder S.,
McKenna William J.,
Camm A. John
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.tb13550.x
Subject(s) - propafenone , medicine , stimulation , chemistry , calcium , pharmacology , atrial fibrillation
1 The effects of propafenone on the inward calcium current ( I Ca ) were investigated in isolated single ventricular myocytes of the guinea‐pig by the whole‐cell clamp method. Propafenone inhibited I Ca in a dose‐dependent manner at concentrations of propafenone ranging from 1 × 10 −8 to 1 × 10 −3 m and half maximal block of I Ca occurred at a propafenone concentration of 1.5 × 10 −6 m . Propafenone did not change the current‐voltage relation of I Ca other than a reduction in amplitude and showed no clear use‐ or frequency‐dependent effects upon I Ca (stimulation frequencies from 0.03 to 2 Hz). Propafenone did not alter the steady‐state inactivation process: the half maximal activation potentials were 18.5 ± 2.2 mV in the control state and 20.9 ± 5.0 mV in the presence of 1×10 −6 m propafenone ( n = 12, NS). Propafenone (1 × 10 −6 m ) increased the half‐time of reactivation by 73.9% ( n = 6, 212.3 ± 1.2 ms vs 369.2 ± 1.5 ms, P < 0.05). 2 We conclude that propafenone blocks I Ca in a concentration‐dependent and a channel state‐, use‐ or frequency‐independent manner. The I Ca , blockade elicited by propafenone at clinically therapeutic plasma concentration is significant and may be involved in its anti‐arrhythmic effects.