Effects of propafenone on calcium current in guinea‐pig ventricular myocytes
Why the study?
Does propafenone inhibit L-type calcium currents in guinea-pig ventricular myocytes?
Population
Guinea-pig isolated ventricular myocytes
Comparison
Propafenone (10^-7 to 5 x 10^-5 M) vs Control/baseline (absence of propafenone)
Design
Preclinical
Authors
Discussion
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Implication
Supports calcium channel blockade as a propafenone antiarrhythmic mechanism; hypothesis-generating and requires human validation.
Key Points
- To examine the effects and electrophysiological mechanisms of propafenone on L-type voltage-sensitive calcium currents in isolated ventricular heart cells.
- Applied the whole-cell voltage-clamp technique to isolated guinea-pig ventricular myocytes.
- Tested propafenone concentrations ranging from 10⁻⁷ M to 5 × 10⁻⁵ M across varying stimulation frequencies (0.5 and 1 Hz) and membrane potentials.
- Propafenone produced a concentration-dependent inhibition of calcium current (ICa) with an IC50 of 5 × 10⁻⁶ M at +10 mV without changing the current-voltage relationship.
- Propafenone at 5 × 10⁻⁶ M shifted the voltage-dependence of ICa inactivation in the hyperpolarizing direction.
- Frequency-dependent block was observed at 0.5 and 1 Hz, and propafenone prolonged ICa recovery with a slow exponential reactivation component.
Structured PICO
Does propafenone inhibit L-type calcium currents in guinea-pig ventricular myocytes?
P
Population
Guinea-pig isolated ventricular myocytes
I
Intervention
Propafenone (10^-7 to 5 x 10^-5 M)
C
Comparator
Control/baseline (absence of propafenone)
O
Outcome
Modulation of L-type voltage-sensitive calcium channels (Ca current, ICa)surrogate
Propafenone exhibits calcium channel blocking properties at therapeutic concentrations, which may contribute to its antiarrhythmic mechanism.
Cite This Study
Delgado et al. (1993) studied this question.