A dynamic action potential model analysis of shock-induced aftereffects in ventricular muscle by reversible breakdown of cell membrane.
To elucidate the subcellular mechanism underlying the aftereffects of high-intensity dc shocks, a small pore, which mimics reversible breakdown of the cell membrane (electroporation), was incorporated into the phase-2 Luo-Rudy (L-R) model of ventricular action potentials. The pore size was set to occupy 0.15%-4.25% of the total cell membrane during the 10-ms shock. The pore was assumed to decrease after the shock exponentially with a time constant of 100-1,400 ms to simulate resealing process. In normal myocytes, the pore formation results in a delay of repolarization of the shocked action potential, which is followed by prolonged depolarization and oscillation of membrane potential like early afterdepolarization (EAD). Time- and voltage-dependent changes in the delayed rectifier K+ currents (IKr, IKs) in combination with those of L-type Ca2+ current (ICa,(L)) and ion flux through the pore (I(pore)) are responsible for the potential changes. Spontaneous excitation from the oscillation depends on activation of ICa,(L). In myocytes overloaded with Na+ and Ca2+ secondary to 90% inhibition of Na+-K+ pump, the pore formation results in a delay of repolarization of the shocked action potential, which is followed by slower cyclic depolarization in response to spontaneous release of Ca2+ from the sarcoplasmic reticulum (SR). This delayed afterdepolarization-type oscillation is abolished by complete block of Ca2+ release from the SR. These findings suggest that high-intensity electric field application will cause arrhythmogenic responses through a transient rupture of sarcolemma with different subcellular events in ventricular cells under normal and pathological conditions.
Ohuchi
Katsuhiro
K
Department of Artificial Organs, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Japan. ouchi.ao@tmd.ac.jp
Fukui
Yasuhiro
Y
Sakuma
Ichiro
I
Shibata
Nitaro
N
Honjo
Haruo
H
Kodama
Itsuo
I
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D015220:Calcium Channels / Q000502:physiology; D004553:Electric Conductivity; D004558:Electric Stimulation; D006168:Guinea Pigs; D008564:Membrane Potentials / Q000502:physiology; D015222:Sodium Channels / Q000502:physiology; D016276:Ventricular Function
D015220:Calcium Channels; D015222:Sodium Channels