Application of uniform-field shocks to cultured cardiac cell strands caused passive changes of transmembrane potential followed by two voltage- and time-dependent shifts.
Defibrillation shocks applied to cultured myocyte strands induce complex, non-linear, time- and voltage-dependent shifts in transmembrane potential, likely reflecting ionic current changes or electroporation.
Organization of cardiac tissue into cell strands and layers has been implicated in changes of transmembrane potential (DeltaV(m)) during defibrillation. To determine the shock-induced DeltaV(m) in such structures, cell strands of variable width strand width (SW) = 0.15-2 mm were grown in culture. Uniform-field shocks with variable strength shock strength (SS) = 2-50 V/cm were applied across strands during the action potential (AP) plateau, and DeltaV(m) were measured optically. Three different types of DeltaV(m) were observed. Small DeltaV(m) [ positive DeltaV(m) because of a negative time-dependent shift of V(m) at the depolarized side of the strands. For large DeltaV(m) (>200%APA), a second time-dependent shift of V(m) to more positive levels was observed in the hyperpolarized portions of strands, causing reduction of the DeltaV(m) asymmetry. We conclude that during application of shocks to cell strands during the AP plateau, passive changes of V(m) were followed by two voltage- and time-dependent shifts of V(m), possibly reflecting changes of ionic currents or membrane electroporation.
Fast et al. (Wed,) conducted a other in Cultured cardiac myocytes. Uniform-field shocks was evaluated on Changes of transmembrane potential (DeltaV(m)). Application of uniform-field shocks to cultured cardiac cell strands caused passive changes of transmembrane potential followed by two voltage- and time-dependent shifts.
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