Action Potential Duration Restitution and Alternans in Rabbit Ventricular Myocytes

Abstract

Abstract-Action potential duration (APD) restitution properties and repolarization alternans are thought to be important arrhythmogenic factors. We investigated the role of intracellular calcium (Ca 2ϩ i ) cycling in regulating APD restitution slope and repolarization (APD) alternans in patch-clamped rabbit ventricular myocytes at 34 to 36°C, using the perforated or ruptured patch clamp techniques with Fura-2-AM to record Ca 2ϩ i . When APD restitution was measured by either the standard extrastimulus (S1S2) method or the dynamic rapid pacing method, the maximum APD restitution slope exceeded 1 by both methods, but was more shallow with the dynamic method. These differences were associated with greater Ca 2ϩ i accumulation during dynamic pacing. The onset of APD alternans occurred at diastolic intervals at which the APD restitution slope was significantly Ͻ1 and was abolished by suppressing sarcoplasmic reticulum (SR) Ca

Ethanol Extract ofLycopus lucidusElicits Positive Inotropic Effect Via Activation of Ca2+Entry and Ca2+Release in Beating Rabbit Atria

“…22 Also, depolarization-induced increase in intracellular Ca 2 + was inhibited by combined treatment with ryanodine and thapsigargin in rabbit ventricular myocytes. 23 Further, the finding showing that L-type Ca 2 + channel inhibitors suppress the ELT-induced positive inotropic effects indicates that Ca 2 + entry is also involved in this effect. Therefore, these results suggest that ELT increased atrial dynamics via activation of Ca 2 + entry through L-type Ca 2 + channels and Ca 2 + release from the SR (Fig.…”

“…Combined treatment with ryanodine and thapsigargin fully suppresses SR Ca 2 + cycling and elevation of intracellular Ca 2 + induced by stimulation in canine sinoatrial node and rabbit ventricular myocytes. 22,23 It has been known that the combined treatment with ryanodine and thapsigargin inhibits isoproterenol-induced increase in intracellular Ca 2 + levels in the Langendorff-perfused canine sinoatrial node. 22 Also, depolarization-induced increase in intracellular Ca 2 + was inhibited by combined treatment with ryanodine and thapsigargin in rabbit ventricular myocytes.…”

Nonlinear physics of electrical wave propagation in the heart: a review

“…This is known as the restitution hypothesis [228]. However, there is contradictory evidence regarding its validity [229,230]. In effect, various authors reported severe shortcomings of the mentioned criteria [231,232].…”

Characterization of the cardiac sodium channel SCN5A mutation, N1325S, in single murine ventricular myocytes

“…Representative I Na traces (no. 1,10,15,20,25) elicited by the test pulse are illustrated in Fig. 3B and reflects this depolarizing shift in half-inactivation (increased I Na availability) for TS-NS/LQT3 cells since peak I Na at trace 1 and 10 are comparable in amplitude.…”

“…3,Table 1) led us to speculate that the generation and/or maintenance of AP prolongation were largely due to some instability in [Ca 2+ ] i ions. Beat-to-beat variability of repolarization and abnormalities in [Ca 2+ ] i in cardiomyocytes has been recognized [13][14][15][16]. As shown in Fig.…”