Zusammenfassung
The action potential model presented in our accompanying article in
this journal is used to investigate phenomena that involve dynamic
changes of Ca$^2+$i, as described below. Delayed afterdepolarizations
(DADs) are induced by spontaneous Ca$^2+$ release from the sarcoplasmic
reticulum (SR), which, in turn, activates both the Na$^+$-Ca$^2+$
exchanger (INaCa) and a nonspecific Ca$^2+$-activated current
(Ins(Ca)). The relative contributions of INaCa and of Ins(Ca) to
the generation of DADs are different under different degrees of Ca$^2+$
overload. Early afterdepolarizations (EADs) can be categorized into
two types: (1) plateau EADs, resulting from a secondary activation
of the L-type Ca$^2+$ current during the plateau of an action
potential, and (2) phase-3 EADs, resulting from activation of INaCa
and Ins(Ca) by increased Ca$^2+$i due to spontaneous Ca$^2+$
release from the SR during the late repolarization phase. Spontaneous
rhythmic activity and triggered activity are caused by spontaneous
Ca$^2+$ release from the SR under conditions of Ca$^2+$ overload.
Postextrasystolic potentiation reflects the time delay associated
with translocation of Ca$^2+$ from network SR to junctional SR.
The cell is paced at high frequencies to investigate the long-term
effects on the intracellular ionic concentrations.
- 7514510
- action
- animals,
- biological,
- calcium,
- channels,
- gov't,
- guinea
- heart,
- ion
- models,
- non-u.s.
- p.h.s.,
- pigs,
- potentials,
- research
- support,
- u.s.
Nutzer