Zusammenfassung
Mathematical models were developed to reconstruct the action potentials
(AP) recorded in epicardial and endocardial myocytes isolated from
the adult rat left ventricle. The main goal was to obtain additional
insight into the ionic mechanisms responsible for the transmural
AP heterogeneity. The simulation results support the hypothesis that
the smaller density and the slower reactivation kinetics of the Ca$^2+$-independent
transient outward K$^+$ current (I(t)) in the endocardial myocytes
can account for the longer action potential duration (APD), and
more prominent rate dependence in that cell type. The larger density
of the Na$^+$ current (I(Na)) in the endocardial myocytes results
in a faster upstroke (dV/dt(max)). This, in addition to the smaller
magnitude of I(t), is responsible for the larger peak overshoot of
the simulated endocardial AP. The prolonged APD in the endocardial
cell also leads to an enhanced amplitude of the sustained K$^+$
current (I(ss)), and a larger influx of Ca$^2+$ ions via the
L-type Ca$^2+$ current (I(CaL)). The latter results in an increased
sarcoplasmic reticulum (SR) load, which is mainly responsible for
the higher peak systolic value of the Ca$^2+$ transient Ca$^2+$(i),
and the resultant increase in the Na$^+$-Ca$^2+$ exchanger
(I(NaCa)) activity, associated with the simulated endocardial AP.
In combination, these calculations provide novel, quantitative insights
into the repolarization process and its naturally occurring transmural
variations in the rat left ventricle.
- 11720973
- action
- anima,
- calcium
- calcium,
- channels,
- electrophysiology,
- endocardium,
- factors,
- gov't,
- heart
- ions,
- l-type,
- ls,
- models,
- myocardium,
- non-u.s.
- pericardium,
- potassium,
- potentials,
- rats,
- research
- sarcolemma,
- sodium
- sodium,
- support,
- theoretical,
- time
- ventricles,
Nutzer