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Role of individual ionic current systems in the SA node hypothesized by a model study.

Nobuaki Sarai·Satoshi Matsuoka·Shinobu Kuratomi·Kyoichi Ono·Akinori Noma
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Abstract

This paper discusses the development of a cardiac sinoatrial (SA) node pacemaker model. The model successfully reconstructs the experimental action potentials at various concentrations of external Ca2+ and K+. Increasing the amplitude of L-type Ca2+ current (I(CaL)) prolongs the duration of the action potential and thereby slightly decreases the spontaneous rate. On the other hand, a negative voltage shift of I(CaL) gating by a few mV markedly increases the spontaneous rate. When the amplitude of sustained inward current (I(st)) is increased, the spontaneous rate is increased irrespective of the I(CaL) amplitude. Increasing [Ca2+](o) shortens the action potential and increases the spontaneous rate. When the spontaneous activity is stopped by decreasing I(CaL) amplitude, the resting potential is nearly constant (-35 mV) over 1-15 mM [K+](o) as observed in the experiment. This is because the conductance of the inward background non-selective cation current balances with the outward [K+](o)-dependent K+ conductance. The unique role of individual voltage- and time-dependent ion channels is clearly demonstrated and distinguished from that of the background current by calculating an instantaneous zero current potential ("lead potential") during the course of the spontaneous activity.

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Action PotentialsAlgorithmsAnimalsBiological ClocksCalciumCalcium ChannelsCalcium Channels, L-TypeComputer SimulationDiastoleGuinea PigsIon ChannelsIon TransportIonsMembrane PotentialsModels, BiologicalMyocytes, CardiacPotassiumSinoatrial NodeComparative StudyJournal ArticleResearch Support, Non-U.S. Gov't

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Nobuaki Sarai, Satoshi Matsuoka, Shinobu Kuratomi, Kyoichi Ono, Akinori Noma. 2003. Role of individual ionic current systems in the SA node hypothesized by a model study.. https://doi.org/10.2170/jjphysiol.53.125

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