抄録
Computers have become the necessities of life science with improvements of information technologies. Thus, Systems Biology, whose aim is to describe the whole biological interactions as a mathematical model and understand the whole mechanisms by simulation, has been emerged. We have started developing a comprehensive cardiac model (Kyoto model), and a cardiac sinoatrial node pacemaker model is developed with the same set of equations as the ventricular cell model. The model successfully reconstructs the experimental action potentials at various concentrations of external Ca2+ and K+, and reaches steady-state and the sensitivity analyses can be applied to a variety set of parameters. Increasing the amplitude of L-type Ca2+ current (ICaL) prolongs the duration of the action potential and thereby slightly decreases the spontaneous rate. On the other hand, a negative voltage shift of ICaL gating by a few mV markedly increases the spontaneous rate. When the amplitude of sustained inward current is increased, the spontaneous rate is increased irrespective of the ICaL amplitude. When the spontaneous activity is stopped by decreasing ICaL amplitude, the resting potential is around -35 mV over 1-15 mM [K+]o because of the presence of the background non-selective cation current. 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 equilibrium potential during the course of the spontaneous activity. [J Physiol Sci. 2006;56 Suppl:S55]
