Modification of contraction by the electrical coupling of individual cardiac myocytes; A model study

Abstract

The dynamic computer simulation is essential for quantitative understanding of integrated mechanisms underlying various cell functions. The two-dimensional models of action potential propagation successfully demonstrated the basic mechanisms of re-entry. However, the gap junction conductance is regulated by, for example, the intracellular Ca²⁺, pH, and protein kinase. Thus, to examine the physiological and pathophysiological conditions, we need to consider many aspects such as intracellular Ca²⁺ homeostasis, energy metabolism, and so on. To evaluate the effect of varying electrical coupling on the electro-mechanical properties of myocytes, we coupled individual ventricular cell model. When the two ventricular cell models were connected with the conductance over 7 nS, the action potential of the 1st cell propagated to the 2nd cell with a clear delay, though the repolarizing phase was almost synchronized. Under this condition, the action potential of the 1st cell showed a marked downward notch after the peak. The amplitude of Ca²⁺ current in the 1st cell was increased during the notch because of larger driving force, so that the Ca²⁺ transient and contraction were increased. Thus, the 1st cell produced a larger contraction than the 2nd one. Increasing the number of coupled cells from 2 to 5, a larger gap junction conductance was needed to propagate the action potential. The dynamic regulation of conductance described in the literature should be applied to the gap junction model. [Jpn J Physiol 54 Suppl:S105 (2004)]