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Analysis and modeling of na current in cardiac muscles

Memoirs of the Faculty of Engineering, Yamaguchi University Volume 44 Issue 1 Page 151-158
published_at 1993-10
KJ00000156958.pdf
[fulltext] 698 KB
Title
心筋Na電流の解析とそのモデル化
Analysis and modeling of na current in cardiac muscles
Creators Sada Hideaki
Creators Tanaka Kotaro
Creators Ebina Yoshio
Creators Ban Takashi
Source Identifiers
The (Na)^+ channel plays essential roles in initiation and conduction of action potential in a variety of excitable tissues including nerves, hearts and muscles. Na channels undergo activation and inactivation depending on the membrane voltage and time. Hodgkin & Huxley (H-H), early in 1950s, proposed a mathematical model to describe Na channel properties of the squid axonal membrane, based on voltage-clamp (V-C) study. For the next 3 decades since then, direct recording of the Na current by V-C method and hence the study of Na channel property have been hampered in cardiac tissues largely by the complicated geometry of the tissue. Recent electrophysiological studies using V-C method with patch-pipettes on dispersed single heart cells have demonstrated that the gating-kinetics of Na channels is much more complicated than predicted from the H-H model. To establish a new model which enables describing Na channel events in heart, we conducted V-C study in embryonic chick heart cells. In this preparation, we found pronounced differences in the inactivation and re-inactivation mechanisms from those in the axon, suggesting a presence of one conductive and two inactivated states among which voltage-dependent transitions were permitted (a cyclic reaction model). According to the model, we experimentally determined rate-constants of the reaction. We also found a delay in onset of inactivation as well as activation in voltage-clamped heart cells, and derived empirical equations for such delays in onset. Taken above together, we could faithfully reproduce the Na channel currents observed in heart cells under V-C conditions.
Languages jpn
Resource Type departmental bulletin paper
Publishers 山口大学工学部
Date Issued 1993-10
File Version Version of Record
Access Rights open access
Relations
[ISSN]0372-7661
[NCID]AN00244228
Schools 工学部