The nature of the external ionic modulation of the myocardial electrical propagation

Importance of the safety factor

Toru Maruyama, J. Ejima, Y. Kaji, Y. Tsuda, S. Kanaya, T. Fujino

Research output: Contribution to journalArticle

Abstract

The mechanisms of conduction change depending on the extracellular K+ and Ca2+ concentrations ([K+](o) and [Ca2+](o), respectively) were investigated. Simultaneous measurements of active and passive membrane properties and net membrane excitability were fulfilled by arranging the intra- and extracellular microelectrodes in a superfused and paced guinea pig papillary muscle. Internal longitudinal resistance (r(i)), as a parameter of passive property, was evaluated by the intra- and extracellular voltage ratio. The maximum upstroke rate (V̇(max)) was used as an active property. Apparent threshold potential (V(th)) was defined by the breakpoint in the action potential upstroke fitted semilogarithmically. Graded rise in [K+](o) (from 2.7 to 15.0 mM) evoked a progressive fall in V̇(max), and was associated with less negative resting membrane potential and constant r(i). Conduction velocity (Θ) was the maximum in 9.0 mM [K+](o) ('supernormal' conduction) but not in 2.7 mM [K+](o) which gave the greatest V̇(max) ('subnormal' conduction). Safety factor of conduction (S), as an index of net excitability, could most readily account for the [K+](o)-dependent change in Θ. This was true also in the case of [Ca2+](o) elevation (from 0.9 to 5.4 mM). These results indicate that the cation-modulated propagation is governed by the cable theory including S as a matrix of combined active and passive properties.

Original languageEnglish
Pages (from-to)415-424
Number of pages10
JournalJournal of the Physiological Society of Japan
Volume56
Issue number12
Publication statusPublished - Dec 1 1994

Fingerprint

Safety
Membranes
Papillary Muscles
Microelectrodes
Membrane Potentials
Action Potentials
Cations
Guinea Pigs

All Science Journal Classification (ASJC) codes

  • Medicine(all)

Cite this

The nature of the external ionic modulation of the myocardial electrical propagation : Importance of the safety factor. / Maruyama, Toru; Ejima, J.; Kaji, Y.; Tsuda, Y.; Kanaya, S.; Fujino, T.

In: Journal of the Physiological Society of Japan, Vol. 56, No. 12, 01.12.1994, p. 415-424.

Research output: Contribution to journalArticle

@article{b48070e7e3b14d12880039f8cc8ee108,
title = "The nature of the external ionic modulation of the myocardial electrical propagation: Importance of the safety factor",
abstract = "The mechanisms of conduction change depending on the extracellular K+ and Ca2+ concentrations ([K+](o) and [Ca2+](o), respectively) were investigated. Simultaneous measurements of active and passive membrane properties and net membrane excitability were fulfilled by arranging the intra- and extracellular microelectrodes in a superfused and paced guinea pig papillary muscle. Internal longitudinal resistance (r(i)), as a parameter of passive property, was evaluated by the intra- and extracellular voltage ratio. The maximum upstroke rate (V̇(max)) was used as an active property. Apparent threshold potential (V(th)) was defined by the breakpoint in the action potential upstroke fitted semilogarithmically. Graded rise in [K+](o) (from 2.7 to 15.0 mM) evoked a progressive fall in V̇(max), and was associated with less negative resting membrane potential and constant r(i). Conduction velocity (Θ) was the maximum in 9.0 mM [K+](o) ('supernormal' conduction) but not in 2.7 mM [K+](o) which gave the greatest V̇(max) ('subnormal' conduction). Safety factor of conduction (S), as an index of net excitability, could most readily account for the [K+](o)-dependent change in Θ. This was true also in the case of [Ca2+](o) elevation (from 0.9 to 5.4 mM). These results indicate that the cation-modulated propagation is governed by the cable theory including S as a matrix of combined active and passive properties.",
author = "Toru Maruyama and J. Ejima and Y. Kaji and Y. Tsuda and S. Kanaya and T. Fujino",
year = "1994",
month = "12",
day = "1",
language = "English",
volume = "56",
pages = "415--424",
journal = "Nippon seirigaku zasshi. Journal of the Physiological Society of Japan",
issn = "0031-9341",
publisher = "Physiological Society of Japan",
number = "12",

}

TY - JOUR

T1 - The nature of the external ionic modulation of the myocardial electrical propagation

T2 - Importance of the safety factor

AU - Maruyama, Toru

AU - Ejima, J.

AU - Kaji, Y.

AU - Tsuda, Y.

AU - Kanaya, S.

AU - Fujino, T.

PY - 1994/12/1

Y1 - 1994/12/1

N2 - The mechanisms of conduction change depending on the extracellular K+ and Ca2+ concentrations ([K+](o) and [Ca2+](o), respectively) were investigated. Simultaneous measurements of active and passive membrane properties and net membrane excitability were fulfilled by arranging the intra- and extracellular microelectrodes in a superfused and paced guinea pig papillary muscle. Internal longitudinal resistance (r(i)), as a parameter of passive property, was evaluated by the intra- and extracellular voltage ratio. The maximum upstroke rate (V̇(max)) was used as an active property. Apparent threshold potential (V(th)) was defined by the breakpoint in the action potential upstroke fitted semilogarithmically. Graded rise in [K+](o) (from 2.7 to 15.0 mM) evoked a progressive fall in V̇(max), and was associated with less negative resting membrane potential and constant r(i). Conduction velocity (Θ) was the maximum in 9.0 mM [K+](o) ('supernormal' conduction) but not in 2.7 mM [K+](o) which gave the greatest V̇(max) ('subnormal' conduction). Safety factor of conduction (S), as an index of net excitability, could most readily account for the [K+](o)-dependent change in Θ. This was true also in the case of [Ca2+](o) elevation (from 0.9 to 5.4 mM). These results indicate that the cation-modulated propagation is governed by the cable theory including S as a matrix of combined active and passive properties.

AB - The mechanisms of conduction change depending on the extracellular K+ and Ca2+ concentrations ([K+](o) and [Ca2+](o), respectively) were investigated. Simultaneous measurements of active and passive membrane properties and net membrane excitability were fulfilled by arranging the intra- and extracellular microelectrodes in a superfused and paced guinea pig papillary muscle. Internal longitudinal resistance (r(i)), as a parameter of passive property, was evaluated by the intra- and extracellular voltage ratio. The maximum upstroke rate (V̇(max)) was used as an active property. Apparent threshold potential (V(th)) was defined by the breakpoint in the action potential upstroke fitted semilogarithmically. Graded rise in [K+](o) (from 2.7 to 15.0 mM) evoked a progressive fall in V̇(max), and was associated with less negative resting membrane potential and constant r(i). Conduction velocity (Θ) was the maximum in 9.0 mM [K+](o) ('supernormal' conduction) but not in 2.7 mM [K+](o) which gave the greatest V̇(max) ('subnormal' conduction). Safety factor of conduction (S), as an index of net excitability, could most readily account for the [K+](o)-dependent change in Θ. This was true also in the case of [Ca2+](o) elevation (from 0.9 to 5.4 mM). These results indicate that the cation-modulated propagation is governed by the cable theory including S as a matrix of combined active and passive properties.

UR - http://www.scopus.com/inward/record.url?scp=0028556626&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0028556626&partnerID=8YFLogxK

M3 - Article

VL - 56

SP - 415

EP - 424

JO - Nippon seirigaku zasshi. Journal of the Physiological Society of Japan

JF - Nippon seirigaku zasshi. Journal of the Physiological Society of Japan

SN - 0031-9341

IS - 12

ER -