Excitation-contraction coupling in heart muscle

W. J. Lederer, M. B. Cannell, N. M. Cohen, J. R. Berlin

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

We have investigated the links between electrical excitation and contraction in mammalian heart muscle. Using isolated single cells from adult rat ventricle, a whole-cell voltage-clamp technique and quantitative fluorescence microscopy, we have measured simultaneously calcium current (Ica) and [Ca2+]i (with fura-2). We find that the voltage-dependence of Ica and the [Ca 2+]i-transient and the dependence of [Ca2+]i-transient on depolarization-duration cannot both be readily explained by a simple calcium-induced Ca-release ('CICR') mechanism. Additionally, we find that when [Ca2+]i and [Na+]i are at their diastolic levels, activation of the Na-Ca exchange mechanism by depolarization does not measurably trigger the release of Ca2+i. Finally, measuring Ica in adult and neonatal rat heart cells and using the alkaloid ryanodine, we have carried out complementary experiments. These experiments show that there may be an action of ryanodine on Ica that is independent of [Ca2+]i and independent of a direct action of the alkaloid on the calcium channel itself. Along with experiments of others showing that ryanodine binds to the sarcoplasmic reticulum calcium-release channel/spanning protein complex, our data suggests a model to explain our findings. The model links the calcium channels responsible for Ica to the sarcoplasmic reticulum by means of one or more of the spanning protein(s). Information from the calcium channel can be communitated to the sarcoplasmic reticulum by this route and, presumably, information can move in the opposite direction from the sarcoplasmic reticulum to the calcium channel.

Original languageEnglish (US)
Pages (from-to)115-119
Number of pages5
JournalMolecular and cellular biochemistry
Volume89
Issue number2
DOIs
StatePublished - Sep 1 1989
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Clinical Biochemistry
  • Cell Biology

Keywords

  • calcium current
  • excitation-contraction coupling
  • fura-2
  • intracellular calcium
  • mammalian heart muscle
  • sodium-calcium exchange

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