Kinetics of [Ca](i) decline in cardiac myocytes depend on peak [Ca](i)

D. M. Bers, J. R. Berlin

Research output: Contribution to journalArticle

127 Citations (Scopus)

Abstract

The rate of decline of free intracellular Ca concentration ([Ca](i)) is a potentially useful index of the function of Ca transport systems. However, interpretations of these results may depend on multiple Ca transport systems and interaction with intracellular Ca binding sites. We measured [Ca](i) in voltage-clamped ventricular myocytes isolated from rat hearts using indo 1 fluorescence. Conditions were chosen where [Ca](i) decline was expected to depend almost exclusively on the sarcoplasmic reticulum Ca pump. The half time of [Ca](i) decline (t( 1/2 )) decreased as the amplitude of the intracellular Ca (Ca(i)) transient increased. This is not the result that would be expected from a transport system where the transport rate is a linear function of free [Ca](i). In this case the time constant of [Ca](i) decline (τ) should be independent of the peak value of [Ca](i). This is also true if linear buffering of Ca(i) is included. We develop a simple but more realistic theoretical framework where Ca transport rate and Ca binding both depend on free [Ca](i) with Michaelis-Menten type functions. We demonstrate that the observed decline in apparent 7 with increasing peak [Ca](i) is entirely expected on theoretical grounds and over a wide range of characteristics for Ca transport and binding. We conclude that one cannot draw inferences about the intrinsic Ca transport function based on τ values unless the Ca(i) transient has a comparable size.

Original languageEnglish (US)
Pages (from-to)C271-C277
JournalAmerican Journal of Physiology - Cell Physiology
Volume268
Issue number1 37-1
StatePublished - Jan 1 1995

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sarcoplasmic reticulum
Cardiac Myocytes
pumps
myocytes
binding sites
heart
fluorescence
kinetics
Kinetics
rats
Sarcoplasmic Reticulum
Muscle Cells
Fluorescence
Binding Sites
Rats
Pumps
cardiomyocytes
Electric potential
indo-1

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cell Biology

Cite this

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abstract = "The rate of decline of free intracellular Ca concentration ([Ca](i)) is a potentially useful index of the function of Ca transport systems. However, interpretations of these results may depend on multiple Ca transport systems and interaction with intracellular Ca binding sites. We measured [Ca](i) in voltage-clamped ventricular myocytes isolated from rat hearts using indo 1 fluorescence. Conditions were chosen where [Ca](i) decline was expected to depend almost exclusively on the sarcoplasmic reticulum Ca pump. The half time of [Ca](i) decline (t( 1/2 )) decreased as the amplitude of the intracellular Ca (Ca(i)) transient increased. This is not the result that would be expected from a transport system where the transport rate is a linear function of free [Ca](i). In this case the time constant of [Ca](i) decline (τ) should be independent of the peak value of [Ca](i). This is also true if linear buffering of Ca(i) is included. We develop a simple but more realistic theoretical framework where Ca transport rate and Ca binding both depend on free [Ca](i) with Michaelis-Menten type functions. We demonstrate that the observed decline in apparent 7 with increasing peak [Ca](i) is entirely expected on theoretical grounds and over a wide range of characteristics for Ca transport and binding. We conclude that one cannot draw inferences about the intrinsic Ca transport function based on τ values unless the Ca(i) transient has a comparable size.",
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Kinetics of [Ca](i) decline in cardiac myocytes depend on peak [Ca](i). / Bers, D. M.; Berlin, J. R.

In: American Journal of Physiology - Cell Physiology, Vol. 268, No. 1 37-1, 01.01.1995, p. C271-C277.

Research output: Contribution to journalArticle

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