Modulation of excitation-contraction coupling by isoproterenol in cardiomyocytes with controlled SR Ca2+ load and Ca2+ current trigger

Kenneth S Ginsburg, Donald M Bers

Research output: Contribution to journalArticle

128 Citations (Scopus)

Abstract

Cardiac Ca2+ transients are enhanced by cAMP-dependent protein kinase (PKA). However, PKA-dependent modulation of ryanodine receptor (RyR) function in intact cells is difficult to measure, because PKA simultaneously increases Ca2+ current (ICa), SR Ca2+ uptake and SR Ca2+ loading (which independently increase SR Ca2+ release). We measured ICa and SR Ca2+ release ± 1 μm isoproterenol (ISO; isoprenaline) in voltage-clamped ventricular myocytes of rabbits and transgenic mice (expressing only non-phosphorylatable phospholamban). This mouse model helps control for any effect of ISO-enhanced SR uptake on observed release, but the two species produced essentially identical results. SR Ca2+ load and ICa were adjusted by conditioning. We thus evaluated PKA effects on SR Ca2+ release at constant SR Ca2+ load and ICa trigger (with constant unitary ICa). The amount of SR Ca2+ release increased as a function of either ICa or SR Ca2+ load, but ISO did not alter the relationships (measured as gain or fractional release). This was true over a wide range of SR Ca2+ load and ICa. However, the maximal rate of SR Ca2+ release was ∼50% faster with ISO (at most loads and ICa levels). We conclude that the isolated effect of PKA on SR Ca2+ release is an increase in maximal rate of release and faster turn-off of release (such that integrated SR Ca2+ release is unchanged). The increased amount of SR Ca2+ release normally seen with ISO depends primarily on increased ICa trigger and SR Ca2+ load, whereas faster release kinetics may be the main result of RyR phosphorylation.

Original languageEnglish (US)
Pages (from-to)463-480
Number of pages18
JournalJournal of Physiology
Volume556
Issue number2
DOIs
StatePublished - Apr 15 2004
Externally publishedYes

Fingerprint

Excitation Contraction Coupling
Isoproterenol
Cardiac Myocytes
Protein Kinases
Ryanodine Receptor Calcium Release Channel
Cyclic AMP-Dependent Protein Kinases
Muscle Cells
Transgenic Mice
Phosphorylation
Rabbits

ASJC Scopus subject areas

  • Physiology

Cite this

Modulation of excitation-contraction coupling by isoproterenol in cardiomyocytes with controlled SR Ca2+ load and Ca2+ current trigger. / Ginsburg, Kenneth S; Bers, Donald M.

In: Journal of Physiology, Vol. 556, No. 2, 15.04.2004, p. 463-480.

Research output: Contribution to journalArticle

@article{bc04c47dcdcf41789a971fe3b56f11b1,
title = "Modulation of excitation-contraction coupling by isoproterenol in cardiomyocytes with controlled SR Ca2+ load and Ca2+ current trigger",
abstract = "Cardiac Ca2+ transients are enhanced by cAMP-dependent protein kinase (PKA). However, PKA-dependent modulation of ryanodine receptor (RyR) function in intact cells is difficult to measure, because PKA simultaneously increases Ca2+ current (ICa), SR Ca2+ uptake and SR Ca2+ loading (which independently increase SR Ca2+ release). We measured ICa and SR Ca2+ release ± 1 μm isoproterenol (ISO; isoprenaline) in voltage-clamped ventricular myocytes of rabbits and transgenic mice (expressing only non-phosphorylatable phospholamban). This mouse model helps control for any effect of ISO-enhanced SR uptake on observed release, but the two species produced essentially identical results. SR Ca2+ load and ICa were adjusted by conditioning. We thus evaluated PKA effects on SR Ca2+ release at constant SR Ca2+ load and ICa trigger (with constant unitary ICa). The amount of SR Ca2+ release increased as a function of either ICa or SR Ca2+ load, but ISO did not alter the relationships (measured as gain or fractional release). This was true over a wide range of SR Ca2+ load and ICa. However, the maximal rate of SR Ca2+ release was ∼50{\%} faster with ISO (at most loads and ICa levels). We conclude that the isolated effect of PKA on SR Ca2+ release is an increase in maximal rate of release and faster turn-off of release (such that integrated SR Ca2+ release is unchanged). The increased amount of SR Ca2+ release normally seen with ISO depends primarily on increased ICa trigger and SR Ca2+ load, whereas faster release kinetics may be the main result of RyR phosphorylation.",
author = "Ginsburg, {Kenneth S} and Bers, {Donald M}",
year = "2004",
month = "4",
day = "15",
doi = "10.1113/jphysiol.2003.055384",
language = "English (US)",
volume = "556",
pages = "463--480",
journal = "Journal of Physiology",
issn = "0022-3751",
publisher = "Wiley-Blackwell",
number = "2",

}

TY - JOUR

T1 - Modulation of excitation-contraction coupling by isoproterenol in cardiomyocytes with controlled SR Ca2+ load and Ca2+ current trigger

AU - Ginsburg, Kenneth S

AU - Bers, Donald M

PY - 2004/4/15

Y1 - 2004/4/15

N2 - Cardiac Ca2+ transients are enhanced by cAMP-dependent protein kinase (PKA). However, PKA-dependent modulation of ryanodine receptor (RyR) function in intact cells is difficult to measure, because PKA simultaneously increases Ca2+ current (ICa), SR Ca2+ uptake and SR Ca2+ loading (which independently increase SR Ca2+ release). We measured ICa and SR Ca2+ release ± 1 μm isoproterenol (ISO; isoprenaline) in voltage-clamped ventricular myocytes of rabbits and transgenic mice (expressing only non-phosphorylatable phospholamban). This mouse model helps control for any effect of ISO-enhanced SR uptake on observed release, but the two species produced essentially identical results. SR Ca2+ load and ICa were adjusted by conditioning. We thus evaluated PKA effects on SR Ca2+ release at constant SR Ca2+ load and ICa trigger (with constant unitary ICa). The amount of SR Ca2+ release increased as a function of either ICa or SR Ca2+ load, but ISO did not alter the relationships (measured as gain or fractional release). This was true over a wide range of SR Ca2+ load and ICa. However, the maximal rate of SR Ca2+ release was ∼50% faster with ISO (at most loads and ICa levels). We conclude that the isolated effect of PKA on SR Ca2+ release is an increase in maximal rate of release and faster turn-off of release (such that integrated SR Ca2+ release is unchanged). The increased amount of SR Ca2+ release normally seen with ISO depends primarily on increased ICa trigger and SR Ca2+ load, whereas faster release kinetics may be the main result of RyR phosphorylation.

AB - Cardiac Ca2+ transients are enhanced by cAMP-dependent protein kinase (PKA). However, PKA-dependent modulation of ryanodine receptor (RyR) function in intact cells is difficult to measure, because PKA simultaneously increases Ca2+ current (ICa), SR Ca2+ uptake and SR Ca2+ loading (which independently increase SR Ca2+ release). We measured ICa and SR Ca2+ release ± 1 μm isoproterenol (ISO; isoprenaline) in voltage-clamped ventricular myocytes of rabbits and transgenic mice (expressing only non-phosphorylatable phospholamban). This mouse model helps control for any effect of ISO-enhanced SR uptake on observed release, but the two species produced essentially identical results. SR Ca2+ load and ICa were adjusted by conditioning. We thus evaluated PKA effects on SR Ca2+ release at constant SR Ca2+ load and ICa trigger (with constant unitary ICa). The amount of SR Ca2+ release increased as a function of either ICa or SR Ca2+ load, but ISO did not alter the relationships (measured as gain or fractional release). This was true over a wide range of SR Ca2+ load and ICa. However, the maximal rate of SR Ca2+ release was ∼50% faster with ISO (at most loads and ICa levels). We conclude that the isolated effect of PKA on SR Ca2+ release is an increase in maximal rate of release and faster turn-off of release (such that integrated SR Ca2+ release is unchanged). The increased amount of SR Ca2+ release normally seen with ISO depends primarily on increased ICa trigger and SR Ca2+ load, whereas faster release kinetics may be the main result of RyR phosphorylation.

UR - http://www.scopus.com/inward/record.url?scp=2342466724&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=2342466724&partnerID=8YFLogxK

U2 - 10.1113/jphysiol.2003.055384

DO - 10.1113/jphysiol.2003.055384

M3 - Article

C2 - 14724205

AN - SCOPUS:2342466724

VL - 556

SP - 463

EP - 480

JO - Journal of Physiology

JF - Journal of Physiology

SN - 0022-3751

IS - 2

ER -