Normal contractions triggered by ICa,L in ventricular myocytes from rats with postinfarction CHF

Ivar Sjaastad*, Janny Bøkenes, Fredrik Swift, J. Andrew Wasserstrom, Ole M. Sejersted

*Corresponding author for this work

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

Attenuated L-type Ca2+ current (ICa,L), or current-contraction gain have been proposed to explain impaired cardiac contractility in congestive heart failure (CHF). Six weeks after coronary artery ligation, which induced CHF, left ventricular myocytes from isoflurane-anesthetized rats were current or voltage clamped from -70 mV. In both cases, contraction and contractility were attenuated in CHF cells compared with cells from shamoperated rats when cells were only minimally dialyzed using high-resistance microelectrodes. With patch pipettes, cell dialysis caused attenuation of contractions in sham cells, but not CHF cells. Stepping from -50 mV, the following variables were not different between sham and CHF, respectively: peak ICa,L (4.5 -± 0.3 vs. 3.8 ± 0.3 pApF-1 at 23°C and 9.4 ± 0.5 vs. 8.4 ± 0.5 pApF-1 at 37°C), the bell-shaped voltage-contraction relationship in Cs+ solutions (fractional shortening, 15.2 ± 1.0% vs. 14.3 ± 0.7%, respectively, at 23°C and 7.5 ± 0.4% vs. 6.7 ± 0.5% at 37°C) and the sigmoidal voltage-contraction relationship in K+ solutions. Caffeine-induced Ca2+ release and sarcoplasmic reticulum Ca2+-ATPase-to-phospholamban ratio were not different. Thus CHF contractions triggered by ICa,L were normal, and the contractile deficit was only seen in undialyzed cardiomyocytes stimulated from -70 mV.

Original languageEnglish (US)
Pages (from-to)H1225-H1236
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume283
Issue number3 52-3
DOIs
StatePublished - 2002

Keywords

  • Caffeine
  • Congestive heart failure
  • Electrophysiology
  • L-type Ca current
  • Myocardial infarction
  • Phospholamban
  • Sarcoplasmic reticulum Ca ATPase

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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